Tin Side of Window Glass on Molds

A little background information for anyone unfamiliar with fusing with window glass before we get started.


Float Glass: Also known as window glass. ‘Float’ refers to the manufacturing process, where liquid glass is floated on a bed of liquid tin to give it a super smooth optically perfect surface. This is the pretty standard manufacturing method for window glass worldwide at this point.

Tin Side: The side of the float glass that was against the molten tin. There is a very thin tin coat on the glass, not enough to see, but enough to affect fusing.

So, the never ending question is, what to do with the tin side, and does it make a difference? Let’s try some float (window) glass on molds and see what we see.


Bronze 6mm float glass (windows from an office building)

Short wave UV light

Safety Glasses


Prepared Beehive molds

Step 1 – Find the tin side. Take all of the materials into a dark room. WEARING the safety glasses, turn on the shortwave UV light. This light will sunburn you, and can cause cataracts, so please be safe. Safety glasses are a must, gloves are a very good idea.

The tin side will glow under black light. Interestingly, the tin layer varies quite a bit between pieces of glass, so you may get a strong glow, and you may not. Once. you’ve identified the sides, label them with your marker, I used TSU and TSD on mine to indicate the Tin Side Up and Tin Side Down.

Step 2: Fuse the glass on the molds

The circles I’ve cut are sized for the Beehive Mold, so I’ve kiln washed them and put them into the kiln with one mold having the tin side up, and one the tin side down.

Bronze window glass on molds

Step 3: Fuse

I fired these to a full fuse using a simplified schedule: (in F)

300/hr to 500 h 15

300/hr to 1100 h 15

500/hr to 1550 h 8

9999 to 1060 h 30

200/hr to 700 then off

Now let’s look at the other side:

It seems pretty clear that the glass with the tin side DOWN against the mold has much better detail and is quite a bit glossier.

Conclusion: It’s worth checking for the tin side if you are fusing window glass on molds.

Related Products:

Beehive Mold

Related Tutorials:

Fusing with Window Glass Tutorials