Fusing with Natural Mica

Recently Elaine F. from Idaho generously mailed me some of her mica stash to try. I’ve wanted to use natural mica before, but haven’t had the opportunity. Mica is the name for a group of sheet silicate minerals. They are distinctive for the flat thin sheets that can be flaked apart. They are typically translucent to transparent, although there are different hues from silver to copper.

The samples that Elaine sent me are more in the dark silver color range.

The first thing I did was fuse some small pieces between layers of glass.

I noticed that the mica turned more gold, and was probably off gassing to create the large bubbles.  The next step is to try heat treating the mica by itself to see if that could solve the bubble problem by burning off any organic material.

Heating pieces was simple, I put the sample pieces in small terra-cotta saucers and just slipped them into the kiln with a batch of other things.  I fired samples with my ceramics, and with a batch of fused glass.  The results are quite interesting.

You can see that the mica became more copper colored as it was heated to a higher temperature.  The next step was to do another fusing test to determine if the color change is permanent, and if the bubble creation problem is resolved.

Although the mica pieces captured air, similar to any inclusion, there aren’t any large bubbles.  Here are detail photos for contrast:

The copper color remained during glass fusing.  It appears that the color change is permanent.  I also found that the mica is much more fragile and can easily be crumbled up after being heated.  It is also easy to separate the sheets with a razor blade before or after heat treatment.