Quick Tip: Powder Power | Kilnforming

Quick Tip: Powder Power

a piece of turquoise sheet glass with a layer of powder, followed by examples of turquoise fired with and without powder

A thin layer of powder has power! Light Turquoise and Clear Powder (001101-0008-F), unfired.   Same, capped with Tekta Clear & fired with schedule provided. Very small bubbles.   For comparison, same sheet glass lay-up fired without powder to a basic full fuse. Typical champagne bubbles.

Want to minimize the look of bubbles in fused pieces? Here’s a technique—used in kilnforming circles for many years—that’s also worked well for us.

Add a light application of Clear powder between the layers with a full-fuse firing schedule. That's right: between the layers! You'll actually trap more bubbles, but they'll be smaller than the usual "champagne" bubbles—and to that we say, "Cheers!"

Tip: To get an even distribution of powder, keep your sifter at least 18 inches (45 cm) above the surface and apply with multiple light taps to the handle.

Modified Firing Schedule

Rate Temperature Hold
300°F (167°C) 1225°F (663°C) 1:00
600°F (333°C) 1490°F (810°C) :10
Anneal and cool based on thickness.

This firing schedule has a built-in "bubble squeeze" when the glass is in the 1200-1225°F range. The glass softens in this range and, as the layers settle, much of the air is squeezed out. We've tested this extensively on 6" x 8" tiles. For larger works, you may want to extend the hold time at 1225°F.

Note that the smaller bubbles created by this technique can also result in a flatter piece, whether it's fired with transparent, opalescent, or iridized glasses.

Angelita Surmon, Oak Island Reflections (detail), a landscape panel in glass

Angelita Surmon, Oak Island Reflections (detail), 8 x 12 x .25 inches, 2012. Surmon uses a variation of this bubble control technique to draw attention to imagery and quiet the negative spaces in her kilnformed landscape works.

Downloadable PDF
Quick Tip: Powder Power

Helpful Resources

Video lesson: Working with Powders on Sheet
Video lesson: Heatwork and Frit
TechNotes 5: Volume and Bubble Control