Tuesday, September 28, 2010

Revealing the Tin Side of Float Glass with Ultraviolet Light

When plate glass (AKA: FLOAT GLASS)  is manufactured, one side of touches molten tin which leaves an invisible coating on the glass. The silver stain reacts differently with the tin & non-tin side. A short-wave ultraviolet light will reveal the tin coating which fluoresces with a milky white haze.
Beveled glass is cut from float glass and the manufacturers do not check to see where the tin side is. These two bevels would take stain differently.

In this example the tin side was on top and has been partially removed in the beveling process.


  1. Your pictures are quite helpful. That milky haze is difficult to determine. I remember you warning us about silver stain and its need for it's own kiln shelf. In the book, Warm Glass it says the silver salts interact with the tin producing a dark color whereas the non-tinned side is lighter? I am wanting to try it again and wonder what you advise? Carrie Heilman

  2. Just discovered your extensive sample page. Thanks. ps I did make to Brazil and managed to get some basic pictures of the cathredral in Curitiba. Glass researchers were there at the same time so maybe they will provide us with good images someday. Carrie

  3. why is it important to know the tin side of a float glass?