Bullseye Opaline (style 000403) is a 90 COE fusible glass sheet, an opalescent color for fusing, slumping, and kilnforming. As a striking color, Opaline may not reach its final shade until it is fired.
Cold characteristics Bullseye writes these notes for the standard 3mm sheet of this color; this page is the 2mm thin rolled version of the same glass.
Appears transparent and clear in its cold form. Occasional wisps of white are possible.
Working notes Requires a full fuse to strike to a hazy, milky white that transmits warm-hued light. Transmitted light varies based on thickness: Thinner pieces result in a yellow-ish hue, thicker pieces in a warmer almost orange hue. Opacity increases with extended heatwork. Opaline may remain clear or largely unstruck at temperatures in the tack fuse range (1275°F, 1425°F). To achieve target color and opacity when used in tack fuse projects a single sheet can be pre-struck at higher temperatures (1470/1480°F for :10). Expect the edges of the sheet to pull in from the original footprint and consider firing on 1/16” fiber paper topped with ThinFire for sheets larger than 10×10”. This allows air to escape laterally, thus preventing it from gathering between the sheet glass and kiln shelf in the form of a large bubble. The resulting struck sheet can then be cut and used in tack fused or other lower temperature works. Take note that the resulting struck sheet will have trace amounts of ThinFire/Shelf Primer on the shelf side, which can affect the results in secondary firings. Additionally, the opacity of the Opaline sheet may continue to develop in subsequent firings. Overlay Information Opaline has great potential to expand the color palette in kilnforming because it has the ability to create new colors with distinct properties. For more information, see Opaline Overlays.
Reactions This color is not reactive. It can sit next to any color without forming a reaction line, which makes it a dependable choice for bases and backgrounds. See the Reactive Potential of Bullseye Glass chart to find the colors that do react.
Format and sizes Thin-rolled sheet, 2mm, with a rolled edge. The thinner sheet is ideal for overlays, fine detail, and controlling stack thickness. Available in the sizes shown above.
Fusing and compatibility Tested compatible with other Bullseye glass. When you combine it with glass from other makers, matching COE alone does not guarantee compatibility, so fire a small test tile first.
More of This Color The same Bullseye color in other forms: 3mm Sheet · Frit .
Helpful downloads What to Expect from Bullseye Glass (PDF)
Technical data courtesy of Bullseye Glass.
Description updated: July 7, 2026
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