Late Anglo-Saxon Disk-Brooches. Part 3 (Enamel)

Fig 1.The first four colors of Flameworking glass rods that I
processed into fine powder to use as vitreous enamel.
Next to each plastic container is a piece of the
glass rods that I used as a source for the glass.

This is Part 3 of my series of blog posts about my Late Anglo-Saxon Disk-Brooch Project. Please see Part 2 of my blog post series for information on my reasons for experimenting with Flameworking glass rods and turning them into a fine powder which can be used as Enamel.

Part 1 is a general history of the disk-brooches that my research and fabrication project centers around.

At the start I used Propane fuel with a standard plumbing torch head to heat up the glass rods (Fig 2). My sheet of Stainless Steel was on top of the table with the mortar on one end next to the sheet. 

Fig 2. Left over fragments from
3 Flameworking glass rods.

The mortar was filled with ice water, this is where the heated glass will fall and shatter due to the thermo shock (Fig 3 & 4). The temperature change between being heated up and the ice water will over stress the glass and cause it to break into tiny shards due to the sudden cooling effect. The ice water also containing the pieces within the water and prevents them from flying about.

Fig 3. Once I switched from using Benzomatic's
Propane fuel and a basic torch head
their MAP-Pro and Hot Head torch .

I started with the red opaque glass rods. I held a length about 2 to 2 1/2 inches in a pair of long handled pliers and heated up as much exposed glass without getting the pliers in the flame. I didn't reach molten temperatures before I dropped the full length of rod into the cold water. It shattered a bit, but not as much as I had hoped. I continued with this method until I had enough shattered pieces in my mortar.

Fig 4. A close up.

I moved on to the next series of steps, crushing and grinding. I spent 10 to 30 minutes crushing and grinding the pieces with the pestle against the inner curve of the mortar. Every time that the water becomes very cloudy I rinse away the 'fine' or 'fines', very fine particles that float and cloud up the enamel's look, and added fresh water before grinding some more (Fig 5). 

Fig 5. The tilted mortar exposes the hidden
ground particles. More grinding is needed.

After the final rinse  (Fig 6) I spread the paste onto heavy duty aluminum foil for them to dry in the toaster oven, set at a low heat (Fig 7). Once cool I placed the contents of the mortar in a plastic 40-Mesh Enamel sifter and sifted it into a small bowl with the aid of a brush to move the particles around. When it stopped separating (Fig 8) I poured the fine particles, that the sifter removed, into a plastic storage container with a tight fitted lid. This is ready to be used as Vitreous Enamel.

Fig 6. Ground and rinsed a few 
times, this is ready to dry.

I placed the particles that stayed in the strainer back into the mortar, added some water and continue grinding, rinsing, drying, sifting until I was satisfied with how much I was able to grind fine enough for enameling. Then I moved to the next color and so on.

Fig 7. The paste is spread onto heavy
duty aluminum foil, dried in a
toaster oven at a low heat until dry.

Once I switched to the blue glass I decided to try heating the glass rods with MAP-Pro and switched to the Hot Head torch head, this heat source gave better results. 

At the same time I stopped trying to heat as much of the rod as I could in one go and decided to bring the last inch of glass to a molten stage and create a large drop shape. I continuously rotated each glass rod while heating it until it became molten. By slowly twisting and turning the rod in the flame I created a large teardrop shape which shattered in the ice water once it detaches from the rod. 

Fig 8. Sieving the dried glass through a 40-mesh
screening. The particles in the mortar are
smaller than the ones that are still in the sieve.

The extreme temperature difference between being molten and then hitting the ice water, with the added ice cubes, caused a greater thermo shock with more breakage. Success!

Once I have enough length of the glass rod shattered I remove the ice and some of the ice water. I continued with the above method of grinding, rinsing, drying, sifting, storing particles for all my lengths of glass.

Fig 9. Top row: Particles smaller than 40-mesh.
Bottom row: Particles larger than 40-mesh.
Left: Opaque red glass.
Right: Translucent dark blue glass.

Due to time constraints and the wear & tear on my hands and shoulders I spent 2 1/2 days processing the glass rods into 80-mesh enamel particles. With that in mind I didn't completely crush all of the glass that fine, I kept some larger particles for future comparison and to also work on some of it in the future when time permits. 

The Sterling Silver Bezel cups that I have are about the size of the ones on the brooches lobes and I have more than enough ground enamel for test samples as well for making one brooch for display.


Suggested Tools and Supplies

• Flameworking glass rods in several colors all in the same Coefficient of Expansion (CoE), these are usually used to make glass beads. I used CoE 104 Opaque glass rods.
• Benzomatic's Propane fuel, it burns at 3,600 degrees Fahrenheit.
• A standard plumbing torch head
• Benzomatic's MAP-Pro fuel, it burns at 3,730 degrees Fahrenheit
• A Hot Head torch head.
• A lighter.
• Safety Glasses
• A pair of long handled Pliers or glass rod holder.
• A none burning work surface like a large cookie baking sheet, piece of Stainless Steel, etc. (as seen in Fig 3)
• Granite or Agate Mortar and Pestle set (as seen in Fig 3 & 8).
• Ice and cold water.
• A 'Plastic 40-Mesh Enamel Sifter with Handle'. Item # 119305 at RioGrande.com (as seen in Fig 8)
• Several small bowls or white paper, Fluted Baking Cup for cupcake/muffins. To temporarily store dry, crushed glass.
• Aluminum foil or Aluminum pie plates.
• A funnel or a sheet of paper folded into a funnel.
• A paint brush for Art oil painting or a soft 'dollar store' paint kit brush. An old toothbrush would work as well.
• Several small, plastic storage containers with lids or old pill bottles that have been cleaned and dried (as seen in Fig 9).

Please NOTE: A 14.1 oz tank of MAP-Pro fuel is about 3 to 4 times the cost of a 14.1 oz tank of Propane, but MAP-Pro gas will heat the glass faster and to a higher temperature than Propane especially with the different torch head which is designed for Flameworking, melting glass. If you do not already have a 'Hot Head' torch head or a similar Flameworking torch head then use a plumbing set of tank and torch. It will take a bit longer to heat up the glass. An oven does not reach the needed temperatures to melt glass.


Part 4 of my series of blog posts will be about the results of firing the Enamels I made. I will not be mixing my Enamel with my Thompson Enamel powders due to the different CoE which could cause issues.