Fully Fusing Fish in Frit

Experiments

Oct 2

Hypothesis

As an artist that prides herself on attention to detail and exactness of design, the fact that glass expands and contracts as it heats, sometimes causing entire millimeters-worth of deviation from a pattern, plagues me with many a sleepless night. Recently, while contemplating this persistent vexation, I wondered whether a solution might lie in using frit to fill the empty space around specifically-designed shapes.

Can surrounding design elements with frit prevent their expanding during a full fuse?

Sample Setup

I figured there’s no more appropriate creature to swim through a sea of frit than a fish, so I sketched a couple of finned friends to serve as the pattern for this experiment. This pattern served as the “control,” or the unchanging element that acts as a point of comparison to measure results against.

I then created two different samples (Sample A and Sample B) based off of this pattern to test whether surrounding one with frit would result in less deviation from the original size:

Sample A: two fish cut and ground to match the pattern, glued atop two layers of white opalescent glass cut to roughly the same size and shape

Two blue/gray/yellow stained glass fish on top of two layers of opalescent white stained glass — *Sample A setup, as viewed from the top*

Two blue/gray/yellow stained glass fish on top of two layers of opalescent white stained glass, viewed from an angle so as to see the vertical stack of glass layers — *Sample A setup, as viewed at an angle*

Two blue/gray/yellow stained glass fish on top of two layers of opalescent white stained glass, next to the digital pattern they're based on — *Sample A setup next to pattern*

Sample B: two fish cut and ground to match the pattern, glued atop a single layer of white opalescent glass and surrounded by a tight-fitting layer of coarse-grain clear transparent frit

Two blue/gray/yellow stained glass fish on top of a piece of opalescent white stained glass, next to a bowl of clear glass frit — *Sample B setup, pre-frit layer application*

Two blue/gray/yellow stained glass fish surrounded by clear frit, all on top of a piece of opalescent white stained glass — *Sample B setup, post-frit layer application, as viewed from the top*

Two blue/gray/yellow stained glass fish surrounded by clear frit, all on top of a piece of opalescent white stained glass, viewed at an angle — *Sample B setup, post-frit layer application, as viewed at an angle*

To create Sample B’s frit layer, I mixed coarse-grain clear transparent frit with Bullseye GlasTac Gel, using just enough adhesive to ensure each grain was coated. I then poured the sticky frit around the fish, using tweezers to manipulate it into every tiny gap surrounding the design and form it into the flattest, most cohesive layer I could.

Initial Firing

Two stained glass test samples, face-down on a primed kiln shelf, one surrounded by a metal dam — *Samples A and B within the kiln, prior to firing*

Once the glue on both samples was fully dry, I placed them on a primed kiln shelf design-sides down. Firing this way yields sharper shapes with less pattern deviation than firing design-side up.

I also dammed Sample B with fiber paper and stainless steel since I was concerned grains from the frit layer might spread outward during firing, defeating the goal of their coalescing into a single, tight-knit layer.

I fired the samples at a 90 COE full fuse schedule (heating them to around 1,500°F).

Observations

Upon removing the samples from the kiln, it was apparent the glass didn’t quite achieve a full fuse.

Sample A’s fish had a slight indent all around their perimeters, looking as if were pressed into the bottom white layers instead of sitting in-line with them.

Two stained glass fish fused into layers of white opalescent glass, with slight indents around their perimeters — *Sample A, post-initial-firing, as viewed from the top*

Fingers holding a piece of white stained glass with two fish fused into its surface, with slight indents around their perimeters — *Sample A, post-initial-firing, as viewed at an angle*

The outlines of Sample B’s individual frit grains were still fully distinguishable and the outer edge was sharply jagged. Although not fully fused, the fish designs in this sample did keep to their original shape more so than those in Sample A, which had rounded out and expanded.

Two stained glass fish surrounded by partially-melted clear frit on top of a circle of white opalescent glass — *Sample B, post-initial-firing, as viewed from the top*

Fingers holding a fused glass piece made up of two fish surrounded by partially-melted clear frit on top of a circle of white opalescent — *Sample B, post-initial-firing, as viewed at an angle*

Second Firing

Since the samples didn’t fully fuse down to the point I wanted, I placed them back in the kiln and re-fired them at a more intense full fuse schedule to melt them down further.

For the second firing, I increased both the max temperature and max temperature hold time, and left both samples undammed.

More Observations

The second firing’s hotter schedule caused both samples to full fuse successfully.

Sample A’s front and back surfaces were nearly perfectly flat, and the fish designs had expanded and rounded out in the typical manner of a full fuse.

A full fused piece of stained glass with two blue/gray/yellow fish against a white background — *Sample A, post-second-firing, as viewed from the top*

Fingers holding a full fused piece of stained glass with two blue/gray/yellow fish against a white background — *Sample A, post-second-firing, as viewed at an angle*

Fingers holding a fully fused piece of white opalescent stained glass, tilting it on its edge — *Sample A, post-second-firing, as viewed on edge*

Sample B’s frit layer had fully fused together into a flat surface, but rough outlines of individual frit grains remained visible along with numerous tiny bubbles. The fish designs did indeed hold their shape more so than in Sample A, although the seam where design meets frit had taken on a a choppy, angular look. Also, the backside surface was much more bumpy than that of Sample A.

A full fused piece of stained glass with two blue/gray/yellow fish surrounded by clear texture against a white background — *Sample B, post-second-firing, as viewed from the top*

Fingers holding a full fused piece of stained glass with two blue/gray/yellow fish surrounded by clear texture against a white background — *Sample B, post-second-firing, as viewed at an angle*

Fingers holding a full fused piece of stained glass with a layer white on top of a layer of clear, tilted on edge — *Sample B, post-second-firing, as viewed on edge*

Conclusion

My hypothesis that the sea of frit would help design elements maintain their sharp edges and stay true to pattern size turned out to be correct! However, the edges were maintained in a fairly uneven manner, and the frit layer caused too many additional undesirable impacts (choppy design element outlines and numerous bubbles) for it to be a worthwhile strategy in my opinion. However, the aesthetic resulting from this technique could be useful in a future project where such a unique look is desired.

It’s valuable to note that Sample A’s design elements expanded from the pattern size by a uniform ~1/16” around their entire perimeter.

If I assume most other 90 COE glasses fired at a full fuse will behave similarly, I can adjust for this change in future designs.

A fused glass piece depicting two fish against a white background with the original pattern cutouts of the fish on top — *Final state of Sample A as compared to the pattern*

A fused glass piece depicting two fish surrounded by clear texture against a white background with the original pattern cutouts of the fish on top — *Final state of Sample B as compared to the pattern*

A fused glass piece depicting a fish with the original fish pattern on top and a ruler showing the glass fish perimeter is 1/16" larger than the pattern perimeter — *The design element perimeters of Sample A have expanded from their original size by a uniform ~1/16”*

I’m curious as to what the results of reiterating this experiment with medium-grain, fine-grain, and even powder frit would be. I suspect the finer the frit grain, the smoother the edges of the seam where design meets frit would be, but the more tiny bubbles there would be as well…

Two fused glass pieces depicting the same two fish, with the fish in one of the pieces are surrounded by a clear texture layer, and the fish in the other being against a plain white background — *Final state of Sample A (bottom right) next to final state of Sample B (top left)*

Video Comparison of Final Fused Fish Samples

See how the final states of Samples A & B compare!

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A friendly reminder that I share details of my creation processes with the intent of empowering people with knowledge and techniques that may help them reach their full creative potential, not with the intent of enabling other artists to recreate my pieces. All of my designs are protected by copyright and are illegal to reproduce, reuse, or republish without my permission under any circumstances.

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Jackie Knowles https://www.GlassworkPixie.com