Quick Tip: Circles from Squares | Kilnforming

Glass for Art and Architecture

Quick Tip: Circles from Squares

Circles from squares

You can create nicely rounded cabochons from stacks of 0.75"(20 x 20 mm) squares, thanks to heat, gravity, and the 6 Millimeter Rule. But be careful, they’re addictive!

Don't have time to cut them yourself? Pick up a jar of these pre-cut squares.

The Stack
Top (6 mm): A “lensing” layer of Clear. This layer will stretch considerably.
Middle (3-4 mm): This “design” layer will stretch and be visible through the top layer. Use part sheets or pieces of 3 mm sheet glass.
Bottom (6 mm): Typically not visible from the front. This layer will stretch the least.


  1. 6 mm Tekta Clear is a natural for this project. It’s more efficient, with fewer pieces to cut, clean and assemble! Measure and score a grid of 0.75" squares, then run them using the Rule of Halves. Two layers of 3mm will also work.
  2. A dab of GlasTac Gel will keep the stack together before firing.
  3. The stacks flow out to about 1.25" (32 mm) in diameter, so give them room.
  4. For the cleanest release, we recommend firing on ThinFire.

Cabochon Firing Schedule

Rate Temperature Hold
400°F (222°C) 1225°F (662°C) :30
600°F (333°C) 1525°F (829°C) :30
AFAP 900°F (482°C) 1:00
100°F (56°C) 700°F (371°C) :00
AFAP 70°F (21°C) :00

Note: This heatwork goes beyond what the glass is tested for. Some styles may opalize and/or shift in compatibility. Test before making multiples.

Some Design Layer Possibilities

  1. Blue/Vanilla part sheet: Scatter Steel Blue Opalescent coarse frit (000146-0003) onto a base of 3mm Clear sheet glass, then sift a heavy layer of French Vanilla powder (000137-0008) over the top to cover. Fire to a full fuse. Maximize depth by arranging the Clear side toward the top of the stack.
  2. River Rock Reaction (See Quick Tip: River Rock Reaction)
  3. Pieces of Citronelle Opalescent (000221-0030) and Turquoise Blue Opalescent (000116-0030).

Revised February 27, 2017.

Downloadable PDF
Quick Tip Circles From Squares