Test Cabochons and More


This full fuse firing was all about testing a few ideas to make glass cabochons for jewellery. You will notice in the ‘Before’ photo that the items are placed on separate pieces of BullsEye Thinfire kiln shelf paper. For no specific reason other than to use up the paper offcuts.

All glass is BullsEye COE 90. Most glass is 3mm, but there were a few 2mm pieces in some stacks. Everything was fired to a full fuse. The Firing Schedule I used is shown below.

Before Firing

On the top piece you can see two thin test pieces on the left. These are black with iridised clear on top. On one piece the iridised surface is down, on the other it is up.

Cabochons Before Firing
Cabochons Before Firing

In the middle top is a broken piece from a puddle and below that a large test item of two clear pieces with 2mm thin pieces in the middle.

On the right are three cabochons from a previous full fuse that had devitrified. I have ground of the devitrification and was testing to see if I could save the pieces.

On the bottom piece of paper on the left is a test for the inclusion of a bail made from fine silver wire. This is not sterling silver as sterling will blacken in the kiln. You must use fine silver wire.

To the right of that is a test of pieces placed side-by-side to see how they fused, and below that is a stack of offcuts without fibre paper.

One idea I really wanted to try was inserting fibre paper into cabochons to make a channel for threading wire, thread or any suitable material. In the middle you will see five cabochons made from stacked offcuts. Through these we placed small strips of 2mm fibre paper. We selected darker colours for the top pieces to hide any wire or thread.

To the right of these are several small squares of clear and black glass to test making simple round dots for use in other projects.

After Firing

Cabochons After Firing
Cabochons After Firing

The ‘iridised’ glass test showed that firing with the iridised surface up (piece on the left) resulted in a metallic sheen to the glass, but with it down gave a deeper iridised effect within the glass.

The chip from a puddle fused down well but again there was a little devitrification. The devitrified pieces that I tried to rescue did not work. They still retained some devitrification. It seems that the orange glass is prone to devitrification.

The inclusion of the fine silver bail worked fine, but note the discolouration to the shelf paper and shelf itself. I am not sure what has happened here and will do so research. Otherwise, the piece is fine.

All the fibre paper tests worked well, leaving a clear channel through the cabochons. The channel did need to be cleaned up a bit as there were some sharp edges.

The clear and black dots all worked fine, though a couple did not quite form into perfect circles.

All in all, the firing was a success as far as the test and I did learn a great deal, though it did raise more questions.

Firing Schedule

SegmentRate (C/hr)Target (C)Hold (mns)
1. Ramp Up54053810
2. TargetFULL7885
3. AnnealFULL51660
4. Cool1803715

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