glass with high UV transmission

revaz_kv · Oct 18, 2010

Hi everyone!

Does anyone know what glass should be used for contact printing frame?
I mean, is there a glass with very high UV transmission? Since better transmission means shorter exposure time.

There seems to be little info on the subject.
Any help is appreciated!

Michael A. Smith · Oct 18, 2010

Regular glass is all that is necessary. I am sure there is special glass, but think getting it would be an unnecessary expense.

Michael A. Smith

Shawn Dougherty · Oct 18, 2010

The only issue I've had involving print frame glass was Newton's Rings. That was solved by using reflection control framing glass with the slightly textured side toward the negative. I work in a frame shop so just used scrap but it's cheap, a kind framer might even give you a piece. Take your frame in so they can cut it to size.

Shawn

revaz_kv · Oct 18, 2010

Thanks for tips!
So, regular glass is ok for a vacuum frame, which I hope to build myself

What about plexiglass? Is it better when it comes to UV transmission?
I am asking because I saw a guy on youtube using plexiglass for his contact printing frame.

JSebrof · Oct 19, 2010

As far as glass that transmits UV, don't they make those special UV lenses out of quartz-fluorite glass? I don't know where you'd get that kind of glass in sheet form for contact printing though, or any other form for that matter.

Q.G. · Oct 19, 2010

They use fused quartz or fluorite. Pure.

Normal glass is mostly (fused) silica, with additions.

revaz_kv · Oct 19, 2010

JSebrof said:
As far as glass that transmits UV, don't they make those special UV lenses out of quartz-fluorite glass? I don't know where you'd get that kind of glass in sheet form for contact printing though, or any other form for that matter.

Quartz-fluorite > sounds very expensive:confused:

What glass is used in vacuum printing frames which are for sale at Edwards Engineered Products? Is it a regular glass or something special?

Shawn Dougherty · Oct 19, 2010

revaz_kv said:
Thanks for tips!
What about plexiglass? Is it better when it comes to UV transmission?

I remember reading somewhere that Plexi blocks more UV than regular glass. Naturally I do not remember the source. =) Might be worth checking into...

Michael A. Smith · Oct 20, 2010

We use regular glass in our vacuum frame.

Michael A. Smith

Poisson Du Jour · Oct 20, 2010

Calcium fluorite (CaF2) even better!

Failing that (by cost alone...) you could use an offcut of TruVue UV-retardant glass used in MGCF jobbing; most high-end frame shops use this, and all of my Ilfochromes have been framed under it since 1994.

tony lockerbie · Oct 20, 2010

Regular 2mm clear glass is the best option. Tru-vue do make a super clear glass, but that is more about removing that slight green tinge than increasing UV transmission. Don't use the Tru-Vue conservation glass because that hardly transmits any UV at all, great for framing, but would make a VERY slow sunlight printing frame!

tony lockerbie · Oct 20, 2010

Oh, forgot to mention that Perspex/Acrylic blocks a lot of UV, together with the static and scathing problems, would make that a bad choice as well.

Q.G. · Oct 20, 2010

Poisson Du Jour said:
Calcium fluorite (CaF2) even better!

That, spelled correctly as calcium fluoride, is the Fluorite already mentioned.

revaz_kv · Oct 20, 2010

Thanks for info!

So I will use regular glass
Regarding the thickness, 2 mm sounds good, although I am probably going to use something thicker and thus heavier

jp80874 · Oct 20, 2010

revaz_kv said:
Thanks for info!

So I will use regular glass
Regarding the thickness, 2 mm sounds good, although I am probably going to use something thicker and thus heavier

You say heavier. Is that because you think weight will add more pressure? The pressure comes from the springs (usually three) on the back of a contact frame or the suction of a vacuum frame.

If you contact print often or all the time there is wear and tear on the glass. Once or twice a year I replace the window grade glass in my contact print frame. Scratches, pin holes and other such damage are just a part of the work for me. It happens. These of course show on the print. I keep two spare glass pieces wrapped in paper in case I need a replacement suddenly, such as breaking it or scratching it. If glass is so easily damaged that is another good reason not to use plastic.

John Powers

glass with high UV transmission

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