Skip to main content

Virtual Kingdom A&S 2020: Chalcedony/Striking Glass

After my last project which was focused on just successfully making a glass, I began trying to refine my batch composition to eliminate lead so I would be comfortable using it in projects that do not stay with me. Shortly after accomplishing this, I got distracted by the range of effects that can be produced by including silver in glass. One effect I focused on is called striking, which is where the glass shifts through a rainbow of colors when reheated.

I approached this under the impression that striking glass was a more recent creation, but in the middle of the project, I came across extant pieces with similar coloration that were referred to as chalcedony glass. I eventually found a recipe dated to 1443 for this glass, and it did include striking as the last step of the process. This recipe, however, called for mercury and lead in its components. I had just managed to get lead out of my batch, and I was definitely not going to introduce mercury, so this project focused more on comparing the materials and final results than directly recreating the historical glass.

To use striking glass, it goes through a process of resetting, cooling, then striking. The glass is reset by getting it hot enough that the silver crystals which currently exist are dissolved into the glass and it turns transparent. Next, the glass is cooled, either by just removing it from the flame, using a marver, or if making vessels, blowing the bubble. When it cools, some of the silver is reduced out of the structure of the glass and forms particles of metal throughout. Finally, when it is reheated to strike, those silver particles serve as nucleation sites for the silver still dissolved in the glass and they begin to grow. The smallest crystals produce a yellow color. As they grow, the color shifts to an amber, then through purple, blue, green, and finally tan. If the color strikes more than desired, the whole process can be repeated by resetting the glass again.

The beads seen here are an assortment from all the batches of glass I made, with the most recent in the bottom row. Some of them have a core of commercial black or white glass to lower the amount of special glass used per bead.

    The bottles are all from my last batch of glass, although the three on the left have had commercial white glass blended in to try to enhance the banding. The fourth bottle is all striking glass and has some variegation visible still, although it is less pronounced than the historical examples. This is likely because I blended all my batch ingredients together then melted them, instead of melting the base glass then blending in the metals later like the period instructions call for. You can see the effect that rate of cooling has on the final colors by how the beads take on a rainbow of colors while the bottles stay more on the amber side of the scale.

    Here is the documentation submitted with the project, which goes more into the composition of the glass.


Popular posts from this blog

Making Metal Purple: Enamel and Patinas

One problem I ran into with my award medallion project is how to make metal purple. Because Calontir likes purple. A lot. After digging around, I came up with four possible plans: Enamel Patina Dye-oxide Dyed epoxy Enamel This was my first choice, as it both looks pretty and fits into the time period of the SCA. After some modifications to my soldering station and a promising test on scrap copper, I took one of my newly cast Golden Swan medallions and went to work. A layer of enamel was applied and things looked good. The medallion was set aside to cool. While I was cleaning up other parts of the shop, I started hearing a faint little "Ting! Ting!" coming from the soldering tray. All of the beautiful enamel was popping off! Which lead to the first lesson from this project: coefficient of thermal expansion. I broke off some of the surviving enamel to be able to test other things, like some purple paste wax in the upper right. But you get the idea with the broke

Fox Masquerade Mask

I've had the idea of making a metal fox mask for a few years now, but haven't really had a reason to do it until this year. Work decided our holiday party would be a murder mystery masquerade, which makes a great excuse. The basis for the mask was Wintercroft's Fox Half Mask . The half mask is perfect for the masquerade use, and I thought the papercraft/low poly look would translate well to the metal. I took the mask template and glued it to 22 gauge copper sheet with spray adhesive. Then after about an hour of work with a jeweler's saw... I had the pieces, somewhat resembling a fox mask, but mostly a Batman logo. The paper templates were attached to the other side, so I could use the dotted lines for initial bends. These were mostly done on the corner of an anvil or over a piece of 1"x4" clamped in a bench vice. A rubber mallet was used instead of a metal hammer, since the rubber won't leave indentions in the surface where the hammer str

Konstantia's Coronet

At Fall Crown Tourney, Konstantia was made a baron of TRM Damien and Issabell's court. I had the pleasure of making her coronet. I also managed to not spend the last three months with my fingers steepled while cackling maniacally. Design There was a moment of worry at the start of this because I said I would be interested in doing a coronet before I knew who it was for. When I heard it was for Konstantia, I knew that meant Byzantine. Which means bling. Lots of bling. I had actually made a comment to Jakob before about Byzantine style looking like a pain to make because of the amount of bling. But, it was a good challenge. My initial research into styling for a Byzantine coronet turned up two basic design concepts I worked off of (citation needed, since it appears I didn't save these sources): Stones were more important than the gold. The Byzantine empire was full of gold mines, while precious stones were imported. So, the focus was on the stonework while the metal i