Glaze Studio and Glazes

Glaze Studio

The work area is a small bar sink in a vanity cabinet. I have not installed a clay trap for the drain but use a waste water bucket when I am cleaning up. 

Ideas and Hacks

1. Glazed and kiln ready storage area consists of two shelves lined with shelf paper or heavy paper.

2. Ware boards help move pieces to the kiln. A full kiln is about 5  full boards. 

3. The sink area is protected with a sunflower bird seed bag for easy clean up.

4. My glaze buckets are 1.25 gallon buckets with lids from Truevalue hardware found in paint section. I tried ice cream buckets but found them flimsy and 3 and 5 gallon buckets are too large for the space. 

5. I use plastic grating from a dead box fan and "White Egg Crate Styrene Lighting Panel" from Home Depot to set wet glazed pots for drying. 

6. Glazing tools are cleaned in a 1 gallon plastic ice cream container container then waste water added to a glaze waster water bucket.

7. The glaze waste water bucket allowed to settle and water siphoned with glaze sludge added to recycled glaze bucket. Recycled glaze used to glaze pots.   Colors form recycled glaze are uniquely green brown mix.

8. Wet carpet makes a good rub pad for rubbing glaze from bottom of pots or areas that will set on kiln shelf. Rub pad should be larger than 6 by 6 inches. Write the color of the glaze on the back padding and use it only for one color. Carpet is rinsed and hung to dry between use. 

9. Make a simple siphon from 1/4 inch drip irrigation tubing for removing water once glaze has settled out. Siphon is 1/4 inch drip irrigation tubing with a double 90 degree connector to make a u shaped dipping tube for bucket. Dipping tube should extended to within 1.5 inches of bottom bucket. Use a large syringe to start the siphon into a 3 gallon waste bucket. I use water from waste bucket to water my flower bed.  Annually, rinse the siphon using a garden hose to clean it out.   

10. A small oscillating fan hung over the glazing area helps dry the glaze. 

Glaze terminology

Glaze Components 

1. Glass formers make the glaze. 

2. Fluxes reduce melting points of the glass formers to a level where the kiln will melt them to make glass.  

3. Stabilizers prevent glaze from running off piece

4. Suspension aids keep mixture in suspension between use

5. Colorants add colors to glaze

Table:  Glaze Components

Name                                                 Flux                    Glass Former            Stabilizer              Suspension aid  

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Ash (Wood Soda)                           XX

Borates                                              XX

Clay                                                                                        XX                             XX                           XX

Dolomite                                          XX

Feldspar                                           XX                             XX                             XX

Nepheline syenite                        XX                             XX                             XX

Silica                                                   XX                          

Spodumene                                     XX                             XX                             XX 

Talc                                                     XX

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Basic glaze

I know I do not follow traditional glazing techniques or methods because I fire glazes at cone 10 and fire a mix of bisque and glaze pieces in the the same kiln. In part it was to accommodate Wendt's clay and because sometimes there are not a full kiln ready for firing. I also realize in an electric kiln the colors from the glaze will not be the same as reduction firing with gas or wood. Being a beginner and not trained as a potter, I do not mind the strange color outcome. I am just happy to see the piece did not explode, melt, crack or bubble in the kiln. Glazes with copper or reduced iron are interesting to me but would be considered to be a failure by professional using a gas or wood fired kilns. 

Initially, my glazes were Cone 10 Laguna and mixed in 5 lbs batches. A 5 lb batch makes 2 quarts glaze. After a year, I order in 20 lb bags to reduce costs of material and saved handling charges when I ordered a large shipment of raw components for making clay. In the spring of 2019, I found cheaper shipping for clay components from a source, but they did not sell Laguna Glazes. It was time to mix my own glaze from raw materials. I started with a basic search of Cone 10 Glaze Recipes and found lots of them. 

Glaze recipes are confusing with a variety of components and weight units. For example I found 8 kinds of kaolin, and 6 types of feldspar. Weight units were listed as %, grams, pounds, and undefined units with large numbers. It was spreadsheet time where components could be listed and weights standardized to a ratio expressed as % and a weight to yield a 4 lb batch. 

In reading through recipes, I decided all my glazes should be a suspension and not have water soluble components and they were not to have a toxic or lead component. Digitalfire.com suggested find a base recipe and change color components would be a good place to start. 

In 2025,  I changed ingredients to reduce bubbling and replace bentonite with Om4 ball clay.  The firing temperature was lowered to cone 9 in preparation for the shift away from Custer feldspar.  Custer feldspar is no longer available.  

My 2025 basic glaze is a Tenmoku or Temmoku with mineral color clay added. 

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Ingredients (function)                   Wt (lbs)

Om4 ball clay (suspends)                    0.4

Feldspar, Custer (^melting temp)   1.74

Flint silica (glass former)                  0.97

Kaolin clay (suspends)                       0.39

Whiting (flux)                                        0.50

Color weight range from 0.05 to 0.3 lbs depending on desired color. 

Add to two quarts water and stir after each ingredient has been added. Two quarts fits in a True Value 1.25 gallon bucket with lid.

Screen glaze mix into a fresh bucket using #60 mesh coffee can sieve. Let settle 2 days and siphon off extra water from the top of glaze. Makes about 1.75 quarts of glaze.

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For Matt Tenmoku glaze replace whiting with dolomite.  

Ash glaze

A wood fired kiln generates amazing flowing textures and colors when the ash is melted on the outside of the pottery. It is really why I want to build a wood fired Kiln. Simon Leach sprays wood ash on his pottery to produce the wood kiln look. The idea was interesting, but I found spraying to be messy. My alternative was to dip or paint on the ash.

Processing ash

1. Obtain ash. My ash came from Robert Carver's fire place and mainly paper ash. Ash may be from hardwood, softwood, rice hulls, or wheat straw fires. 

2. Screen ash using window screen. Need about 5 lbs screened ash (1 quart in volume).

3. Mix screened ash to 2 quarts water in a bucket. Use drill mixer to mix. 

4. Let set overnight before using. Mix well before and during dipping or painting.

5. Let dry. Super clean bottoms of pot and 1/2 to 1 inch up sides. Wood ash glaze loves to run.

Granite glaze

Granite counter top cutting and grinding sludge was obtained from Granite Concepts of Lewiston, Idaho.  They indicated it was a mix of granite and hardboard cutting sludge and  garnet grinding and polishing sludge.  They were happy to give me a 3 gallon bucket full.  Sludge was dried and stored.  I probably have a life time supply if used only for glaze.

I used the dry granite sludge as a feldspar replacement in my basic Tenmoku glaze. The glaze was sieved with a 60+ mesh.  The fine mesh caught a few larger garnet about 30 mesh in size.   

Ideas and Hacks

1. Keep a log of results. Do not be afraid to throw bad glazes into the recycle bucket.  

2. Some pots have bottoms dipped in hot wax to prevent glazing. Candle wax is melted in a 9x13 cake pan on an electric griddle set at 240 degrees F. The wax depth is 1/4-3/8" in the pan.  Some larger pieces will not fit in a cake pan so I am looking for an alternative.  

3. I use plastic soup serving ladles from Dollar Tree for a stirring and pouring glazes. 

4. Glazes are stored in 1.25 gallon plastic paint buckets from TrueValue Hardware. I tried 5 quart ice cream containers but found them flimsy.

5. Stir between dips.

6. Utensils used for glazing are rinsed in a small container and rinsate saved in a waste glaze bucket. Waste glaze bucket allowed to settle overnight and siphoned using siphon tube described above.

7. Let glazed pot dry overnight before handling for clean up and checking to see if a second coat of glaze is necessary. 

8. Bottoms of dried glazed pots or areas expected to touch kiln drip chip are rubbed on a piece of damp carpet. After pot rubbing the carpet is rinsed with rinsate caught and disposed of in waste water bucket. 

9. Fired glaze can have sharp edges. I use a handheld rotary grinder with small ceramic rated grinding wheel to remove the sharp bumps of glaze. Grind near dust collection fan. 

10. A coffee can sieve is used to strain glaze. The #30 mesh or 600 micron paint strainer is made by Trimaco and purchased at True Value Hardware. The #60+ mesh is Organza (wedding vale). Organza is often sold as Wedding decorations. I purchased in 54 inch by 10 yard quantities for about $10 ( lifetime of filters). Remove bottom of can and cut large hole in lid. The best can opener for doing this is a Swiss Army knife with a can opener. Attach mesh to bottom of can with lid then duct tape extra fabric to side of can for extra hold. Thin the glaze 125% and stir glaze in sieve with a wood paint stirring stick while pouring glaze. Many potters use commercial #60, 80,100 mesh sieves but pricey. Total cost to make several coffee can strainers was less than $1.00.

11. Screen glaze if you add anything.   Screen to refresh settled glaze and screen often.  

12. A paint stirrer for electric drill makes a great glaze stirrer. Works with and without drill. 

13. Double dipping rims after first dip has dried. Changing colors has cool effects. 

Glaze problems and workarounds

Originally I titled this sections Glaze problems and solutions but I have not found solutions just workarounds.  Sometimes it is just good to start over or never try that again.  Glazing it the most iffy step to making pottery.  

I use the glaze termed as a suspension meaning it is not dissolved in water but remains as partials suspended in water.  This presents challenges and opportunities to adjust the  thickness of the glaze and keep it evenly distributed in the glaze bucket.  There are a bunch of jargon terms for glaze problems but I will leave them in the class room.  

Problem

1. Glaze settles between use.  

   1. Use an electric drill paint stirrer to remix 

   2. If it settles again add 2 tablespoons bentonite, 1 quart warm water, mix again and screen.  Let set overnight and siphon off extra water.  Stir in 1 quart warm water and let set overnight and siphon off extra water.  The glaze should be ready to use.

   3. If you hate the settling problem use/mix the glaze more often or remove it from the glaze room. 

2. 
   

Grinding pot and mug bottoms

The use of kiln chips often leaves rough spots and shards of the chip in the bottoms of the wares.  After cutting my fingers multiple times on something sharp on the bottom of the pot I have started to sand as I take the pots out of the kiln.  Seem to make sense all pots regardless of bisque fire or glaze fire are sanded while I have on the kiln gloves.   First sanding is with  100 grit paper and three strokes across paper then repeated with 150 grit paper. The paper is held on a flat piece of metal with the hand not holding the pot.  

If further inspection with a hand lens shows additional shards missed by sanding then a Dremel tool is used to remove them.  

In July 2019, a Wen 8 inch grinder was added to my studio for grinding large glaze drips.  

Other methods used to smooth pot bottoms.

1. I saw Simon Leach rub bottoms of pots with another pot to smooth the bottom.  I used this technique for a few months but found it chipped the edge of the trimmed bottoms.  

2. Dremel tool and bench grinders with a ceramic grinding wheel as a way to smooth pot bottoms.  The Dremel tool works for big rough spots and shards but the pot still feels rough like fine sand paper. 

3. A rubbing board ( 12 by 13 inch ceramic slab with canvas texture) but it failed to get all rough spots.  I have glued 160 and 220 grit sandpaper to foam shelf liner foam.  The sandpaper  is used to buff any rough spots missed by the Dremel tool.  

Thoughts and Hacks

1. A word about Dremel tools.  I purchased a cordless Dremel model 1800 on January 25, 2017.  It died May 28, 2019 a few months out of warranty.  Bought a second one and hoping it last longer.  Battery of old one works in new.  Sounds like the bearings were going out on old unit based on the sound of the new one.  That is what happens when you grind pottery.  

2. A magnifying glass on a stand has proven to be useful in finding where the pot may have some kiln chip material and uneven spots.  It is also great for detecting any flaws in the glaze.  I purchased the Helping Hands Magnifying glass from Harbor Freight for $5.  The glass is large enough it also acts as a safety shield when grinding.   They have a lighted Helping Hands unit with high magnification for $8.  

3. The Wen 8 inch grinder vibrated a lot when first tested.  Solved vibration by loosening wheels and rotating wheel 180 degrees on shaft.  Still have a side to side movement in wheel but vibration gone.  

Roller Ball Mill

A mill is used to grind materials to small particles. The concept is a milling jar with balls rotating to crush and grind the material. Most potters never use a roller ball mill because materials needed for making pots and glaze can be purchased as a fine powder. The only time where a roller ball mill comes in to play is when you have collected raw material for glazes. Commercial mills are available but expensive (+$1,000). I decided to adapt a design from digitalfire.com for $300 including jar and 60 grinding balls. Websites indicate a 5 quart mill jar needs 50 to 150 - 1 inch grinding balls for best grind. Shimpo has a sales flyer that covers rpm and number of grinding balls for different sized jars. There are also formulas for estimating optimum RPM for best grind.  Note: the results from web published formulas for calculating optimal speed for grinding did not match recommend Shimpo speeds.  More testing is required for batch size, optimum RPM and grinding times. 

Shimpo roller ball speed chart

1-Liter 64.0 rpm

2-Liter 53.4 rpm

3-Liter 45.7 rpm

5-Liter 40.0 rpm (my jar size)

10-Liter 32.0 rpm

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The base of the mill is 3/4 inch plywood. Conveyor rollers (2.5 by 22 inch) and end brackets were from Zoro.com ($114). The conveyor rollers have bearings on either ends. Grinding jar aligned with 1.75" o-rings placed on conveyor rollers to match groove spacing on grinding jar. O-rings help keep jar off metal roller. ($4) 

Mounts for conveyor brackets and end rollers were made from 1x2 inch plastic fake wood trim cut 9 - 12 inches long. Rubber casters were added to the ends in the event the jar moves off the o-rings ($6). Casters optional given plastic wood used for end mounts.

The grinding jar is a 5 quart ceramic jar designed for grinding. Jar and 60 one-inch grinding balls was $162 including shipping (Axner.com). Additional grinding balls were made with the porcelain clay body I use for throwing.  A variety of sizes (0.5 to 1.5 inches) were made and fired.   The size of grinding balls appears to be a factor in fine grinds. Still testing to see if including 1/2 and 1.5 inch grinding balls helps. 

Motor 

The motor has proven to be the challenge.  The prototype used a 12 volt drill (900 rpm) modified to power from 12 volt solar system with a 3/8 bolt for a pulley and vacuum cleaner belt.  The roller ball mill did not produce the results expected in 2018 because of the motor froze and the belt kept coming off.  

Second try.  The mill sat idle unto 2020 when I changed the drive motor to a Greartisan DC 12V Turbo Worm Geared Motor ($16).  It is a 6mm shaft motor with the fix speed of 250 RPM.  I tried a 25 RPM motor but found it too slow.   The 250 RPM motor produced a drum speed of 30 rpm, but after 3 minutes of operation smoke came from the motor and it froze.  So back to calculating torque because the small high torque motor was not that high torque.   

Third try.  A sewing machine motor with foot control for variable speed was tried.   The foot controller was replaced with a light dimmer so a constant speed could be achieved.  A  motor speed of 500 to 600 rpm powering the mill to turn at a rate of 80 rpm.  I used the sewing machine belt that came with the motor to drive the mill.  I tried a 1/4 inch o-ring for a belt but it popped off.  I have ran for a 20 minute test and hope to conduct further tests with material in roller jar.  There is some variability in speed even with the dimmer switch.  Attributing variability to low horse power of motor when running at low speeds and may need to invest in a geared reduction transmission.  Hum wonder of the sewing machine motor will work for the pottery wheel I am building.  

Forth try. Variability in speed of the sewing machine motor became a problem.   I ordered a Uxcell High Torque DC 12V 160RPM Reversible Electric Gear Motor 80W 3N.M  and a 58mm OD 10mm Bore V Groove 1 Step Pulley for Belt 3/8".   The 3N.M. converts to 27 lbs per inch.  A speed of 160 rpm with 5.8 cm OD pulley should rotate the ball mill at 42 rpm or 2579 rphr.  

New Uxcell High Torque attached using a 6 inch diameter 1/4 inch o-ring (O-ringdepot.com).  Rotational speed is 40 rpm or 2400 rph.   The motor and gear box stayed cool to the touch after a 30 minute test load test. 

In the fall of 2023, I started to have problems mixing the dry clay mix by shaking the 5 gallon bucket.  My solution was to use the roller mill to motorize the mixing process.  I modified a 5 gallon bucket with a pair 1 by 2 paddles to aid the mixing process.  When the bucket is added to the mill it slips so supplemental hand turning is required.