They probably use plexi in the gallery instead of glass to lessen the chances of breakage when the customer transports it.
If you are a business with tax numbers and such, you can buy from some of our distributors at our costs. Which is about what was posted earlier for Tru Vue museum glass.
Not sure what is meant by the statement by elliot: It seems there's museum glass and 'Museum Glass'.
Museum Glass is only sold by the company who uses that name for their glass and that is Tru Vue.
Any glass that costs several thousands per sheet is nothing I have ever known in the business after almost 18 years. A 4x8 foot sheet of Optium acrylic would cost me 41.50 per square foot if my supplier cut it for me. At that price, it would cost $1328 for the whole sheet. Optium is the plastic equivalent of the low reflection uv protecting properties of TV Museum Glass. Way more expensive but sometimes needed. If you come to me for any of this, you better believe it will cost you much more!! I run a business (theoretically) to make a profit. 2.5 to 3 times mark up is the norm from a frame shop.
If you ever get a piece of art to reach temperatures high enough to warp a piece of plexi, the odds are that you are storing it wrong... like next to a furnace for melting glass!
Even if you hang it so the sun beats on it every day, it wouldn't soften the plexi enough to allow it to warp. Again, for that to happen, it needs to be temps WAY more than the sun could give you.
Hanging it so the sun hits it WILL destroy the art quickly no matter WHAT you put in front of it. None of these products give 100% protection from the suns damaging rays. They only slow the process down.
Don't confuse reflection control with museum glass or Optium acrylic. A piece of reflection control plexi or glass has been micro etched and will diffuse the image even with only 2 mats on it. A piece of Museum Glass or Optium will still be almost crystal clear even in a deep shadow box. That's why it costs so much more... it does more.