spreading glass

[deerick]

I'm making 4x4 coasters, bottom layer black with geometric shapes placed in the middle on top. Do I need to add a clear layer at the bottom to avoid spreading? Thank you

[Valerie Adams]

Do the geometric shapes cover the entire surface? If so, then they make up your second layer and you should be fine. If you just want them to be a design element on the top, I'd use thin glass (for the accents) but you may wind up with a hump in the middle, which wouldn't work well for coasters.

Probably best to do two full layers with a thin accent layer on top. For your design, I'd do the clear on top of the black, and then place the (thin) accents, so they have the appearance of floating a bit.

[deerick]

Update. Did one with clear on bottom and one with just elements on top. The coaster with clear spread but had a smooth finish on top. The one without additional glass did not spread but the glass geometric elements on top did not fully fuse into bottom layer causing the coaster to be bumpy. Next time I will put elements closer to edge