The 6mm Rule for Glass Fusing

When glass is fired on a full fuse programme, it naturally wants to settle at a thickness of approximately 6mm.

• Less than 6mm thick: The glass will pull in from the edges as it melts, creating the familiar ‘dog-bone’ effect.
• Around 6mm thick: The glass will retain its original shape, producing the smooth, even finish expected from a full fuse.
• More than 6mm thick: The glass will spread outwards during firing until it reaches approximately 6mm thickness.

Remember: Every layer of glass, frit, powder, stringer and accessory contributes to the overall thickness. It’s easy to forget when adding decorative details, only to discover the glass fairies have reshaped your work by pulling it in or splurging it out!

This version is a little shorter, clearer, and easier to read at a glance while still explaining the science behind the rule.