Quote Originally Posted by Michael Mutmansky
Terrance,

There are other sources for high UV transmitting glass other than copier glass.

What people want to look for is 'low iron' glass. This glass is sometimes used as framing glass because it looks very clear, without the greenish tinge of normal glass. 'Water White' is one trademarked name, by Denglas.

My information searches in the past indicated that typical low iron glass has about 1/3 the UV blocking of normal (borosilicate) glass. The difference is not great in the final exposure time, so I wouldn't go out and replace all your glass unless you have a reason to, but if you do need to, you may think about getting low iron glass.

---Michael
Another "low iron" glass that transmits a higher percentage of UV radiation than regular float glass is a brand called Starfire.

I have personally tested a number of speciality glasses with increased UV blocking, including Starfire and Denglas, and agree with Michael that the difference in exposure time is very small, at best about 1/4 to 1/3 of a stop when evaluating glass of the same thickness. In my own case I considered the pros and cons of replacing the plain float glass in my two UV exposure units with one of the speciality glasses, but eventually decided that the small increase in printing speed was simply not worth the time and expense of doing so.

Sandy King