Minoan Agate Seal Ring

Front: Agate stone, shaped and polished as a cabochon, then carved intaglio-style with a Laurel wreath motif.

Reverse: brass ring and crenellated bezel setting, emulating the swiveling bezel that allows the seal stone to be worn on a finger or a chain.

Seal-stones were a common sight in the ancient world. They were used to denote rank or status, personal identity, acted as locks on vessels or signatures for received goods, or even simply as jewelry and ornamentation. John Younger, of the University of Kansas describes the use of seal stones in detail in Minoan-Mycenaean Sealstones: Understanding Chronology and Function , 2018. He details a wide variety of aspects of seal stones, from their design and construction to their breadth of function. A few noteworthy examples:

As a cultural marker:

By the sophisticated Late Bronze Age (ca. 1700-1100 BCE), the great civilizations of the eastern Mediterranean each developed its own distinctive seal shape: the scarab for Egypt, the cylinder long in use for the people of Mesopotamia, the stalk stamp for the Hittites of central Anatolia, and biconvex forms for the Aegean (the lentoid, circular in plan, and the less common amygdaloid, elliptical in plan). A seal's shape thus identified its wearer culturally."

As a security measure:

"The most commonly sealed and impressed objects are clay jar stoppers and sealings over cloth coverings of jars, doors to storerooms and cupboards, and lids to chests and baskets. The purpose of these sealings was to assist in an audit of commodities brought into the administration: the number of sealings should correlate with the number of commodities as inventoried in the documents. After the audit, the sealings would be destroyed or melted to be used again."

As personal identification:

"From the wide distribution of seals found in and about Malia, Lasithi, and east Crete, and from the (almost) complete lack of duplicated motifs, it is possible to imagine that the Malia seal engravers deliberately created unique seals conforming to the unique identities of individuals in the state of Malia....In other words, these prisms functioned as early identity cards."

A Mark for a Master

When I was asked if I would be interested in making a piece of regalia for Glaukos' elevation to the Order of the Laurel, my mind went instantly to a seal stone. As a sign that identified the user, often as a person of some sort of authority, it seemed particularly fitting to be given as an elevation gift. A symbol of the expertise, thoroughness, and attention to detail that brought him to this position and paralleled the ancient uses that valued those same virtues.

And since they were also used as maker's marks and tamper-proof lids for jars of all manner of substances, it seemed only fitting that someone who poured so much of himself into historic brews should have a way to mark them as his own.

Carnelian lentoid seal

Jasper triangular prism seal

Haematite cylinder seal

In choosing a design and shape for the seal stone, I reviewed more than a few examples from the Met of various Minoan seal stones. The variety of motifs and shapes is nearly endless, from single-sided cabochons to multifaceted prisms, to my absolute favorites: barrel-shaped cylinder seals that can be rolled across a surface to create a repeating stripe of design.

Most are made of fine-grained quartzite minerals such as carnelian, agate and jasper. These would both be beautiful, abundant, and durable stones that would take a high amount of detail and also a clean polish. Occasionally other, more extravagant materials were used; these include lapis lazuli, water-clear rock crystal, and amethyst.

"Throughout the Aegean Bronze Age seals were made of common, soft materials (2-3 on the Mohs scale), such as ivory, bone, clay, steatite, and serpentine. From ca. 1725 BCE, the Minoan palaces imported harder stones (Mohs 4-5): cornelian from the east via Mesopotamia, amethyst and rock crystal from Egypt, and a rich brown agate from an unknown source." (Younger 2018)

I chose to begin undertaking a cylinder seal, with a design of looping laurel branches, and using a really interesting blue glass material I'll discuss below.

Gravestone illustrating the Greek lapidary lathe (Methods of Engraving)

A look into methods from antiquity...

One of the most ubiquitous technologies for the cutting of fine details into stones of smaller sizes is the lapidary lathe. An extremely early example is depicted on the gravestone of a cameo cutter from second-century Greece, depicting a bow-driven rod that spun a copper cutting tool that cut with the assistance of a paste of olive oil and emery powder. This tool provided plenty of control and power to cut all manner of cameo and intaglio, from simple shapes to entire complex scenes. A more explicit description is given by John Younger:

" [Around 1825 BCE], sealstone makers were experimenting with a new tool, the horizontal bow lathe which allowed them to engrave imported hard stones (4.5-7.5 on the Mohs scale) like agate, cornelian, and amethyst.....The bow-drill employed solid drills to make dots and to model the interior surfaces of figures by passing the drill back and forth across the body. Hollow drills made circles and drilled the stringholes. A rotating wheel or pendulum saw created straight lines." (Younger 2018)

For an exemplary demonstration of the tool's function and capability, I've linked a video from the Carlos museum in Atlanta, GA, wherein Master gem-engraver Chavdar Chusev creates a replica of a Roman chromium chalcedony gemstone from the Michael C. Carlos Museum's collection of ancient gemstones, using replica ancient tools.

https://www.youtube.com/watch?app=desktop&v=Vw-DJoU3sAI

476453343_9387282434666933_3835184733594427057_n.mp4

As an exploration of this tool and cutting method, I build a concept model based on the image from the gravestone.

Two uprights, secured to a base that can be fixed to a workbench, and a set of guide rings to keep the axle from sliding too much. Using a copper roofing nail as the cutting bit, it can be driven easily by a cord wrapped around the shaft and tensioned by a bow.

Despite the optimism in my video, this replica is particularly crude and was far from refined enough to be functional on the timeline available to me. It was a interesting investigation but clearly would require mastery of several different layers of skill to be functional enough for my purposes.

Aspects of the tool to improve are:

Concentricity of the cutter and the rotating shaft
wobble/slop of the shaft back and forth
more secure mounting of the shaft in the uprights
a properly flexible bow for greater tension and less slipping

Specific skills needed to use the tool properly:

Mixing abrasive pastes to the correct consistency
loading the correct amount of abrasive on the cutter
appropriate control of rotational speed and direction
concordant motion of driving the bow and applying the cutter simultaneously
matching the right cutting tool to the geometry required by the design

...but modern timelines require modern concessions

In the interests of having this object finished before Glaukos' vigil at Pennsic, I had to make some modern concessions.

This image shows what my functionally equivalent approximation:

a plastic tote to contain spray, with a viewing hole in the top and two holes for my hands
the water drip tank from my faceting machine to supply a steady supply of lubrication and cooling
and diamond carving bits in my Foredom rotary tool for the cutting itself

Together, this represents the same set of functions as the original devices. It simply reduces a few variables like bow speed and grit application so that I can spend my time on the actual design creation portion of the process.

Eventually, I will revisit the prototype and try for a closer-to-actual-tooling cutting experience. But that will wait for when I am on less of a deadline that a vigil typically allows.

Proving the concept, testing the tools

A key part of the engraving process is matching the tooling to the design elements. Each bit shape cuts a very particular way, breaking down the design into elements that match the tooling available is essential to success.

Modern rotary tools make it easier to "cheat" this process, with high RPM and aggressive cutting capabilities allowing a novice to brute force the tool into cutting in a suboptimal way. Using a pointed tool as if it were a pencil to simply "draw" the design is a perfect example of this. The purpose of a sharp point is to make tiny adjustments to existing feature edges, or as a drill to make precise holes. When used as a scribe, the rotary motion will cause it to wander across the surface instead of drawing an exact line. This behavior is even worse on the bow-lathe version, where the slower (and alternating direction!) rotation further reduce the ability to bite into the work.

I discovered that what worked the best for drawing lines and simple curves is actually a nailhead-shaped cutter, where the longer cutting edge helps keep it aligned and stable in the cut. For long lines or shallow curves, a large diameter cutting disc was helpful. To cut shorter lines and sharper curves, a smaller disc worked better.

This experimentation was critical to my ability to reliably make the kinds of marks I needed to form my chosen designs. I did my tests on some quartz pebbles, which are of similar hardness to the common seal materials of the period and were also something I had in abundance from many trips to Midatlantic beaches. I tested the ability to make impressions using jeweler's wax, and when I had achieved a satisfactory Laurel wreath design a few times, I moved on to prepping my intended final materials.

My chunk of blue slag glass

Material and Design Selections

The bulk of seal stones I saw in the Met's online collection are agate, carnelian, jasper, and other hard, durable stones. However, I know Glaukos' fondness for Lapis Lazuli, and I had seen examples of seals cut from that as well.

I didn't have any good pieces of Lapis of the right size or shape, but I did have this beautiful blue slag glass. "Slag" is scrap material left over after manufacturing colored glass items. This particular piece was intended to be made into sheets for stained glass and mosaics. Note the bubbles and metallic inclusions that would have made it difficult to use for the intended purposes.

It conveys a lot of the same visual beauty, and I had enough of it to experiment several times if necessary. It also calls to mind the blue Egyptian glass called "faiance" which, while I haven't specifically seen a faiance seal stone, was a common stone for all sorts of jewelry.

I sliced the slag into a few different blanks, intending to attempt a cylinder seal. I found those the most interesting, and loved the idea of creating a repeating "ribbon" of pattern.

The process: Preparing the seal blanks and design layout

Using a diamond bit to drill the hole that will be the cross bore of the finished seal, and also to provide a strong contact point for mounting on a dop stick

Using a diamond lapidary saw, I trim away the excess glass to make forming the cylindrical shape more efficient

Using my faceting machine for stability, I roll the seal blank on the spinning lap to form a uniform cylinder shape

The seal blank, now at final dimensions, ready to begin the design and carving process

I wrapped a piece of paper around the blank to get the size, and then made the oscillating shape that I want to use as a vinework pattern

Using a sharpie, I colored around the template to transfer the curve to the stone

Using a nailhead carving bit, I carefully cut a channel along the edge of the previous mark. As I make each cut, I go over the piece in sharpie. This increases contrast and makes it easier for me to see where and how deep I've already cut in each step

As I kept cutting, I used a strip of polymer clay to check what the impression looked like and verify that my depth of cut was correct. This is the complete laurel-leaf border, and at this point the blank is ready for the central charges

Lace Agate cabochons I cut at Patuxent Lapidary Guild

Alas, it was not meant to be.

Unfortunately, every single attempt to create a seal blank out of the slag glass was a failure. I was never able to get farther than the previous two images without a mistake or misfortune that ruined the seal blank. Whether it was from the tool unexpectedly binding and digging in, to the blanks shattering with various degrees of drama, none were successful. I suspect that the scrap-material nature of the glass is to blame; inclusions of bubbles and metal particles, uneven density, residual stresses, and more all could contribute.

I was forced to abandon the cylinder-seal concept and switched to a cabochon shape with the engraving to be done on the flat back side. Fortunately, I had two excellent examples of lace agate I had cabbed the prior year and never found a use for. This was the perfect occasion to show off the gorgeous banded colors that had drawn my eye in the first place.

Since seals were nearly always designed to be specifically reflective of the bearer, I wanted to include a reference to at least one of Glaukos' many specialties. Originally this was going to be done as the repeating motif in the center of the cylinder seal, with the laurel continuous around the edge.

Using a cabochon required separating the symbols across two seals. And since few indeed are the folk who do not immediately associate Glaukos with an amphora full of excellent wine, the motif of the second seal was a simple one.

Fortunately, it's also composed of simple shapes that I had tools to match. With a flame-shaped cutter for the body and neck of the vessel, and a disc cutter to draw the handles, it came together with no issues.

Most importantly, both cabochons held up to the engraving process well. This is unsurprising, given the vast number of agate seals from this period.

Surface cleanup with a lapping plate

In order to bring the seals to a better surface finish (and to clean up any errant cutter marks) I used a lapping plate. These are the simplest way of cutting stones, using simply an abrasive and hand action to shape and polish. Originally done on sandstone blocks, it was discovered that using abrasives like Naxos stone on metal plates was faster and more effective.

"Naxos Stone" as referred to by Pliny and Theophrastus, is a particularly high purity and fine grained mineral called corundum, or Aluminum Oxide. It's also known as emery powder, and the fine grains and high hardness make it an excellent cutting and polishing abrasive. I am using synthetic alumina, made for rock tumblers, as a more consistent source of the same mineral. Making a paste of this with some mineral oil (to avoid the risk of the traditional olive oil going rancid) and rubbing the stone against the plate is a surprisingly efficient method of shaping and smoothing the edges and face of the carved seals.

The original surface finish on a test piece of agate, as left by the trim saw blade

Cleaned surface after a few minutes of treatment on the copper plate

Diagram from "Jewelry Technology in the Ancient and Medieval World", Jack Odgen

finger-ring; scarab | British Museum

Findings and Hardware

Originally, the plan was to mount the cylinder seal on a cord for easy use and convenient carrying. This had to be modified for the cabochon seals.

Seals carved with scarab likenesses on the domed side were frequently mounted in a swiveling setting that allowed wearing as a scarab ring, then flipping to be used as a seal with a handle.

Unfortunately, this does require the drilling of a thru-hole that I didn't have the space in the stone to add. I settled on a hinged approximation that preserves the intention of the mechanism, and for the seal to be easily carried on a chain. All fabrication was done from jeweler's brass, with a crenellated bezel and a hinged ring shank.

The completed items

For presentation at Pennsic, I assembled a small gift box with "previews" of the seal impressions in polymer clay dyed to resemble terra cotta. The Amphora seal was left unset to be used however Glaukos saw fit. The Laurel seal was presented on a chain provided by Ollam Lanea, who also provided transportation of the item when I could not attend the elevation myself.

In the end, it was a rewarding project that exposed me to a new facet of the lapidary arts and has since served as a springboard for me to spend more time investigating and experimenting with the lapidary lathe concept. The mechanism remains surprisingly constant through the entire rest of the SCA period, with mostly the changes coming only from improved hardware and efficiency gains.

But that's a project for another time.

In the meantime, it was an honor to be able to produce a piece for such a spectacular researcher, artisan, and friend as Glaukos.

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