Sheet Opal Glass sources ?

[Jim C.]

I'm building a UV light box and eons ago I used opal glass sheets as diffusion
for backlit animation art, anyone know of a source of optical or near optical grade
opal glass .1875" ish ( 3/16" ) thick x 11 x 14 ?

I know Edmund Optical is a source but they list small sizes, and are pretty pricey.
My backup plan is to use translucent white plexi, but I'd rather have glass for the
rigidity because of the heat generated from the UV LED's.

[Pere Casals]

You may DIY make your own in 10min:

https://www.youtube.com/watch?v=XZ8FP0vJGMU

196817

Glass has to be very clean to have a uniform work

[Tin Can]

Plastic as Dustin Hoffman (https://youtu.be/PSxihhBzCjk)learned long ago

Some years ago I got a free oversize 4X8 ft sheet of this stuff, delivered in a huge crate

https://www.acplasticsinc.com/categories/light-diffusing-acrylic

[Eric Woodbury]

Before you get too invested, check that opal glass transmits the spectrum required.

I found this:

http://www.glassdynamicsllc.com/flashedopal.html

Looks as though transmission rolls off about 340nm. However, overall attenuation is high.

[Jim C.]

Acid etching is out, I looked at samples of acid etched and acis washed glass at a glazier today and it was like ground glass

Plastic is my fall back, but I'd rather not because of heat rigidity issues.

The UV LED's are about 420nm so if I'm reading the graphs correctly it'll be fine.

[Willie]

Might check with Stain Glass studio people as many of them have suppliers of all types of glass.

[Eric Woodbury]

At 420nm (still in the visible, surprised they call it UV), you're in-band with flash opal glass, however, in-band is only 35% transmission. That's almost 2 stops down.

What is the heat issue? UV is not thermal radiation and will only heat something if absorbed. Lower absorption would be less heat. Since the LEDs are narrow band energy and not black-body radiators, they will produce very little heat, even when absorbed.

(Wear yellow glasses or sunglasses during direct exposure to this radiation. Since the human eye does not see violet very well, the iris in your eye will not constrict as much as it should to protect your retina. This can produce headaches and eye damage. )

BTW, to answer your question, last time I bought flash opal, I purchased it from a glazer. Local glass shop had it.

Cheers

e

[Jim C.]

At 420nm (still in the visible, surprised they call it UV), you're in-band with flash opal glass, however, in-band is only 35% transmission. That's almost 2 stops down.

What is the heat issue? UV is not thermal radiation and will only heat something if absorbed. Lower absorption would be less heat. Since the LEDs are narrow band energy and not black-body radiators, they will produce very little heat, even when absorbed.

(Wear yellow glasses or sunglasses during direct exposure to this radiation. Since the human eye does not see violet very well, the iris in your eye will not constrict as much as it should to protect your retina. This can produce headaches and eye damage. )

BTW, to answer your question, last time I bought flash opal, I purchased it from a glazer. Local glass shop had it.

Cheers

e


They're cheapie eBay UV LED strips, who knows what the actual wavelength is, but it does expose the photo polymer that I have.

The heat I'm referring to is from the LED chip itself, the individual UV LED's on the strip
that I have give off quite a bit of heat when they're on, I'm measuring 96ºF per LED chip via an infrared thermometer.

I'll have to reach out to some more online sources to see if they have it, two local glaziers didn't have it or knew where to order it.
I am attaching the strips to 1/8" thick aluminum sheet which forms the back of the light box so it should heat sink the UV LED strips.

Jim

[Drew Wiley]

What Edmund lists on their amateur website is about 1% of their full industrial selection; and larger as well as custom sizes of opal glass are probably available. Yes, they're more a convenience rather than affordable source unless you are buying in industrial volume. True opal glass is relatively thick with quite a penalty in light transmission. I like to use "Sign White" Plexiglas from plastics distributors for efficient diffusion per se; but there is little doubt in my mind that this would block are certain amount of UV. But how much CUMULATIVELY in comparison to opal glass, I can't say. It's an interesting option simply because the overall light transmission is much higher than opal glass, and more UV bandwidth might get through anyway. But that in itself depends on the specifics being sought. Contact Jason (Nodda Duma) of this Forum; he has the right background as an optical engineer.