# Is glass uv protective?



## Derektees (Dec 6, 2016)

I'm building my own exposure unit and have a perfect sheet of glass to set the frames on, and which the florescent light would shine through. But, I don't know it it is uv protected. Does this matter or should I find a new sheet of glass that for sure isn't. Or is there a way to tell. Note: there are no labels on the glass.


----------



## splathead (Dec 4, 2005)

It matters. Exposure unit glass should not be uv protected. 

One way to test it is to do a test screen exposure. Place the glass on half your film, leave the other half uncovered. See how it washes out. Your uncovered portion will, of course, not be sharp. But you should be able to see if the washout effort is about the same for both sides.


----------



## zhongrunclt (Nov 7, 2016)

I think normal glass is not uv protective; only some speically glasses may be uv protective.


----------



## PatWibble (Mar 7, 2014)

Most 'normal' glass is UV protective. Most window glass will absorb all of harmful UVB light, and it can absorb around 40% of less harmful UVA light. 
Laminated glass will possibly absorb nearly all UVA light, depending on the lamination process.

If it is a piece that you have lying around at home then it will probably be 'normal' glass. Glass with little or no UV filtration is a specialist, and expensive, product, so the chances of yours being low UV are probably slim.

Most emulsions work in the higher end of the UVA light range, so normal, non laminated, glass will work ( badly), but will slow the exposure process down very significantly.

Build your unit, and replace the glass as soon as possible.


----------

