U.V. Denglas vs. Museum Glass

Doug Gemmell

SGF, Supreme Grumble Framer
Jun 17, 2002
Everett, WA
I am thinking about switching from Museum Glass to U.V. Denglas. The reasons are that it is slightly cheaper and doesn't appear to have the heavy ripples that have gotten more pronounced on the Museum. Does anyone have an opinion on which is the better product for the price?

This has nothing to do with our 2 boxes of Museum that were marked on the wrong side. Yesterday, someone who works at Aaron Bros. told me they had also gotten some that were mis-marked so I'm not crazy after all! Not on that subject anyway.
I've used Denglas and don't like it... but I've never used Museum glass, so I have no frame of reference for comparison. Some of the problems I've found with Denglas is that you need a special cleaner for it and It still ends up really streaky, and all you have to do is look at it funny and it'll get a smudge. Could be an operator problem, too, though.
I seem to remember sitting in a mini-convention in a mild stupor because they had put me in the "annex" that they forgot to tell the framers about....

Anyway, the Denglass lady was there, across from me, and I'm sure out of boredom, every 20 minutes would go completely through her speil...

Mostly I wasn't paying attention because of my early <strike>revulsion</strike>experience with Denglass...

but be that as it may, and I should pay attention, because things do improve and change, I seem to remember her saying "use any cleaner"....

But I would check with Denglass, first.

And yes, I have notice the sheeting of the coating lately... and the marking on the wrong side....but then with my reading handicap, I check anyway. :D
I guess the first question I would have is availability. I do like the Denglas' surface better (dipped as opposed to sputter coated on the TruVue products).
I have visited the Denglas booth at every trade show I attend and despite numerous requests still haven't received the samples. It kinda begs the question of customer service.
I would like to have the choice, but until Denglas is able to re-establish a distribution network and exhibit bettercustomer service habits, I'll stick with the TV.

OOPS...went to their website, and they are distributed in Florida...just not here. This is the Grumble isn't it?
I am not sure, but I think you are talking apples and oranges. Or maybe Macintosh versus Cortland.

Museum Glass is an anti-reflective glass with UV coating. The UV Denglas is actually a regular glass with UV coating. The UV Denglas is a "competitor with Conservation Clear and as such is (usually) a little more money. It is dipped instead of sprayed which elliminates the orange peel effect. It is also 2 mm instead of 2.5 which allows it to fit in some rabbetts that the TV doesn't.

I use then all for different applications.
I think you're right Cliff.

There is DenGlas and then there is Water White DenGlas. And there is Water White UV DenGlas.

I am under the impression that UV Den is more accurately compared to Conservative Clear UV and that Museum Glass should be compared to Water White UV DenGlas.

Den, as I am under the impression is a low iron glass (not unlike Guardian Glass) and while "clearer" less green tint, it is also brittler and required a clean wheel for cutting, and more care all around in its use.

I like Den, but I want to be able to compare like items to like items. I may be wrong about today's Den, as I haven't had the pleasure of talking to a Den rep in years. But that was what I gleaned from previous talks with them, and I stand by them!
I use both Tru-View's UV clear and museum glass and Denglas's UV clear and Water White.

For museum glass, I prefer Tru-View. DenGlas is slightly less expensive, but reflects a blue tinge when looked at from the side. Tru-view reflects more of a green tinge. Also, DenGlass tends to have to be handled a little more carefully if cleaning is needed, otherwise permanet markings occur. The DenGlas is also dipped and coated on both sides so there is not a right or wrong side. TruView scrathes much more easily on the art side, whereas DenGlas is much tougher, but has more streaking/spot problems.

Water White is a unique glass that should be considered for every framer's arsenal of glazes. It is crystal clear and thinner and is amazing when used with photo applications. However, it's downfall is that it provides minimal UV protection.

Dave Makielski
The latest industry information about glazing is "A New Look At Glazing", an article in the September issue of Picture Framing Magazine, which includes a chart of what each framing glazing company offers -- both glass and acrylic.

According to the table on page 68, Denglas does not offer any product similar to Museum Glass. Denglas offers UV-filtering clear glass similar to Tru-Vue Conservation CLear, and anti-reflection coated glass similar to Tru-Vue "AR".

It could be that the anti-reflection Denglas costs less than Museum Glass, but it does not have equal UV-filtering capability.

When comparing prices it is important to make sure the comparison is "apples to apples".

I don't have any experience with Denglas, because both of the distributors who deliver to my shop stock the full line from Tru-Vue, and I am pleased with the products. For me, whatever price advantage Denglas could have (if any) would certainly be lost in shipping cost.
Thanks for the info on streaking/cleaning problems Framinzfun, Baer, and Dave. I will certainly take that into consideration. It may be the deal killer in my switching as I don't need any more problems in trying to produce a quality product!

I left out a feature in my initial post: AR. The sample I got from the rep says "Anti-reflecting UV Blocking Denglas".

I think the comparison with Museum is apples to apples in this case. Visually they are very similar in a side by side comparison, with the exception of the very noticeable ripples on the Museum. The Denglas rep said the published UV blocking percentage is slightly lower than that claimed by TruVue but the tested spectrum range is broader so they provide about the same protection.

Jim, it appears that the table in Picture Framing Magazine should have listed Denglas under the "UV Filtering Anti-Reflection (coated) Glass" section since those properties are claimed on this glass by the manufacturer, unless they know something we don't.
Yeah, I was always under the impression that all Denglas was anti-reflective and coated rather than etched. Otherwise it wouldn't be "Den". If I remember correctly, the name comes from Denton Vacuum, which originally developed the anti-reflective property for airplane instrument displays.
:cool: Rick
Denglas did have a UV filtering A/R product at one time. It was a laminated glass and acrylic sandwich requiring special skills to cut and finish. Neat stuff, and essentially bullet proof, but a bit spendy for our market. As I remember a 24 x 30 lite cost about $175.00 back in the early 90's.
Originally posted by Doug Gemmell:
[Q]...I think the comparison with Museum is apples to apples in this case... The Denglas rep said the published UV blocking percentage is slightly lower than that claimed by TruVue but the tested spectrum range is broader so they provide about the same protection.

Jim, it appears that the table in Picture Framing Magazine should have listed Denglas under the "UV Filtering Anti-Reflection (coated) Glass" section since those properties are claimed on this glass by the manufacturer, unless they know something we don't.
Manufacturers' published data holds the answers. It is a mistake to rely on any sales person's opinion or interpretation of the data - look at the numbers yourself and then decide..

Your Denglas rep may be leaving out some details. Every glazing supplier in the PFM article reviewed & agreed with the data in the table, including Denglas.

As I recall, Tru Vue "AR" filters 78 percent of UV light between 250 and 400 nm. Museum Glass filters 98 percent. While those ratings may be called "close", they certainly are not comparable products.

I think you will find that Denglas is comparable to "AR", not Museum Glass.

According to PPFA and the conservators they consulted in developing the MCPF exam, 98 percent UV filtering is considered "Preservation grade" glazing. 78 percent UV filtering is not.
The Denglas coating that is applied to it is very scratch resistent. Its dip-coated and then baked at some ungodly temp. I've had the pleasure of using Denglas for the past few months and find it very user friendly, something that couldn't be said of its product back in the day...
The filtering stats on WW Denglas(low iron, anti-reflective) is in the 30-35% range on account of the low iron, but the clarity of the glass compared to regular glass is amazing.
Regular Denglas is an anti-reflective glass(read non-glare) with uv filtering in the 50-55% range.
UV Denglas is coated and baked on creating a smooth, non-rippled coating. It compares favorably with cons. AR but the difference is the coating used. Its an inorganic barrier which does not break down over time and casts a green light refraction instead of blue.UV blocking is in the 90% range.
Thanks everyone for the great information! I'll give the AR UV Den a try and we'll see what happens.
Hi... if I might add a few "cents" worth from this side of the pond....

Denglas UV Clear, TV ConClear and Guardian Inspiration UV are all basic UV filter glasses with no low-reflectance properties - in other words they are 2mm/2.5mm float with UV filtering. All hit good UV numbers well into the 90% plus range (300-380 nanometres). ConClear and Inspiration are made on Guardians "Extra-Clear' float glass. I don't know which substrate Den use for UV Clear. Exta-Clear is a float glass with improved transmission figures and reduced colouration. It is not a true low-iron ("water-white") glass but benefits from some very clever chemistry.
TruVue also use ExtraClear as the substrate for their AR and Museum products.

True low-iron glass (Guardian UltraClear, PPG Starfire/Solarfire and Pilkington Opti-white) are - as many have already stated brilliant, clear, colour-free glasses with very high visible light transmission - and are really great for framing.
Unfortunately, they also transmit a lot more UV than regular (greenish) glass and therein lies the problem. To hit the expected 97%+ UV numbers on regular glass substrate is difficult enough. To do it with low-iron (with up to 20% greater UV transmission) is much harder. The problems are made even worse when low-reflectance (AR) coatings are applied. These multi-layer coatings can reduce reflection of visible light from the 8.5% average for float down to as low as 0.5%. You don't need a math degree to figure out that means 8% more light for a UV filter coat to deal with. So, with a low-iron (water-white) float AND low-reflectance coatings it's almost impossible to hit the high 90's in UV filtering without resorting to laminating.
Thus, Water-White Denglas - that paragon of clarity, true colour rendition and low reflectance only filters some 30-35% UV (300-380nm). Schott's Miroguard is only a bit better and neither are designed or promoted as UV products. However, when laminated they hit 99% UV and retain their optical advantages but at a cost in both $$ and thickness.

In practical terms, which basic UV clear glass you use is down to price and local availabilty/distributor. TruVue's Con Clear seems to have good availability and price but suffers from the heavily rippled coating. Guardians is still in development but is showing great promise with invisible coating and keen pricing. Den is a very nice product and easy to use (cut and instal either way round etc) but is a bit more costly.

For low-reflection(AR), low-colouration(WW) UV glass, it is down to TV Museum with the rippled coating and dull appearance (but at a relatively low price) or a water-white laminate which really hits the spot but is costly and difficult to cut. Schott's lovely 2mm Miroguard Plus hits 82-83% UV and is reasonably priced, but can be a difficult sell due to the low UV number.

The trend here in UK is rapid growth in the use of basic UV glass - where there is only a small extra cost (an easy sell) and for the high-end collectors etc to go for laminated WW/AR where UV is an issue or WWDenglas/Miroguard where UV can be controlled (by filtration, laminated glass in the windows etc).

The speciality picture glass market is growing rapidly and this will surely attract new product developments over the next fer years.