EQUIPMENT

Food canning equipment for making high-acid foods such as jams, jellies, pickles, relishes or chutneys is very simple as the heat requirements are only 212° F, 100° C. Any suitable size pot with a rack and cover becomes the water bath canner. Glass jars, jar lifter, thermometer, timer, wide mouth funnel, all those little items can be readily found in the kitchen. But, when metal cans are involved, the canning becomes more difficult as one needs to obtain can sealer and acquire new knowledge about the seaming process. There is not much danger involved in processing jams or pickles.

However, processing low-acid foods such as meat, poultry, fish and vegetables elevates the art of canning to a much higher level, especially when cans are employed. Low-acid foods must be processed at 240-150° F, 116-121° C and that requires the pressure canner. A good understanding of can sealer, basic adjustments and knowledge of canning defects is necessary. The rules must be strictly observed as improperly canned low-acid food can become dangerous.

Glass Jars

When Nicolas Appert struggled with his first attempts at canning, neither glass jars nor tin cans were around, so he was using wide mouth bottles and corks which were secured with wire. John Mason patented the continuous-thread closure on November 30, 1858. In 1883 William Charles Ball and his brothers switched over from tin containers to glass containers for storing lard and oil. In 1886 they started to use glass containers for storing fruits. In 1903 Alexander Kerr started to use wide mouth glass jars. Later in 1915 he invented a smaller, flat metal disk with a permanent composition gasket. His two-part lid system transformed home canning safety and is still in use today. Glass jar is made from three separate molds: finish, body and bottom, which are then molded together. The connection is known as mold seam and may be mistaken for a crack in the glass. Each part has its own mold seam and they may or may not be aligned in a straight line.

The basic parts of a glass jar.

Use only standard jars intended for home canning. Never use jars from commercial food products. Regular and wide-mouth Mason-type, threaded, home-canning jars with self-sealing lids are the best choice. They are available in 1/2 pint, pint, 1-1/2 pint, quart, and 1/2 gallon sizes. The standard jar mouth opening is about 2? inches. Wide-mouth jars have openings of about 3 inches making them more easily filled and emptied. Half-gallon jars may be used for canning high acid juices. Regular-mouth decorator jelly jars are available in 8 and 12 ounce sizes. With careful use and handling, Mason jars may be reused many times, requiring only new lids each time. When jars and lids are used properly, jar seals and vacuums are excellent and jar breakage is rare.Most commercial pint and quart size mayonnaise or salad dressing jars may be used with new two piece lids for canning acid foods. However, you should expect more seal failures and jar breakage. Seemingly insignificant scratches in glass may cause cracking and breakage while processing jars in a canner. Mayonnaise-type jars are not recommended for use with foods to be processed in a pressure canner because of excessive jar breakage. Other commercial jars with mouths that cannot be sealed with two-piece canning lids are not recommended for use in canning any food at home.

Glass Jar Types

There are three types of glass jars and closures currently used in food packaging:

1. The continuous-thread jar.

2. The twist-on jar.

3. The press-and-twist jar.

Continuous-Thread Jar With Single Lid

The jar and lid are both threaded in one continuous bead around the entire circumference of the opening; also referred to as "screw-on". There is less likelihood of over-tightening a screw-on closure. Continuous-thread jar may have a one part lid, for example mayonnaise jar or it may have closure consisting of two parts: a lid and a screwband, for example a typical canning Mason jar.

All types of jars can have a vacuum indication button built into the lid.

Many believe that a canning jar must be embossed on the sides with the word Mason, Ball or Kerr. Well, what is the real Mason jar? Any jar with a continuous-thread closure will do the same job as long as it is made strong enough to withstand the thermal shocks encountered in the canning process.

Continuous-Thread Jar With Two-Piece Lid

The advantage of glass jars with two-part lids lies in the fact that those jars have been around in the USA for so long that they have become an unwritten standard in home canning. There are three sizes to choose from: 1/2 pint, pint

and quart, two lid sizes will fit all jars, and the jars can have a regular or wide mouth opening. The lids come with one universal sealing compound and the jars have been perfected over the years. If used properly they create a perfect seal every time.

It is our recommendation to use wide mouth jars for canning meat as many products will hold their shape better when removed from a jar, for example meat loaf. Then they can be browned or roasted and they will look much better on a plate. There are meats that are eaten cold, for example head cheese or meat jelly. They may even have food decoration in the bottom which will be on top of the piece when it is flipped over. You can use regular jars for soups, beef stews or products which are made of many smaller components, for example chili con carne and beans. However, canning is simpler when only wide mouth openings are chosen. In addition, the same diameter lid and screwband fit both, pint and quart size jars.

Lid Selection, Preparation and Use

The common self-sealing lid consists of a flat metal lid held in place by a metal screw band during processing. The flat lid is crimped around its bottom edge to form a trough, which is filled with a colored gasket compound. When jars are processed, the lid gasket softens and flows slightly to cover the jar-sealing surface, yet allows air to escape from the jar. The gasket then forms an airtight seal as the jar cools. Gaskets in unused lids work well for at least 5 years from date of manufacture. The gasket compound in older unused lids may fail to seal on jars. Buy only the quantity of lids you will use in a year. To ensure a good seal, carefully follow the manufacturer's directions in preparing lids for use. Examine all metal lids carefully. Do not use old, dented, or deformed lids, or lids with gaps or other defects in the sealing gasket. Use new lids every time.

Self-sealing lid and screwband (top).

Those closures are commonly used for

water bath and pressure canners.

The lid goes on top of a jar and is held in place by the screw band that goes over it. The jar lids are usually heated in hot water and kept hot until ready to use. The screw band is secured finger tight as it does not play a major role in the sealing process. If rings are too loose, liquid may escape from jars during processing and seals may fail. If rings are too tight, air cannot vent during processing and food will discolor during storage. Over tightening also may cause lids to buckle and jars to break, especially with raw-packed, pressure-processed food. When a jar is processed the sealing compound softens and covers the rim surface of the jar. However, it remains soft enough to allow the building air pressure to escape from the jar. As the jar cools, the compound hardens and the gasket forms an airtight seal. The slow hardening of the gasket is the reason why processed jars are left undisturbed for 12 hours to cool down. After cooling, the jars are inspected for a tight seal. The metal screw bands have served their purpose and may be left on the jars or removed and used in the next operation. Do not retighten lids after processing jars. As jars cool, the contents in the jar contract, pulling the self-sealing lid firmly against the jar to form a high vacuum. Screw bands are not needed on stored jars. They can be removed easily after jars are cooled. When removed, washed, dried, and stored in a dry area, screw bands may be used many times. If left on stored jars, they become difficult to remove, often rust, and may not work properly again.

Twist-On Jar

Lug is the closure system where the container has multiple threads and the lid has an equal number of lugs or tabs that grip the corresponding threads; also known as "twist-on". There may be three to six lugs depending on the diameter of the cap. Twist-on closures are mainly used by commercial producers, although they are available online as well. In their guides, the USDA mentions only glass with two part lids for home canning, however, all commercial products are canned in jars with a single lid only. Twist on jars (lug type) can be processed much faster by modern machines as the lid is closed with a part turn only. The lug closure (twist cap) can be easily removed and forms a good reseal for storage. Homeowners in Europe use single lid closures and most of them are not familiar with American style two-part lid.

Be aware that standard one-piece lids are manufactured for hot-fill temperatures (around 180° F). Then, there are lids manufactured for hot water bath (212° F, 100° C) and the lids that can be used in pressure canners (over 212° F, 100° C). The conclusion: do your homework first, then pick up the lid suitable for your application. Continuous thread single closure jars are commonly used in Europe for hot filling acidic foods such as jams or jellies. After the jar is filled, it is inverted for for a few minutes, then left to cool by itself. Inverting the jar allows plastisol make contact with hot contents which softens the sealing compound. Upon cooling the vacuum forms inside and the jar is sealed.

Fillmorecontainer, www.fillmorecontainer.com carries single piece canning lids with a vacuum indicating button for pressure canning. Those lids incorporate a sealing compound which has been designed for processing at higher temperatures.

Recommended Glass Jars for Home Use

Containers larger than quart glass jars or No. 3 cans are not recommended for home use because of difficulty of thorough heat processing. As a result some parts of the food might not be sufficiently heated and may not kill bacterial spores.

Testing Sealed Jars

Most two piece lids will seal with a "pop" sound when cooling. When the canning jars have cooled down, test the lid. A canning jar is properly sealed if the lid is curved down or remains so when pressed. If it springs back and makes a clicking sound it is not properly sealed.

Fresh unprocessed lid has a little curved up nipple in the middle.

Heat processed and properly sealed lid is curved down.

Another method is to tap the center of the lid with a spoon. A clear ringing sound means a good seal. A dull sound signifies that a jar does not have a tight seal or that the food is touching the lid. Hold the jar and look at it. If no food is touching the lid, the jar does not have a tight seal and cannot be stored. When the jars have completely cooled, the screw bands are removed. Due to humidity they may rust during storage making them difficult to remove. The bands do not form the seal, the canning lids do. Remove the screw bands, wash, dry and store them until needed again. Check seals. Improperly sealed jars can be reprocessed within 24 hours using a new sterilized lid and the same processing time. If they are not remade, they should be refrigerated and used within 1 month.

Metal Cans

The number of cans on the market is overwhelming and choosing the right can may be an intimidating task for a newcomer. Metal cans come in different shapes and sizes. The can sizes used in industry in the U.S.A. are derived from nominal outside dimensions. While such dimensions may be expressed in inches, the custom is to use a conventionalized method in which three-digit numbers are used to express each dimension. The first digit indicates the number of whole inches in a dimension, and the second and third digits indicate the fractional inches as sixteenths of an inch. Thus:

211 x 400 means 2-11/16 x 4 inches

307 x 409 means 3-7/16 x 4-9/16 inches

404 x 414 means 4-4/16 x 4-14/16 inches

In oval cans, outside dimensions are used, the dimensions of the opening stated first, followed by the height. The inches and sixteenths of an inch system is the same as with round cans. An example: 402 x 304 x 300, means that the oval opening is 4-2/16 x 3-4/16 inches and the height is 3 inches. Metric system is much simpler and the sizes are defined in millimeters, for example:

round cans - 73 x 55 mm, 99 x 63 mm, 99 x 119 mm

oval cans - 90 x 103 x 217 mm

Capacity, of course, is defined in milliliters.

There are cans which are suitable for certain applications, for example beverage cans, beer cans, soup cans or meat and fish cans. Food cans are lined up with enamel coating inside to prevent any reactions between metal and food which may affect the flavor of the product. The most popular can is the basic round can, constant diameter, parallel walls, which is a cylinder. However, the tapered cans are of more interest to a homeowner. The tapered can has tapered body walls so that the diameter of the two ends is different. The advantage of this design that the cans can be nested during shipping, resulting in smaller packages and lower costs. They can also be stacked easily in storage. A hobbyist must consider the can size he intends to use with the size of the can sealer that can seal it. Metal cans are expensive when bought by the dozen, however, the price drastically drops when ordering a few hundred.

The capacity of can is given in ounces of water at 6° F, 20° C.

1 US fluid ounce = 29.57 ml

1 inch = 25.4 mm

Metal can sizes used in industry in the U.S.A. are derived from nominal outside dimensions. Measurements are made of the empty round can before seaming on the packers' end. Using the outside diameter of the No. 2 can for calculating cylinder volume will tell us that the can is able to hold 23.5 liquid ounces. However, in reality the can will hold only 20.5 ounces of water. Using the inside diameter will provide the correct number. There are can-shaped containers made from aluminum foil and plastic laminates, there are rectangular-shaped cans and retortable pouches. Cans with easy-to-open rings on the lid are very popular. They all, however, require specialized equipment which is not available to a hobbyist. For home canning it is difficult to beat a round cylindrical can.

Metric size cans use the inside diameter to describe the can. For example No. 2 can, 307 x 409 converts to 87 (outside dia) x 115 mm, however, it is classified as 83 (inside dia) x 115 mm can in Europe. Remember that every time you use a can with a different diameter, you need a different size chuck in your sealer. When buying a sealer you have to specify the size of the can you will be sealing and the sealer comes with this size chuck and spacer pre-installed. Let's assume you have a 225 model sealer equipped for No. 2 can (307 diameter) and you decide that you want to can your salmon in smaller No. 1 cans (211 diameter). Well, you have two options: buy another expensive 225 sealer equipped for No. 1 can, or buy an additional chuck for No. 1 can. Needless to say, you have to switch over the chucks yourself.Some machines like Ives-Way include different size chucks so you can seal a variety of different cans.

Recommended Cans for Home Use

Larger cans can be used for packing dry foods (peas, beans, coffee beans) that don't have to be sterilized. Commercial producers can afford to use containers of any size or shape as the recipes they use are drawn by professionally trained individuals. In addition, those plants work under the direct supervision of Food Safety and Inspection Service inspectors and every recipe is thoroughly checked for safety. A home canner should follow guidelines for canning food in round cans or glass jars.

Types of Cans

Most cans are produced from tinplate. Tinplate is a thin sheet of steel, about 1/128-1/64 inch (0.2-0.4 mm) which is electrolytically coated with a very thin layer of tin on both sides. In addition, the interior of the cans is coated with a synthetic compound to prevent chemical reaction of the tinplate with the food.

The Three-Piece Cans

Three-piece steel cans are composed of the body, the bottom end and the top end (lid). The body is made of a sheet of tinplate, the sheet is made into a cylindrical shape and the ends slightly overlap. Then the ends are soldered and the soldering area is covered inside with a strip of coating for protection.

After the body of the can is formed, one end is applied by the manufacturer, called the manufacturer's end, and the other called the canner's end, is applied by the canner using can sealer.

The Two-Piece Cans

The bottom end and the body are formed from one sheet of metal by stamping or a combination of stamping and deep drawing. It is easy to recognize a two-piece can because it has no seam at the bottom.

There is a limitation to how much steel can be drawn and usually the side walls are twice the diameter of the can (1:2), for example, a popular 1/2 lb. tuna fish can is a two-piece drawn can of 87 x 45 mm.

Aluminum cans offer better deep-drawing capability so the walls of two-piece cans can be longer. They are more expensive, however, they offer benefits of low weight, an excellent heat transfer conductivity and strong resistance to corrosion.

Tapered Cans

Two part tapered cans are the real space savers as they can be stacked inside one another. This lowers costs of shipping and facilitates storage. There are two tapered cans which are very popular for canning salmon: 307 x 200, 8 oz, and 301 x 408, 16 oz. The fact that there is only one seam (the lid) to worry about makes them especially attractive for home applications.

Easy to Open Cans

Easy to open cans are extremely popular, however, they require specialised sealing equipment which is not available to a home owner.

Fish cans are usually made from aluminum and they come in many shapes and sizes. Commercial producers need to create their own processing times, something a home owner is not able to do.

Glass Jar or a Metal Can, What's Better?

Commercial producers use metal cans not because they are pretty, they use them because they hold many advantages over glass jars. They can be processed faster, they don't break so easily and they are easier to cool resulting in a higher quality of the product.

Glass Jar

• • Information and recipes can be found in other publications and on the Internet.

  • Glass jars available in every large supermarket and online. Jars are standardized, almost all home canning is done in 2-part lid mason jars. The closure is not popular in Europe where most canning is done with a twist-on lid.

  • Canning in glass requires little knowledge and is easy to do. A perfect seal is assured and is easily verified by visual inspection and simple testing.

  • Contents are visible.

  • Reusable, only lids need to be replaced.

  • No specialized equipment is needed as the canning operation is performed with a pressure canner, glass jars and common kitchen tools.

  • Inexpensive to purchase in low quantity.

  • Safer method as there are less chances for error.

  • Due to the shape of the jar, solid shaped products will break upon removal.

  • Glass breaks easy.

  • Glass breaks when exposed to a rapid change of temperature; after thermal treatment the jars are left to cool by themselves. Should not be handled during cooling (12 hours).

  • Seal needs time to harden.

  • An additional cooking takes place during initial cooling of the jars. Overcooking results in a poor texture of the food.

  • Jars should be kept in dark areas otherwise there will be change in food color and the fats will go rancid.

  • When cooling temperature drops to 122-150° F, 50-66° C range, thermophillic spoilage bacteria which survived the thermal treatment can start growing again.

  • Commercial producers tend to process foods as fast as possible and at lowest possible temperatures. Glass jars are not suited for that.

  • Glass jars are heavy. Glass does not corrode, but the screwbands do.

  • Metal Can

  • Almost no written information for a hobbyist. A few expensive technical textbooks for people employed in the canning industry. Little information on the Internet.

  • Metal cans are available only online. There are about 25 commonly used cans and choosing one may be a confusing task.

  • More knowledge is required by the operator. Some basic mechanical skills are needed to change over chucks and perform simple adjustments.

  • Contents are not visible.

  • Used only once.

  • A can sealer machine is required. A different chuck must be installed to accommodate a can of different diameter. A spacer must be installed when using a can of a different length. Some adjusting is required.

  • Expensive when buying a few cans. Cheap in large quantities.

  • Safe method, providing at home canners are willing to learn operating of a can sealer.

  • Solid blocks such as luncheon meat or meat jelly can be removed intact.

  • Strong. Packing machine can process thousands of cans per minute, something that is impractical using jars.

  • Can be cooled after thermal treatment. Can be handled at any time.

  • Seal is set after sealing.

  • Rapid cooling after thermal treatment stops cooking.

  • May be exposed to lite.

  • Can be rapidly cooled to 95° F, 35° C eliminating bacterial growth and additional cooking.

  • Hundreds of cans can be sealed every minute. After thermal process cooling is accomplished without a delay in the same retort.

  • Cans are light. The outside surface will corrode in humid conditions.

Water Bath Canner (suitable for high acid foods only)

The main advantage of a water bath canner is that any large pot with a lid that is tall enough to accommodate jars is suitable for canning. Most water bath canners hold seven quart jars or eight to nine pints. Although pressure canners may also be used for processing acid foods (meat, fish, vegetables) boiling water canners are recommended for this purpose because they are faster. A pressure canner would require from 55 to 100 min. to process a load of jars, while the total time for processing most acid foods in boiling water varies from 25 to 60 minutes. A boiling-water canner loaded with filled jars requires about 20 to 30 min. of heating before its water begins to boil. A loaded pressure canner requires about 12 to 15 minutes of heating before it begins to vent; another 10 minutes to vent the canner; another 5 minutes to pressurize the canner; another 8 to 10 minutes to process the acid food; and, finally, another 20 to 60 minutes to cool the canner before removing jars.

Boiling water canners are used to process acid foods at a boiling temperature (212° F, 100° C). The boiling water temperature remains constant in a particular geographical location as the height of the air column above the canner regulates the pressure. At higher or lower altitudes, the height (and the weight) of the air column will change as well and there will be a different amount of pressure applied against the boiling water. At high latitudes there is a less pressure and consequently water molecules need less energy (heat) to break loose from the surface.

Canner, jar, rack and 2-inches water over the top.

In a bath water canner the lid rests loosely on top of the canner. In a big pot like the one in the photo above, the lid is rather heavy. This means that there would be occasional build-ups in pressure inside until the pressure is strong enough to lift up the lid. This will push the temperature up by a few degrees. It is possible to process jars in a canner without a lid as at sea level the temperature of boiling water remains constant at 212° F, 100° C. However, there would be significant water loss due to evaporation and the jars might become uncovered. To compensate for that more boiling water will have to be added to the pot when needed. It is much simpler to use a lid. Foods which are processed by this method are: fruits, pickles, relishes, tomatoes, jams, jellies, preserves, marmalades, butters, syrups and honey. A water bath canner is a large covered cooking pot with a rack. It has to be deep enough to cover the jars with 1-2 inch of boiling water. The rack keeps the jars from touching the bottom of the canner and allows the water to circulate freely under them. A flat bottom must be used on an electric range. Either a flat or ridged bottom can be used on a gas burner. To ensure uniform processing of all jars with an electric range, the canner should be no more than 4 inches wider in diameter than the element on which it is heated.

Two layers of jars can be processed at once, as long as the canner is tall enough. Place a small wire rack between the layers to facilitate the circulation of water. Make sure that there is at least 1 inch of water over the tops of all jars.

Using a Boiling Water Canner

Before you start preparing food, fill the canner half full with water.

Preheat water to 140° F (60° C) for raw-packed foods and to 180° F (82° C) for hot-packed foods.

Load filled jars, fitted with lids, one at a time into the canner and place on the rack OR load filled jars into the canner rack and use the handles to lower the rack into the water. Keep the jars upright.

NOTE it is common to sterilize jars before processing, however they do not need to be sterilized if they will be filled with food and processed in a water bath canner for 10 minutes or more. Jars that will be filled with food and processed in a water bath canner for less than 10 minutes must be sterilized first by boiling them in hot water for 10 minutes before filling them.

WARNING a water bath canner is not suitable for canning low acid foods such as meats, poultry, fish and vegetables.

Pressure Canners

Low-acid foods must be processed in a pressure canner to be free of botulism risks.

To destroy microorganisms in low-acid foods processed with a pressure canner, you must process the jars using the correct time and pressure specified for your altitude. The food may spoil if you fail to select the proper process times for specific altitudes, fail to exhaust canners properly, process at lower pressure than specified, process for fewer minutes than specified, or cool the canner with water. Small pressure canners hold four-quart jars; some large pressure canners hold 18 pint jars in two layers, but hold only seven quart jars. Pressure saucepans with smaller volume capacities are not recommended for use in canning. Small capacity pressure canners are treated in a similar manner as standard larger canners, and should be vented using the venting procedures. Modern pressure canners are lightweight, thin walled kettles; most have turn-on lids. They have a jar rack, gasket, dial or weighted gauge, an automatic vent/cover lock, a vent port (steam vent) to be closed with a counterweight or weighted gauge, and a safety fuse. Pressure does not destroy microorganisms, but high temperatures applied for an adequate period of time do. A pressure canner is separated from the outside air by a forcefully shut lid.

The success of destroying all microorganisms capable of growing in canned food is based on the temperature obtained in pure steam, free of air, at sea level. At sea level a canner set to a gauge pressure of 10-1/2 lbs provides an internal temperature of 240° F (116° C).

It is the amount of heat applied to the unit that regulates pressure.

If heat is continuously applied and the steam is prevented from escaping, the increasing pressure will reach the point when the vessel will explode. To prevent that a pressure canner employs an adjustable pressure regulator, and of course, a safety valve (overpressure plug) which will open when the pressure reaches a dangerous level. As the pressure is changing within the unit, the pressure regulator weight jiggles and sputters which is simply a process of constantly building up and releasing pressure to maintain the setting on the pressure regulator weight. Allow the canner to cool at room temperature until it is completely depressurized. Pressure canners use two types of pressure gauges:

• Weighted gauge

• Dial gauge

It should be noted that a dial gauge needs to be checked for accuracy every year. Some canners come with a rubber sealing gasket and others make a tight fit without employing gaskets at all. All pressure canners come with detailed instructions for their use. Weighted gauge has three settings: 5 PSI, 10 PSI and 15 PSI

Pressure canner, the lid is secured tight. In this

All-American 921 model, the six clamps hold the

cover air-tight.

Two layers of jars can be processed at once, as long as the pressure canner is tall enough. Place a small wire rack between the layers to facilitate the circulation of steam. Make sure that there is 2-3" of water in the bottom.

Presto Pressure Canners

National Presto Industries has been making Presto Pressure Canners for over 50 years. Presto Pressure Canners are made of high quality aluminum for great heat distribution. Don't confuse the pressure canner with smaller pressure cookers, also made by PrestoÆ

PrestoÆ pressure canners operate on a dial gauge principle. The dial gauge does not regulate the amount of pressure, it is just an indicator of the pressure inside. The pressure is controlled by increasing or decreasing heat supply. What is called the pressure regulator is actually a safety device to prevent pressure in excess of 15 pounds to build in the canner. The regulator sits loosely on top of the vent pipe, right to the dial gauge in the above photo. The real safety valve known as the overpressure plug is made of black rubber and can be seen on the left behind the dial gauge. Once the pressure increases to 15 PSI the pressure regulator starts to rock releasing pressure and maintain the setting at 15 PSI. If for any reasons the vent pipe becomes clogged, the regulator will not sense it so the pressure will increase well over 15 PSI. However, the overpressure plug will pop out releasing the pressure. Check the vent pipe every time when the cover is placed on..

There is a clever device called an air vent which is basically a cover lock. When the pressure start to build up, the air vent pops out and automatically exhausts air from the canner. At the same time it engages with the bracket on the inside of the canner preventing the cover from being opened when there is pressure in the canner. It acts as a visual indication of pressure in the canner.

The heat is on, the air from the canner escapes through the vent pipe, which is not covered with a pressure regulator yet. Once the air exhausts out, the pressure regulator will be placed on top of the vent pipe where it will sit loosely. There is no indication of the dial yet, but the raising pressure and escaping air have already pushed the air vent up.

When the end of the processing time is reached, the heat is turned off. The canner should be removed from the electrical burner to prevent unnecessary heating, however, lift it carefully up, otherwise you may scratch a surface of the glass top stove. If you are using a gas burner, just turn off the heat. The canner must cool by itself until the dial reads 0 psi and the air vent drops down. Now, the pressure regulator can be taken off the vent pipe and the cover can be removed.

WARNING escaping steam can scald you and the pressure control may be hot. Protect your hands with oven gloves and tilt the cover so steam escapes away from you. Using a jar lifter remove the jars one at a time. Place the hot jars on dry towels or a cooling rack. Let them sit undisturbed for 12 hours. Remove the screwbands and test the jars.

All American Pressure Canners

Established in 1909, Wisconsin Aluminum Foundry makes top quality pressure canners and can sealers. It is a heavy duty canner, without a rubber seal, operating on the weighted gauge principle.

When the pressure canner reaches the proper temperature, the regulator weight will jiggle audibly and some steam will be released. The pressure will be automatically maintained for proper pressure cooking.

Mirro Pressure Canners

Mirro pressure canners work on a weighted gauge principle. There is no dial pressure indicator. Use canners that are equipped with weighted gauge (5, 19, 15 lb) only. Do not try to can in single-control model. The weighted gauge should jiggle about 2-3 times per minute. All pressure canners come with a rack. Placing jars directly on the bottom of the canner will likely crack them. Keep the jar upright at all times. Tilting the jar could cause food to spill into the sealing gasket of the lid and produce an imperfect seal. The jars may be stacked in the canner on two levels. Place another rack on top of the first row, then add more jars on top or offset the jars by placing one across two others.

Storage of the Canner

Clean and dry your canner. Store it with crumpled newspapers or paper towels in the bottom and around the rack. Place the lid upside down on the canner to protect the gauge, vent and sealing ring. Storing cans at high temperatures may result in flat sour - a type of spoilage where the can ends remain flat but the food turns sour. It is caused by heat loving bacteria which grow at 150-160° F, 66-71° C. Inadequate cooling after canning or storage at high temperatures promotes such spoilage.

Commercial Pressure Retorts

The industry uses the term "retort." Retort can process a few hundred or many thousands cans at one operation. It has to comply with the government regulations, for example each retort must have a temperature indicating device (thermometer) and the temperature recording chart. A pressure canner is a small canner used at home. The main difference between a pressure canner and a retort is the cooling capability of a commercial vessel. At the end of a thermal process the compressed air is injected inside and the retort is flooded with cold water. The cold water immediately lowers the temperature of the product and the compressed air prevents cans from buckling up and the contents of glass jars from boiling over. The temperature of the glass jars must be lowered gradually to prevent the glass from breaking due to the thermal shock. This pessurizing/cooling process allows for a precise control of cooking time and results in a higher quality, longer shelf life product that can be produced at home.

Commercial retorts can be classified into the following groups:

• Still Steam Retorts (vertical or horizontal).

• Still Steam Retorts with Overpressure.

• Hydrostatic Retorts.

• Continuous Rotary Retorts.

• Batch Agitating Retorts.

In addition there are Asceptic Processing and Packaging Systems. Those systems are used for processing liquid foods which are pumped throughout the system. The asceptic system consists of three distinctive areas, all kept in sterile conditions:

1. Equipment is sterilized.

2. Food is cooked to the commercial sterility stage and stored in a sterile tank.

3. Food is packed into sterile containers in a sterile room.

Vertical still steam retort.

Like a home pressure canner, the vertical retort is loaded from the top. A wire basket holding hundreds of cans is lowered inside the retort.

Can Sealers

Can sealer hermetically seales cans. The process of attaching the can end (lid) to the can body is called double seaming. This seam is formed by mechanically interlocking the outside end of the lid known as the "curl" with the top part of the can body known as the "flange."

Curl and flange form double seam.

A double seam is formed by joining the body of the can with the lid, which in trade is usually referred to as the cover or the end. The body flange and the curl of the lid interlock together and form a strong mechanical joint. However, this joint, although strong is not yet airtight and cannot be considered to be a hermetically formed closure. A sealing compound is attached to the curl of the lid. Compressing the lid and can body together forces the soft compound sealant to flow and fill any little spaces that might be present in a double seam and the combination of a double seam and the dealing compound makes a hermetically (airtight) formed closure. The amount of the compound sealer and its composition depends on the style of container and the method of sterilization. Each double seal consists of five layers of metal interlocked together: three from the lid and two from the body of the can.

A cover carries a sealing compound inside of its curl.

Curl and flange form double seam.

A double seal is a strong mechanical structure containing five layers of metal together, three layers of the lid and two layers of the can body.

Basic parts of a sealer

Each sealer or "seamer machine" (industry name) has a:

Base plate (turntable) - provides support for the can body.

Seaming chuck - snugly holds the top of the can (lid) and acts as a support surface for the pressure of the rollers.

A set of operation rollers - the first roller interlocks the lid with the body of the can. The second roller tightens and irons out the seam.

Sealing is a critical operation in the can processing. It must protect the contents of the can during thermal processing, and it must isolate canned food from microorganisms and air during storage.

Compression

Compression provides the necessary force for holding the can against the chuck and to feed the flange of the body into the first roller. Every closing machine has a base plate and a chuck. The snugly fitting chuck holds the lid in place and provides support for the seaming rolls pressure. The base plate is spring loaded and pushes the can up against the chuck.

Chuck

All round cans are classified with diameter x height dimensions, for example 307 x 409 and 307 x 200. Every time the diameter (the first number) changes, a proper chuck must be installed. In the above example the cans have different diameters so 307 and 301 chucks must be used. When a crank handle is turned, a set of gears transfers the movement to the chuck which starts turning. The grooves on the chuck force the lid to turn as well. The chuck fits snugly into the lid. Its disc has many groves on its side and those grooves lock the lid.

Turntable

Turntable, also known as base plate, is a free spinning disc that supports the can. The chuck propels the lid that sits on top of the body of the can. Without pressure the lid will continue to spin on top of the can and the can will remain stationery. The lid and the can must be compressed together and this is accomplished with a locking lever. There are two designs for applying pressure:

Ives sealer lever pushes the chuck downward towards the lid.

All American sealer lever moves the turntable upward against the can.

The result is the same in both cases; there is pressure on a can from both ends and the whole system: the chuck, the lid, the can and the turntable starts spinning as one.

Roller Operation

The 1st and the 2nd seaming roller have different specially countered grooves. During seaming only one roller makes contact with the can. When the lid is place on a can, the rollers are away. Then the 1st roller makes a pass, but the 2nd roller is waiting its turn. The 1st roller moves away and the 2nd roller flattens the seam.

1st Roller Operation

The curl of the lid is interlocked with the flange of the lid. The first operation should not be too loose or too tight, since there is no way to correct it later.

A curl of the lid a lid is wider than the can flange and the curl starts to turn around first.

The flange of the can follows as the roller moves towards the chuck.

The lid is interlocked with the can but the can is not hermetically sealed yet. The lid might turn around on top of the can if pressed hard enough.

The 2nd Roller Operation

Second roller begins to approach the hooks

Second roller compresses interlocked hooks.

The interlocked layers of cover and can body flange are compressed, and the sealing compound is squeezed into open spaces to complete the hermetic seal.

Completed second operation.

Evaluation of the Double Seam

The shape and conformation of the finished seam are determined by the design of the seaming rolls and the taper of the chuck. Roll shapes may be changed to accommodate different thicknesses of the can material. The roll shapes, the pressure adjustments of the rolls and the base plate will determine the shape, the dimensions and the integrity of the double seam. At first sight, the shape of the double seam may appear to be satisfactory, however, one or more of the internal structures may be out of limits. As a result, a hermetic seal will not be produced. The commercial sealing machine may close 1000 cans each minute, so a defect, if not recognized soon, may result in thousands of defective closures. To prevent this from happening, a trained mechanic is continuously inspecting the production.

A Visual Inspection of closures shall be performed at sufficient intervals which may discover more obvious defects. The interval between visual inspections cannot exceed 30 minutes of continuous sealing machine operation.

In addition, regulations require Double Seam Teardown examinations which shall be performed at intervals of sufficient frequency, not to exceed 4 operating hours.

A sealer designed for home canning operates at lesser capacity, however, an understanding of the double seam inspection procedures will make a hobbyist more knowledgeable. The following drawing depicts crucial dimensions of a completed double seam. They shall be measured with a quality micrometer capable of taking measurements with an accuracy of 1/1000 of inch.

The required seam measurements: cover hook length, body hook length, width (length, height), tightness (observation for wrinkle), thickness.

The optional seam measurements: overlap (by calculation), countersink.

The question may arise as where to obtain the technical dimension of a properly formed double seam. The can manufacturer has all technical data and his distributors have access to this information.

Government regulations allow for two different types of the double seam examinations:

1. The micrometer method. The invention of the micrometer is attributed to Jean Laurent Palmer of Paris in 1848 and the micrometer caliper was introduced to the mass market by Brown & Sharpe in 1867, bringing the instrument into the average machine shop.

The seam measurements are taken in thousandths of an inch so precision tools are necessary. A standard micrometer with a round anvil may be used, however, the seam micrometer has a stem that has been specifically designed for taking seam measurements.

Closing machines produce strong double seams when properly set up and adjusted. Because there are different manufacturers of sealing machines and metal cans, it is impossible to have one set of specifications that would apply to all machines and all sizes of cans. For that reason, commercial plants obtain specifications and technical support from the representatives of the companies that manufacture the closing machines and the cans. The following seam data is offered in good faith as typical reference and not as specification or requirements: cover and body hooks each are about the same length, and they fall into the range of from 0.076 to 0.084 inches in length. These tolerance ranges are for the cans from 301 to 404 diameters. Countersink depth is around 0.125.

2. The optical method. The seam projector is a computerized accurate machine that not only displays an ex-ray-type image on the monitor, but is also capable of precisely calculating the seam measurements. Because of its cost, it is unlikely that the seam projector will be used in home canning. Commercial plants use computerized seam projectors. Quality By Vision is a global leader in the development and manufacturing of Quality and Process Control systems for the canning industry and its suppliers. Their SEAMetal HD double seam vision system provides an unprecedented look at the double seam. A sharp and clear image is supported by very precise measurements.

The system runs under Windows operating systems (including Vista) and connects to the computer using USB. The software measures: body thickness, cover thickness, seam thickness, seam length (seam height), body hook, cover hook, wrinkle (tightness), seam gap, countersink, body hook butting, cover hook butting, overlap, overlap %, (countersink - length), vee, and many more.

Teardown Examinations

In a commercial plant can must be tear-down and double seam examined at intervals not to exceed 4 hours. The examination should be also performed after a shut down. A home owner is not bound by those regulations and he is not expected to tear up the can every time he uses a can sealer. However, when he changes the chuck to accommodate a different diameter can, he must readjust the gap between both rollers and the chuck. This is a good time to tear up one can in order to be absolutely sure that the seam is tight. Comparing the closure made with a home sealer to the bottom seam made in a factory is not recommended as the two will differ. The commercial seaming heads work differently and often employ more than one set of the 1st and the 2nd rollers. In commercial operations a specially designed power-driven seam saw cuts cans fast and clean so they can be examined. A home owner will use commonly available tools such as hack saw, file or handheld rotary tools.

Teardown Procedure

Remove the center panel of the cover.

Tear off the strip of the cover left by the can opener.

Cut the can body to expose the cross section of the seam.

Examine/measure the seam.

Tools

In order to measure the seam accurately the can must be tear down.

NOTE measurements like countersink depth, seam width and thickness must be taken before the can is cut.

Can Opener. A conventional household can opener should not be used as it will distort the seam and the measurements will be off. A special can seam opener will cut the centre part of the lid without damaging the seam.

Exposing the Seam

Visual inspection of the seam is a simple procedure. Cut the center part of the lid out as described earlier. You don't need to strip away the remaining part of the lid. A home owner can use of of the following methods:

Hacksaw

File

Rotary tool with a cut off disc

Hacksaw Even if a fine blade is chosen (32 teeth per inch), cutting through the seam using a hacksaw is difficult unless the can is strongly supported. This will require a large vise or pipe holding equipment.

File The filing method presents a little problem as the cut is not perfectly clean. The metal shavings fill the gaps in the seam and obstruct the view. You will need to obtain a lath file which has one surface smooth and will not interfere with the seam. Filing is easier as one hand can hold the can and another cuts with the file.

The homeowner will probably not go much further beyond the visual inspection. To measure the body and cover hooks and to determine the tightness of the seam, the more detailed tear-down procedure is required. The body and cover hooks are compressed together but they need to be separated in order to take measurements. The complete stripping of the cover disengages the hook which is still attached to the body hook (see A).

Make two file cuts through the seam into the body of the can, about an inch apart. File through the first thickness of seam. This removes the top part of the cover hook (see B). Tap the edge of the file on the side of the filed section to knock it down and remove it. This is the hardest part, but take time in order not to damage the seam.

What follows are the most common defects that may be observed with a naked eye during tear up inspections.

Some defects are more important than others, for example a false seam or insufficient overlap may be considered critical defects. There are many more defects like sharp seams, bumped seam, droop, vee or knocked down flange.

NOTE if the seam looks in any way different than usual, throw the can away. In 3-piece cans you may compare your seam with the factory made bottom seam, however, keep in mind that it was made on a different machine. Can sealers should be checked before using to see that they are adjusted to make a good seal. One method of testing, popular among homeowners, is to partly fill a can with water. Seal the cover, then drop the can into hot water deep enough to cover the can. Use a jar lifter or another can to hold the tested can submerged. If air bubbles come up around the lid of the can, the seam is not tight and the sealer needs adjusting.

CAUTION according to experts this method will not discover microscopic size holes.

NOTE much more information about seams and their defects can be found at the excellent site

The Double Seam www.doubleseam.com

Short cover hook.

Long cover hook.

Short body hook.

Long body hook.

Insufficient overlap.

False seam.

All American Can Sealers

All American Can Sealers are heavy duty can sealers designed for use by small commercial canners, custom canners, school canneries, lunch rooms, experimental laboratories, gift packaging centers, and home canners. No skill or experience is required to perfectly seal tin cans automatically. It is unlikely that a hobbyist will need a bigger size than No. 2 can for sealing low acid products, and the 225 Master Can Sealer is well suited for the job. Larger models are more expensive and would be used by Commercial Canners, Custom Canners, School Canneries, Lunch Rooms or Experimental Laboratories. In addition, the recipes that were published by the USDA for home canning were tested for No. 2, No. 2.5 and No. 3 cans.

Established in 1909, Wisconsin Aluminum Foundry makes top quality pressure canners and can sealers under the All American® label. All American® Can Sealers include two types of sealers:

All-American Master Can Sealers to seal your choice of either No. 2 (307 x 409) or No. 3 (404 x 414) cans. Additional chucks are available for sealing other sizes, at an extra cost. The largest can size for All-American Master Can Sealers is No. 3 (quart size).

All-American Senior Can Sealers are set up to seal No. 10 & No. 12 cans, and can be adapted for smaller sizes. Those models also come in an electric version which are capable of sealing 150 cans per hour.

NOTE that 225 sealer will not seal smaller than No. 2 cans.

Ives-Way Can Sealer

Ives-way can sealer is a wonderful little sealer that has been around since November 28, 1939. This is when Clifford E. Ives has been granted patent 2.181,237 for his machine. It has had enough time to be improved upon and be perfected. Since 1973 this can sealer has been manufactured and distributed by Ives-Way Products Inc,. Round lake Beach, Illinois. The Ives-Way can sealer offers 7 different diameters and can adjust from flat tuna fish cans to the taller fruit cans. The sealer comes partially assembled with a set of different chucks and spacers. A detailed installation and operating manual is included. The company believes that it will benefit a new operator if he learns how to assemble and adjust the machine. The advantage of this approach is that by the time you assemble the sealer you will be well acquainted with its operation. You will know how to adjust the rollers, check clearances, change spacers and chucks, oil the crucial parts and always maintain it in top operating condition. Some distributors will assemble the sealer with a chuck of your choice for a small fee, however, we feel that it is best in your own interests to assemble the sealer yourself.

Chucks. By installing different chucks, the same

Ives sealer can seal cans of six different diameters.

Different models come equipped with different chucks, however, the machine remains the same. What it means is that a person familiar with the unit can purchase additional chucks and will be able to can the six most popular can sizes. Many companies distribute this sealer, but information about the machine is the best kept secret on the Internet; the reason being that until today the company has no visible presence on the Internet and prefers to do business the old fashioned way. Which, by the way works well as the company answers telephone calls and will answer any questions. Food cans come in all shapes and sizes, so one particular sealer cannot seal all of them. Sealers that are designed for home canning will seal the round cans only. All sealers can accommodate optional chucks, and that will allow to seal cans of different diameters. What follows is a brief description of the Ives-Way sealer. The sealer consists of the following parts: chuck, turntable, 1st and 2nd roller, locking lever, crank, associated hardware (pins, nuts, spacers), and adjustment wire gauges.

Keep in mind that every time a chuck is installed, both pressure rollers must be readjusted as well. Make sure you know on which side of the chuck the 1st and the 2nd roller is located. Read the operating instructions. On the Ives sealer the 1st roller is to the right of the chuck. Ives-Way sealer uses a clever window indicator which displays the stage of the sealing process the can is at.