UV Glass

[John]

Thanks Jim I think I'm getting this glass thing into perspective. For now, I will stick with the plain glass until the price of the uv is more in keeping with the extra filtering it provides.

Compared to the use of acid free materials, which is usually easy (and relatively inexpensive) to achieve, the cost of UV glass seems to be way out of proportion to its benefits. Of course in the case of a national treasure, whether in fact or just in the eyes of its owner, I will still recommend that extra bit of protection which is provided by UV glass.

Regarding the off-gassing of plastic at 150*F, I'll just have to switch on the air conditioning - though what will I do when summer comes? (Those Irish heat waves!)

[James Miller]

...Regarding the off-gassing of plastic at 150*F, I'll just have to switch on the air conditioning - though what will I do when summer comes? (Those Irish heat waves!)

Please understand that my comments are hear/say. I have no confirmation or proof of harm at that temperature. I'm still asking...

Of course, the offgassing might be of no consequence in some jobs. We all must judge the merits of protecting each job-at-hand from expected and/or unexpected environmental hazards. How much preservation do you want?

If we line the rabbet (excuse me, rebate) with a gas-impermeable barrier such as Lineco's paper-backed foil tape, I'm confident that the plastic's chemical properties would be the least of worries in event of a high heat situation.

[John]

http://www.thegrumble.com/ubb/ultimateb ... 1;t=010354

A picture is worth a thousand words!

[realhotglass]

Complicated subject !
And lots of misconceptions can be found.
Having experimented a fair amount, including independent tests of results (similar to the US thread posted above), it is my view that :

- UV glass indeed works, and well, to *DELAY* UV damage.
- If artwork is placed near brightly (sunlit or artificially) lit areas, it will fade gradually from the visible light too.

I have seen a US framers site that really sinks the boot into UV glass, stating their tests have proven it's a waste of time and $.
In their tests they put the framed prints right in the sunlit windows !

Samples I have made include newspaper banners with 1/3 each plain glass, UV clear - Guardian, and UV clear - TruVue. 2 brands of uv to see if both performed similar (they did).

2 hours in direct sunlight gives you an excellent sample showing the part under normal glass very yellowed, and the UV glasses still nice and white.
However, after 14 months or so, the UV sections have almost caught up with the plain glass section in discolouration.
Obviously the high lignen in the newspaper (?), but can be a good, quick, and easily replaced sample to make for your shop. Just replace as needed.

BTW, I don't think an original piece of newspaper (if valued) should ever be framed, make a copy to frame, and get the client to keep the original in an archival folder in a drawer somewhere.

My next sample will be faded with a pure 366nm black light. This should stop the UV sections from going off. I have a nice red gloss print, and a maroon mat, so these should be affected particularly fast under the plain glass.

Such a light a great sales tool as well ! If you put a white sheet on the bench, turn the UV light on above it, and move an offcut of uv between, it completely removes the UV 'glow' from the paper. A great practical demo.

Be careful with prints to use in samples. Many modern prints are using VERY good inks that just wont fade in the sun. Choose a glossy magazine pic, nice calendar pic, or similar. One might argue why use uv glass on these quality modern prints (that are guaranteed from uv damage for up to 80 years or so) . . . well mats / mounts will certainly benefit from the uv block too.

OK, a few points about some previous posts here . . .

Jerome said UV glass filters only 40% in 300 - 380nm range.
I'm almost SURE Jerome meant plain glass.
Both major worldwide brands of UV, Guardian and Truve, block ~97% minimum.

Non reflective (diffused) will stop more uv light than plain clear glass, somewhere up ~ 55% - 75% depending on brand.

Low iron (waterwhite, starphire, etc) will allow a lot MORE uv light through than normal float glass (the iron in normal glass must have a blocking effect).

No uv glass should block higher that 380nm. Visible light starts at 400nm, and above 380 will interfere with viewing clarity.

Denglas (one s) is a low reflection coated glass, similar to TV reflection free. There is a uv product . . . Denglas UV. This is similar to TV Museum, just a little different in manufacturing technique. It is actually better is several ways, incl. can be cut either side and glazed either side facing out, highest clarity / visible light, tougher coatings.
Take a look at Denglas although I just went to get direct links, but couldn't get onto the site.

A few tidbits I've found about uv light . . .

Probable relative damage (PRD) can be measured.
UV light at 300nm = ~ 8 PRD
UV light of 380nm = ~ 1 PRD
Visible light at 500nm = ~ 0.03 PRD
. . . UV light is obviously very important to negate.

UV light ranges
Vacuum UV 40nm - 190nm
Far UV 190nm - 290nm
UVC 220nm - 290nm
UVB 290nm - 320nm
UVA 320nm - 400nm
Visible light is over 400nm
Infrared is over 800nm

UVC is excluded by the Earths atmosphere
UVB cannot pass though window glass
UVA is taken care of by UV glass in the framing

~ 6% of total solar energy is UV light in the 320nm to 380nm range.

I have lots more info, oh boy, do I.
But I think that's enough to absorb for a while . . .