Question about Float Glass & Texture

Q: I will be contacting you in the next couple of weeks about scheduling the private class with you. In the meantime, I have another question. Is it OK to paint on regular float glass assuming that I will use enamels later on it or is that a no-no? If so, what do you do if you do not want any texture on the glass you are painting on. Artique works great, but the kind I have has A LOT of texture and I would rather use something flat. What do you think?

A: Float glass has a tin coating on one side that will affect silver stain and some enamel colors. You should always test float glass with a short wave ultraviolet light (sometimes marketed as a Tinscope or Tin-light). Mark the appropriate side of the glass for your use. Silver stain takes more intensely on the tin side of float glass. Enamels are another story. Sometimes interaction with the tin side is bad. I have had problems with some blue, green & turquoise enamels going grey or black. Other enamels, especially gold based colors – like pink, magenta, red & violet actually are more intense and saturated on the tin side - go figure! The answer, if you haven’t guessed it, is to test each color first.

Here is the link to the page on this blog that references UV light & Float Glass: http://thepaintedwindow.blogspot.com/search/label/UV%20light

As far as texture goes, that’s a subjective call. Personally, I paint on mouth-blown Lambert's or Desag (which is similar to Artique). I prefer the texture of these glasses. If I’m painting a face I would avoid a mouth blown glass with a lot of seeds and choose something smoother but surface striations are OK by me – that’s what we’re paying the extra money for after all! If you really find the Artique texture objectionable you can always flip it over – the back side is considerably smoother.

Happy painting!

Other Glasses which React to Ultraviolet Light

I found other examples of non-float glasses which react to short wave ultraviolet light. The reaction in the pressed jewel above is a result of the chemistry of the glass and not because of a tin coating. Can ultraviolet light be used as an indicator of how a particular glass reacts to silver stain?

Mouth-blown glass from St. Just shows a mild fluorescence compared to the Lambert's sample which shows no reaction.

Bullseye's "Reactive Ice" shows a strong fluorescent reaction. It also proved very reactive to stain.

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.