I'm sure there are several good glasses out there but I use CC and Museum for 2 reasons.
1. Both are made in the US. They don't come from Vietnam, China, or Europe. They are not contributing to our trade deficit.
2. The standard for UV is 97%. Museum and CC exceeds the standard. Yes, I realize there is little difference between 92% and 97%, and some fading is due to the visible spectrum, which none of the glasses filter for. And some of us may have problems with the standard.....
However, if I sell something and the artwork fades, even if it is because of exposure to the visible spectrum, I'm going to have more trouble defending myself. If it gets to depositions and I did not use CC or Museum (and yes, I have been in depositions) and the attorney asks "did you even frame to Minimum standards in place at the time?" and I say "no", and he then asks "Did you know what the MINIMUM standards were at that time?" Followed by "Why didn't you tell your customer you were NOT framing to even the MINIMUM standards?" No matter what you say, you have just lost. "You can always say, "well the Customer wanted something cheaper, or wanted to view the artwork better", but we are the experts and that carries weight.
Yes, I tell my customers that all artwork will fade over time, and some will even change colors in the dark, but this (CC or Museum) exceeds the minimum UV standards for UV glazing that are in place at this time. Yes, I have clear for corporate decorative work, but I have releases in place if anyone wants to use it.
Wow! I guess I'm glad I live in Alaska. I've never had anyone in the last 21 years even remotely come close to suggesting they would sue me due to fading of their artwork. I think it's my job as a framer, and printer for that matter, to advise people what products I'm using, and to point out the various UV protection of any glass I'm selling. I can also say that any competition that I have is probably using decorative matboards. Michael's, JoAnn fabrics, and most of the local framers just use decorative matboards. The bright white core of select matboards is a dead giveaway vs the cream color of decorative, and I just don't see conservation board being used. So, yeah those are acid-free, but hardly archival. Better glass may or may not help. For true conservation I am going to go to a rag mat anyway, and if someone's going to pay for that, then it goes without saying they're going to buy and use museum glass or CC.
I can say I feel much better about the Giclee's I produce using 100% pigmented ink on 100% cotton rag paper or canvas that is varnished with the proper coating, and that has been tested. Yes, even an authority like Henry Wilhelm many people have questioned, and he does a lot of the testing. Yes, certain ink and paper combinations will last 100 years, and that paper will probably fall apart long before it fades. Unfortunately a lot of the accelerated aging does not, and cannot, factor in everything that's going to contribute to the degradation of artwork.
So, I will go by current standards and advise people as to what is published out there, but I also doubt a UV glass that filters 92% vs 97% is going to amount to a visible difference given all the variables that cause artwork to degrade.
When you throw something out in the sunlight for three weeks behind glass of all different types, and they still fade to about the same degree, hmmm what does that tell you? Do you believe your eyes or the published data? Most testing is done in a very precisely controlled environment. It does not account for things like ozone for example. I have one paper I use in the shop here that is highly susceptible to ozone. It turns the paper yellow within weeks, yet is rated over "72 years before noticeable fading can occur" by Wilhelm research. We have millions of prints that were produced by one hour photo labs. Do you really think those shop owners paid super close attention to whether their stabilizers were fresh? I worked at several, and can tell you quality control was kind of lax. I worked in quality control in a large Los Angeles photolab for a number of years, so I could tell you some stories.
The custom labs of the time were fairly conscientious, but the largest part of the market was an amateur one, and I see photos that are less than 10 years old that are already starting to fade. I see artist coat masonite boards, that are loaded with glues/formaldehyde etc. Yeah, they claim the gesso coating isolates the art from the backing--okay maybe, maybe not. How about all those fumes from cleaning products you use for your bathroom and kitchen, or the leftover fumes from that T-bone you ate or cigarette you smoked, etc. etc.
These are but a few example. There are all kinds of variables out there, yet were going to be adamant about differences between 92 and 97% UV. I wonder how consistent the coating is on glass, yet another variable. I just got a batch of studio molding in last week that smells horrible. I have no idea what's in the finishes, but my sinuses are not happy, so I can only imagine what that stuff does to artwork as it outgases 2" away. I'm sure that extra 5% UV protection will take care of it though.
Troy