PDA

View Full Version : The effect of varnishing on lightfastness in oil paints


sidbledsoe
06-08-2014, 06:55 PM
I have read a lot of posts from Alex, Gigalot, and he has done different tests with various mediums and varnishes. What I am wondering is this, does anyone have any testing done, especially on fugitive colors, where they have attempted to protect and increase the lightfastness by the application of varnishes in particular.
I am asking because I don't want to spend a lot of time doing these tests myself, unless no one has ever done them before.
It seems logical to me that if some varnishes are more UV protectant than others, let's say like Gamvar vs Damar, that they would provide more protection from deterioration by light.
We know that watercolors are generally not as lightfast for the same colors as oil paints, especially those fugitive ones.
Thanks a lot if you have any real data, not just thoughts, that you could share on this!

Gigalot
06-10-2014, 04:37 AM
It might be very interesting. For example, I love "Naphtol" Most gorgeous paint in the world. However, ASTM-IV or ASTM-II, which is almost the same thing for artists. The verdict is "Fugitive" How much I can improve lightfastness adding something (Zinc white) in it, and using "Varnish" on top of paint?
How much I can reduce lightfastness adding cobalt siccative to a more "lightfast" pigments like Quinacridones and Pyrrole? Old manuscripts reported significant discoloration effect of copper salts, Vertdegrease e.t.c to organic lakes. But copper is much less aggressive siccative to compare with cobalt, which can promote chemical reactions in a very small concentration. I just remember Liquin darkening into the close jar. I added a trace amount of cobalt to fir sap and this fir drops turned brown around the area with cobalt resinate, while pure fir tears do not change color during more than one year.

sidbledsoe
06-10-2014, 11:56 AM
I use napthols all the time, they should be ok for art but not exterior, one of my faves is a mix of PR188 and PR112 in Lukas Cad Red Hue.
I even have some quite old watercolors (46 yrs) done with cheap pan napthol reds that are doing fine. My oldest painted piece with PR83 genuine alizarin crimson is about 40 yrs old and looks great.

Gigalot
06-10-2014, 02:50 PM
Yeah! Alizarin Crimson is an easiest pigment to replace. Tons of SUB are available, any Naphthol can replace it, PR146, PR187, PR57:1 or PR48:2. I can't determine which is which! Quin PR122, PR170 or Burgundian Winest Red PR177. All are good Madder lakes of petroleum rose! From any, random 50 pigments, 30-40 can replace Alizarin Crimson! :D I guess, under Cobalt pink glaze layer those pigments can stay 500 years in masstone!
But some gorgeous colours do not have a good replacement. And if the picture varnish or Zinc substances can extends their lives in floral paintings, I will be glad!

Brian Firth
06-11-2014, 02:50 PM
I did a test with genuine vermilion to see if Soluvar varnish protected it from darkening in sunlight. It did not have any noticeable benefit as far as the darkening is concerned.

Mythrill
06-11-2014, 06:04 PM
It might be very interesting. For example, I love "Naphtol" Most gorgeous paint in the world. However, ASTM-IV or ASTM-II, which is almost the same thing for artists. The verdict is "Fugitive" How much I can improve lightfastness adding something (Zinc white) in it, and using "Varnish" on top of paint?
How much I can reduce lightfastness adding cobalt siccative to a more "lightfast" pigments like Quinacridones and Pyrrole? Old manuscripts reported significant discoloration effect of copper salts, Vertdegrease e.t.c to organic lakes. But copper is much less aggressive siccative to compare with cobalt, which can promote chemical reactions in a very small concentration. I just remember Liquin darkening into the close jar. I added a trace amount of cobalt to fir sap and this fir drops turned brown around the area with cobalt resinate, while pure fir tears do not change color during more than one year.

Giga, don't mix any fugitive color with Zinc White (PW 4)! It actually tends to speed up the fading of many of them much faster than either Lead White (PW 1) or Titanium White (PW 6).

What you could do is to replicate the technique of the old masters here: get a more permanent paint, and glaze it over the more fugitive. Van Eyck got his Indigo (NB 1) intact by glazing Lapis over it.

In the case of Naphthols, I suppose you could make the bottom layer (the one with the Naphthol) lighter and leaning to the opposite direction of the upper layer (glaze.) For instance, if you're using Naphthol Red Light (PR 112) and you want to protect it with a layer of Transparent Yellow Iron Oxide (PY 42,) you could try to make the naphthol underlayer slightly bluer and lighter, and then mix PY42, filler (like your Alumina Hydrate) oleogel, and create a beautiful transparent layer of warm yellow that will be absolutely permanent.

I've actually done this with Dioxazine Purple (PV 23) by glazing Ultramarine Violet (PV 15) over it. Since there seemed to be no shift in acrylics when glazing, as Ultramarine Violet is very transparent, I didn't need to tweak the tints of Dioxazine Purple.

Gigalot
06-12-2014, 04:14 AM
Vermilion has a good reputation in oil medium. Varnishing might be useful thing but I don't know real mechanism of pigment darkening. Is it chemical reaction on light or it is crystalline structure changing? If it is structure changing, I guess, vermilion crystals must be doped with other chemical elements to stabilize it's structure.

Mythrill
06-12-2014, 04:07 PM
Vermilion has a good reputation in oil medium. Varnishing might be useful thing but I don't know real mechanism of pigment darkening. Is it chemical reaction on light or it is crystalline structure changing? If it is structure changing, I guess, vermilion crystals must be doped with other chemical elements to stabilize it's structure.

UV rays also change the structure of the pigment, Giga. This is why they fade.

Of course, darkening, fading or overall changing can also be caused by reaction with one pigment with another (more common with older pigment types,) or simply pollution.

Vermillion (PR 106) was usually protected in oil paintings with a glaze of Alizarin Crimson (PR 83,) which also made it look that vibrant. Even if the Alizarin Crimson would fade, the layer would still slow down the darkening of vermillion.

Of course, any quinacridone pigment could replace Alizarin Crimson's role if you ever need to touch a deadly tube of Vermillion. :)

sidbledsoe
06-12-2014, 07:32 PM
I could be wrong and I think there is debate about it, but I thought the darkening of vermillion was not a result of light exposure?

Brian Firth
06-12-2014, 07:33 PM
Where are you getting the information about zinc white being worse for fading? I don't think that is correct. Everything I have ever read put titanium white at the top for decreasing light fastness in tints. Do you have a source on that? I have seen where small additions actually increase lightfastness in tints, like with cobalt violet light. http://www.wetcanvas.com/forums/showthread.php?t=345990

And in my all my tests, on multiple samples, all genuine vermilion darkens on exposure to sunlight no matter what you do to it.

http://www.wetcanvas.com/forums/showthread.php?t=370339
http://www.wetcanvas.com/forums/showthread.php?t=605877


Soluvar and other modern varnishes, like Golden's, have UltraViolet Light Stabilizers in them, however the actual amount of protecting afforded by these is not significant enough to protect fugitive pigments from eventually fading.

Gigalot
06-13-2014, 03:12 AM
"Nanophase Technologies Corp offers zinc oxide nanoparticle additive called 'NanoArc,' which provides UV protection without affecting transparency, gloss, color, or physical properties."

Iron oxides, said to be a very effective anti-UV agents. I guess, a small amount of Tr.Iron oxides can also extend organic pigments life.

Aspsusa
06-13-2014, 04:33 AM
Timely thread for me, as I've been planning forever to do a few experiments/demonstration pieces with Golden's MSA varnish.

My plan is to actually take (presumably) very fugitive plain inkjet-prints, packaging, printed materials etc.
I am mostly inspired by the fact that there's a travel agent nearby that puts loads of brochures and poster (and model airplanes!) in their window which is right beside my bus stop, so I have had a very good view of what fugitive or "non-lightfast" means at its worst.
(The other impetus for doing this as an experiment is that the demo-material Golden provides doesn't demonstrate the UV-protective properties of the varnish very well, since it is done over quite light fast colours - 1 year exposed in the window and no difference discernible, whereas _any_ packaging with printing gets noticeably fainter within 2-6 months.)

Once it stops raining I _will_ get this done (I don't want to mess with the MSA-spray indoors if I don't have to), and once I get the hang of it with printed materials I might also do one with the most fugitive of the water colours I have on hand.

Oils or acrylics are more difficult, because I don't think I have any available with sufficiently bad lightfastness - I'm rather impatient, and without artificial light to simulate years of exposure any such experiments might take a really long time.

sidbledsoe
06-13-2014, 01:01 PM
thanks guys, I think I will go ahead and do some test myself with some oil paints.

Mythrill
06-13-2014, 03:55 PM
I could be wrong and I think there is debate about it, but I thought the darkening of vermillion was not a result of light exposure?

You're correct. But somehow, layering one color over another will either slow or stop the effects of UV light over the underlayer color.

I suppose that the upper color has a "sunblock" effect, much like the sunblockers we use to protect our skin. But since some colors are fully protected (lapis upper layer + indigo under layer) while some are only partially protected (alizarin crimson upper layer + vermillion under layer,) I think the interaction between several pigments might be more complex than we can imagine.

Mythrill
06-13-2014, 04:06 PM
Where are you getting the information about zinc white being worse for fading? I don't think that is correct. Everything I have ever read put titanium white at the top for decreasing light fastness in tints. Do you have a source on that? I have seen where small additions actually increase lightfastness in tints, like with cobalt violet light. http://www.wetcanvas.com/forums/showthread.php?t=345990

Hi, Brian. Most of this information comes from handprint.com. Although the site author does not state the effects of zinc white fading by himself, I see some "Naples Yellow Hues" with pigments that should be absolutely lightfast (PY 35 + PR 101) fade very badly because there's zinc white in the mix (PW 4.) I just don't see this pattern with the same mixes and Titanium White (PW 6).

Of course, you're free to take all this with a grain of salt and check for any changes yourself; it could be that the fading of those Naples Yellow Hues were just due to unnamed amounts of bad PY 3 or PY 74.

As for Cobalt Violet Light (PV 14), I just saw your tests and I'm puzzled by what happened. All the cobalt paints I knew of, except for Cobalt Yellow (Aureolin, PY 40) were absolutely stable. Are you sure there wasn't anything else mixed to "brighten" your cobalt violet that could have been responsible for this hue change?



And in my all my tests, on multiple samples, all genuine vermilion darkens on exposure to sunlight no matter what you do to it.

http://www.wetcanvas.com/forums/showthread.php?t=370339
http://www.wetcanvas.com/forums/showthread.php?t=605877


Soluvar and other modern varnishes, like Golden's, have UltraViolet Light Stabilizers in them, however the actual amount of protecting afforded by these is not significant enough to protect fugitive pigments from eventually fading.
Brian, this would be interesting: what happens if you wait for your Genuine Vermillion (PR 106) to dry to the touch and then glaze it with Genuine Alizarin Crimson (PR 83)? Does Vermillion stabilize? Does the darkening slow down?

sidbledsoe
06-13-2014, 04:27 PM
You're correct. But somehow, layering one color over another will either slow or stop the effects of UV light over the underlayer color.

I suppose that the upper color has a "sunblock" effect, much like the sunblockers we use to protect our skin. But since some colors are fully protected (lapis upper layer + indigo under layer) while some are only partially protected (alizarin crimson upper layer + vermillion under layer,) I think the interaction between several pigments might be more complex than we can imagine.
Again, from what I have read, UV light has nothing to do with the reaction, so lighblocking is not a factor in the darkening, but I don't really know too much about it. I have read the National Gallery info. (http://www.nationalgallery.org.uk/the-blackening-of-vermilion-an-analytical-study-of-the-process-in-paintings)
A reaction with chloride ions is the best guess for the reason. I have never had vermillion and don't ever plan on using any, it is the deterioration of alizarin crimson, napthols, etc. upon exposure to light that I am interested in and whether any varnish can help retard the fading.

Brian Firth
06-13-2014, 05:00 PM
Mythrill,
I have noticed that on handprint as well, but I'm not sure if it's not just an attribute of white pigments in general as they all decrease lightfastness in tints. There really isn't a large number of tints he tested with both zinc and titanium to compare, just the few naples yellows. Perhaps zinc oxide is less inert than titanium dioxide, but I'm not sure about that or if it is particular to watercolors as I haven't seen zinc oxide singled out in other literature as particularly more effective at decreasing lightfastness. It would be worth further researching though and I can do some comparison tests in oils with pure zinc and titanium tints to see if there is a difference. The cobalt violet tests weren't done by me, but I have noted the color shifts in my cobalt violet lights as well with pure pigment mulled myself.

I have not tried to glaze with madder or alizarin on the vermilion. I will have to test this, but I am not optimistic that it would provide much protection as long as light is still penetrating to the vermilion layer.

Brian Firth
06-13-2014, 05:08 PM
Sid, I can tell you that I have tested it multiple times and sunlight definitely darkens vermilion as that was the only variable in my samples. One exposed to light and the control kept in the dark, both in the same room. Also note that the national gallery article discusses the variable "black spots" on vermilion whereas in my tests the entire swatch always uniformly greyed and darkened upon sunlight exposure.

Brian Firth
06-13-2014, 05:22 PM
Sid,
Also in reference to your original question, beyond the one test with vermilion I haven't tried to "protect" any other fugitive colors with a UVLS varnish. I have a particularly disastrous Holbien Chinese Red that I can test though. It claims to be PR188, but all other samples of PR188 I have are pretty lightfast, but this one is a real loser and fades rapidly. I will let you know in a few months!


This is what Golden has to say
"In our testing a 10 mil film of the GOLDEN Gel Topcoat provided a similar degree of UV protection as the same thickness of GOLDEN MSA Varnish w/UVLS, and greatly limited the fading of fugitive dye-based inks after exposure to 1600 hrs. in a QUV Weatherometer, at 140 F, with ambient humidity normally below 50%. The cumulative UV exposure correlates roughly to the amount of UV energy from 100+ years of typical indoor gallery-lit conditions. "

sidbledsoe
06-13-2014, 06:24 PM
thanks a lot Brian, I have that same tube of Holbein Chinese Red and love the color but fear the fading, I will include it too.
I have a PR188 in something else too, can't remember but I think it is Lukas.

Brian Firth
06-13-2014, 09:11 PM
Sid,
Just a reminder that I did test the Holbein Chinese Red in the past and it was by far one of the most fugitive colors I've ever seen in an artists' oil. Note the W&N PR188 second from the left did just fine.

sidbledsoe
06-13-2014, 10:25 PM
Thanks, if they are really both PR188, and I would think that they really are, then the pigment that Holbein used is some kind of variation that is just plain crap!

Mythrill
06-13-2014, 10:45 PM
Thanks, if they are really both PR188, and I would think that they really are, then the pigment that Holbein used is some kind of variation that is just plain crap!

That happens a lot with organic pigments, Sid!

Winsor & Newton actually had a problem years ago with their Transparent Yellow Iron Oxide (PY 42) in watercolors, as handprint.com says. That's damn hard to achieve, but somehow they managed to get their samples to discolor and become gray. I suppose the tubes had some sort of impurity in them.

Surprisingly enough, though, Winsor & Newton seems to make outstanding organic pigments I'll give them that. I told people here about this before, and their Dioxazine Purple (PV 23), which is very bluish, somehow just won't fade even though the bluest shades are usually among the poorest in lightfastness!
An outstanding pigment they have too is Perylene Maroon (PR 178). It's pretty much the only pigment in handprint.com that gets a full 8,8 Blue Wool Scale again very surprising, considering their version is the reddest and most saturated!

Aspsusa
06-27-2014, 09:53 AM
thanks guys, I think I will go ahead and do some test myself with some oil paints.

How are the tests going, sidbledsoe?

Once it stops raining I _will_ get this done (I don't want to mess with the MSA-spray indoors if I don't have to), and once I get the hang of it with printed materials I might also do one with the most fugitive of the water colours I have on hand.

Well the weather isn't quite reliable yet, but hopefully soon, so:

Oils or acrylics are more difficult, because I don't think I have any available with sufficiently bad lightfastness

I need some advice on what oils to test, and I am a bit intrigued by the mention of zinc in mixtures making other colours less lightfast.

I have a few beer mats (yes!) that I have gessoed, and I thought I'd use a few for this experiment: put some oil colours straight from the tube (or mixed with some zinc?) on them, let dry and then cover half of the mat and apply Golden's MSA spray varnish on the other half. Put in a sunny window. See what happens.

But which colour(s) should I use?

Candidate 1:
I have a small old (late 80-ies/yearly 90-ies) tube of Winton Sap Green, which is labeled:
"Ferrous beta naphthol complex, Tartrazine lake (Acid G1/Y23)",
and I managed to find some reference to this edition of Winton Sap Green being "bad" or "fugitive", but I can't find anything definitive on the "Acid Green 1" part of it - the more descriptive name seems very close to one of the names given to PG8 on artiscreation.com, but I find it listed as "PG12" on the (fabulous) Finnish website coloria.net. And PG12 is not found really anywhere. At least not with my weak google-fu.
"Acid Yellow 23" seems like it could be PY100, and that at least is found on Artiscreation.com and given the lightfastness rating of IV.
But OTOH it also says Permanence: *** on the tube, so...

Candidate 2:
From the same old (unused!) Winton set the Alizarin Crimson, PG83. Again the tube says Permanence: ***, but...

Candidate 3:
Aureolin from Gamma (Klassika-series).
Here the lightfastness on the tube is given as **, so maybe promising. Unfortunately no pigment numbers, but I believe it is the real deal, ie PY40.

Candidates 4-n:
Something from ridiculous set of 24 mini-tubes of Reeves Simply. Unfortunately no pigment numbers or lightfastness ratings. Anyone have a good guess on what might be really fugitive in such a cheapy-cheap set of oils?

I can't make a ton of different test-pieces (not enough gessoed beer mats!), only maybe 2 or 3. I don't think I want to try to fit more than max 2 colours per piece, preferably only one really.

Suggestions for which I should start with?
And how about that zinc-factor? My zinc white is a blend of zinc and lithopone (pw5), if that makes a difference.

Obviously I don't want to introduce even more variables by mediums (beyond wetting the brush in turps/oil), but I also don't want to have to wait weeks for the test-mats to dry so I can varnish them.
Just apply the paint very thinly and hope for the best?

Gigalot
06-27-2014, 11:00 AM
How are the tests going, sidbledsoe?



Well the weather isn't quite reliable yet, but hopefully soon, so:



I need some advice on what oils to test, and I am a bit intrigued by the mention of zinc in mixtures making other colours less lightfast.

I have a few beer mats (yes!) that I have gessoed, and I thought I'd use a few for this experiment: put some oil colours straight from the tube (or mixed with some zinc?) on them, let dry and then cover half of the mat and apply Golden's MSA spray varnish on the other half. Put in a sunny window. See what happens.

But which colour(s) should I use?

Candidate 1:
I have a small old (late 80-ies/yearly 90-ies) tube of Winton Sap Green, which is labeled:
"Ferrous beta naphthol complex, Tartrazine lake (Acid G1/Y23)",
and I managed to find some reference to this edition of Winton Sap Green being "bad" or "fugitive", but I can't find anything definitive on the "Acid Green 1" part of it - the more descriptive name seems very close to one of the names given to PG8 on artiscreation.com, but I find it listed as "PG12" on the (fabulous) Finnish website coloria.net. And PG12 is not found really anywhere. At least not with my weak google-fu.
"Acid Yellow 23" seems like it could be PY100, and that at least is found on Artiscreation.com and given the lightfastness rating of IV.
But OTOH it also says Permanence: *** on the tube, so...

Candidate 2:
From the same old (unused!) Winton set the Alizarin Crimson, PG83. Again the tube says Permanence: ***, but...

Candidate 3:
Aureolin from Gamma (Klassika-series).
Here the lightfastness on the tube is given as **, so maybe promising. Unfortunately no pigment numbers, but I believe it is the real deal, ie PY40.

Candidates 4-n:
Something from ridiculous set of 24 mini-tubes of Reeves Simply. Unfortunately no pigment numbers or lightfastness ratings. Anyone have a good guess on what might be really fugitive in such a cheapy-cheap set of oils?

I can't make a ton of different test-pieces (not enough gessoed beer mats!), only maybe 2 or 3. I don't think I want to try to fit more than max 2 colours per piece, preferably only one really.

Suggestions for which I should start with?
And how about that zinc-factor? My zinc white is a blend of zinc and lithopone (pw5), if that makes a difference.

Obviously I don't want to introduce even more variables by mediums (beyond wetting the brush in turps/oil), but I also don't want to have to wait weeks for the test-mats to dry so I can varnish them.
Just apply the paint very thinly and hope for the best?

Good candidate can be Hansa - Naphthols. The most sensitive pigments to UV, H2O2, and to oxidation with oil peroxides and prone to free radicals reactions. Lithopone presence is not good, because Zinc Sulphide is well-known, highly photo-active pigment, while Zinc Oxide reduce photo sensibility.
It is better to have Zinc White in a pure PW4 form. "Master Class" or something trusted, heavy weighted, Artists grade paint tube with Zinc.

PO13 Benzidine Orange - good candidate, it can discolor quickly to a completely white paint.
PG8, many people thinking as it is not lightfast, can be worst, It do not change color in my test on direct sunlight during half a year or more. It can show (sometimes?) very high performance!

sidbledsoe
06-27-2014, 12:49 PM
sorry aps but I have been to busy to start this yet and then it will be sort of long term at least months or so.

MikeH53
06-27-2014, 06:22 PM
Concerning the Holbein chinese red, and variations on the naphthol AS pigment, I think it's likely to be a less permanent variation of PR 188. I know Winsor & Newton used to have a watercolour called "rose carthame" that was listed as PR 188, in addition to their "scarlet lake" PR188, the former was slightly bluer, the latter slightly yellower, but their main difference was in lightfastness. "Scarlet lake" had, and still has a permanence rating of A (durable), whereas "rose carthame" had a rating of C (fugitive). I wondered if there was a mistake in WN's listings, but the photo above of the Holbein paint seems to corroborate with the existence of a yellower, permanent variation that is wtill widely available, and a bluer, fugitive one that has been largely phased out but still probably used in Holbein's "Chinese red".


P.S. The same old (1977) WN listings also show "vermilion" and "scarlet vermilion" PR 106 in both their oil and watercolour lines, my sample of "scarlet vermilion" looks like a match for Holbein's "French vermilion". Anyway, even in the 70s, when vermilion was still widely available, it was placed in the same durability category as alizarin crimson and rose madder genuine in both oils and watercolours, with the note that it "blackened if much exposed to the direct rays of the sun", and could not be "relied upon to withstand damp". I think that the idea of vermilion ever withstanding direct sunlight should be, at best, treated with extreme caution. All samples of the genuine article tested which were documented on these boards turned dark. Even when the stuff was still commonly found on artists' palettes, this property was noted. Nineteenth and early Twentieth Century writers may have spoken of permanent vermilions, but this was probably due to a different notion of permanence, i.e., that was a time when alizarin crimson and aureolin were considered permanent. Going back further, genuine cinnabar in Roman ruins, when exposed to direct sunlight, turned dark. Vermilion, sooner or later, will darken in direct sunlight. I'd even suggest using that property to test whether or not one has the genuine pigment. The bright vermilion still visible in galleries is likely due to the paintings being placed away direct sunlight or to restoration work, not to some mysterious property of old vermilion or failure of modern vermilion. That said, vermilion can retain its brilliance if proper care is taken, but it's a wild goose chase to search for a vermilion that will withstand abuse the way modern cadmiums or pyrroles can.

briantmeyer
06-28-2014, 06:29 AM
There is this article on varnishes (http://www.goldenpaints.com/justpaint/jp14article2.php) that golden did.

I am going to have to do my own tests. I think anything you do just slows down the effects of aging, you could protect it via just not exposing it to light. If only 10% of the UV light gets thru, it makes it last 10 times as long, so it might be fine after a year, but after 10 years it looks like the unprotected sample after 1 year. I am sure that isn't the math involved, but that is how I think of it, it's just slowing down the exposure. Eventually you have to re-apply the spray, it loses it's effectiveness. ( it sounds like the absorbers protect the picture, the stabilizers just protect the spray. Just being behind a more solid material probably helps though as well as not all aging is caused by UV. I think watercolors are going to fade far faster than the same pigments in oils from my understanding. )

My goal is to use non fugitive pigments ( list on handprint as 8,8 or 7,7 if no other option ) then use protective sprays. Once I get a game plan together, then I need to take my chosen colors and do some long term testing without protection and perhaps using some different coatings ( wax or UV archival sprays, perhaps uv glass as well. )

sidbledsoe
06-28-2014, 09:38 PM
If only 10% of the UV light gets thru, it makes it last 10 times as long, so it might be fine after a year, but after 10 years it looks like the unprotected sample after 1 year.
Do you have reliable evidence, such as a test or study that verifies this claim that 10% UV light exposure equals 10 times less fading, or have you done this 1 year versus 10 year lightfastness test?
Many physical phenomena are non linear functions and/or require threshold energy levels before a reaction or change takes place. Factors such as those could mean that 10% UV light may result in 100 times less fading or possibly no fading at all. I have read at AMIEN that this type of thing is under long term study at this time.

briantmeyer
06-28-2014, 11:51 PM
That is why the next sentence says "I am sure that isn't the math involved, but that is how I think of it, it's just slowing down the exposure."

I am just saying that UV most likely isn't protecting it completely, but slowing down the process by some degree, much like accelerated testing simulates being displayed indoors for extended periods by increasing how long things are exposed. I don't even think if they can determine a percentage, but it seems like it is in fact protecting it if the report on the golden site is any indicator, but even then they measured slight fading per the graphs.

The bottle I have says it should be reapplied periodically to ensure continued protection. But again I don't know how often that needs to be done.

Gigalot
07-01-2014, 05:47 AM
T
The bottle I have says it should be reapplied periodically to ensure continued protection. But again I don't know how often that needs to be done.

UV chemical protectors rapidly decompose under UV light. Those protectors was designed to protect food from UV light, particularly, to protect vegetable oil ,packed in PET plastic bottles, against rancidity. . The plastic UV protected PET containers loose their protection effect after about 2-3 years according Wikipedia. But it is enough time to protect food.
This is a cause, why I have more interest to a inorganic protector like Zinc Oxide composition or something equal, rather than organic UV absorbents.

briantmeyer
07-03-2014, 06:46 PM
I am going to be doing my own lightfastness testing soon in watercolor, I just don't trust any of the information related to my medium outside of handprint.com and that is 10 years out of date.

I plan on including Krylon UV archival spray on half of the swatches, might also get some Dorland was as well, and see exactly how much protection they give for each color especially since the was does not have UV protectors. I might also get some more sprays for semi-gloss and full-gloss if I can, and perhaps another brand, but I'm limited on my budget. It might help just because it's got a clear coating over the pigments.

Still buying samples of various paints to use in this testing, and think I can borrow some colors from other artists as well, one of whom has a lot of Sennelier. ( want to start all the testing at the same time ). I have a lot of student grade cotman, koi colors, some reeves, daler rowney, in addition to my artist grade brands.

I have a known fugitive color ( aureolin ) so it should fade pretty quickly, might be able to determine how much difference in fading there is to a degree from the unprotected and protected, and comparing that to colors that fade at different rates. Might look at getting some original alizarin as well. Still I won't know for sure for another year, and until then it's more protection against dust, I am mainly relying on lightfast pigments.

It might take 3 years for the UV to break down, which I don't see as a bad thing, if I can determine a number of years or light hours, then I can know I need to re-spray every 3 years. It's still 3 years of protection which to me adds 3 years to the life of the piece which if I use a fugitive color might last only months. I'd assume my tests apply to a degree to other mediums using the same pigments, but I am primarily concerned with watercolor since it is far more likely to have fading issues.

Aspsusa
08-28-2014, 08:41 AM
I have a small update: since yesterday I have four small test pieces in a window.

They are the old Wintons (old version of sap green and alizarin) and the Gamma Aureolin, in various thicknesses and tints. On gessoed beer mats.
After letting them dry for around 5-6 weeks I masked parts of them and then applied Golden MSA spray Varnish, four coats.

It will be interesting to see what happens. Though I fear it might take a long, long time, as the placement isn't ideal.

Mythrill
08-28-2014, 01:32 PM
I am going to be doing my own lightfastness testing soon in watercolor, I just don't trust any of the information related to my medium outside of handprint.com and that is 10 years out of date.

I plan on including Krylon UV archival spray on half of the swatches, might also get some Dorland was as well, and see exactly how much protection they give for each color especially since the was does not have UV protectors. I might also get some more sprays for semi-gloss and full-gloss if I can, and perhaps another brand, but I'm limited on my budget. It might help just because it's got a clear coating over the pigments.

Still buying samples of various paints to use in this testing, and think I can borrow some colors from other artists as well, one of whom has a lot of Sennelier. ( want to start all the testing at the same time ). I have a lot of student grade cotman, koi colors, some reeves, daler rowney, in addition to my artist grade brands.

I have a known fugitive color ( aureolin ) so it should fade pretty quickly, might be able to determine how much difference in fading there is to a degree from the unprotected and protected, and comparing that to colors that fade at different rates. Might look at getting some original alizarin as well. Still I won't know for sure for another year, and until then it's more protection against dust, I am mainly relying on lightfast pigments.

It might take 3 years for the UV to break down, which I don't see as a bad thing, if I can determine a number of years or light hours, then I can know I need to re-spray every 3 years. It's still 3 years of protection which to me adds 3 years to the life of the piece which if I use a fugitive color might last only months. I'd assume my tests apply to a degree to other mediums using the same pigments, but I am primarily concerned with watercolor since it is far more likely to have fading issues.

Hi, Brian!

Having a color known to be fugitive is an excellent way to do this comparison. If Aureolin takes too long to break down, try Alizarin Crimson (PR 83). It's what regularly used as a standard, as most samples should fade within 5 weeks of direct exposure to UV light.

Gigalot
08-28-2014, 02:03 PM
Hi, Brian!

Having a color known to be fugitive is an excellent way to do this comparison. If Aureolin takes too long to break down, try Alizarin Crimson (PR 83). It's what regularly used as a standard, as most samples should fade within 5 weeks of direct exposure to UV light.

I have more interest to test "cadmium yellow hue" and "cadmium red hue". To test all those highly non-toxic, environmental, non- pollutant, non-carcinogenic, non-mutagenic, non-water-forest-sea impactors. How much time our extremely non-toxic yellows and safest reds pigments can stay on sunny beach conditions?
:confused:

kaef
08-30-2014, 07:08 PM
Hello All!
Please pardon my ignorance here, and I am ignorant, but are we absolutely certain that what causes PR106 to darken and PR83 to fade is UV light?
Most of y'all understand chemistry much, much better than I do- and that's not really a compliment. But could there be another element to sunlight that causes these phenomena to occur? Or perhaps what causes Vermillion to darken isn't the same thing that causes Aliz to fade.
I may be oversimplifying here but if it were just a matter of blocking UV rays it seems like these issues could be easily rectified. :confused:
Thanks!
Tom

Mythrill
08-30-2014, 07:38 PM
Hello All!
Please pardon my ignorance here, and I am ignorant, but are we absolutely certain that what causes PR106 to darken and PR83 to fade is UV light?
Most of y'all understand chemistry much, much better than I do- and that's not really a compliment. But could there be another element to sunlight that causes these phenomena to occur? Or perhaps what causes Vermillion to darken isn't the same thing that causes Aliz to fade.


Hi, Tom!

Alizarin Crimson (PR 83) is strongly affected by sunlight. As far as I know, though, it's not reactive to anything in the atmosphere.

Vermillion (PR 106), on the other hand, doesn't actually fade: it becomes deeper and darkens. It also reacts to hydrogen sulphide, which worsens the darkening, which may cause Vermillion to turn completely black!

Different media (acrylics, pastels, gouache, etc) can make the paint act differently, and there are more variables I'm personally not aware of. Does anyone know more about fading and blackening of these two pigments?

Mythrill
08-30-2014, 07:41 PM
I have more interest to test "cadmium yellow hue" and "cadmium red hue". To test all those highly non-toxic, environmental, non- pollutant, non-carcinogenic, non-mutagenic, non-water-forest-sea impactors. How much time our extremely non-toxic yellows and safest reds pigments can stay on sunny beach conditions?
:confused:

Hi, Giga!

I see what you're getting at. We're quickly throwing away cadmium paints and jumping to alternatives, but the data we have about the alternatives is relatively new. We know Azos are less toxic than, say, Chrome Yellow (PY 34 and PY 34:1), but... how less toxic, really? And how less carcinogenic?

kaef
08-30-2014, 08:25 PM
Hi Mythrill!
I'm wondering if PR83- or genuine Madder- fades because of its plant based-ness. In the same way that a leaf you grab off the ground in the fall fades when pressed in a book, if that makes any sense.
As PR106 goes, is there any difference between Mercuric Sulfide and Cinnabar showing that one darkens while the other doesn't?
I'm also curious about how Aliz acts when it is behind UV protectant glass. If it is stabilized then one might expect that the same thing could happen with a generous coat of varnish.
Also, just to clarify, I'm always talking about oil paint. Are Vermillion and Alizarin Crimson even available in acrylic?
Thanks!:thumbsup:
Tom!

Mythrill
08-30-2014, 09:03 PM
Hi Mythrill!
I'm wondering if PR83- or genuine Madder- fades because of its plant based-ness. In the same way that a leaf you grab off the ground in the fall fades when pressed in a book, if that makes any sense.
As PR106 goes, is there any difference between Mercuric Sulfide and Cinnabar showing that one darkens while the other doesn't?
I'm also curious about how Aliz acts when it is behind UV protectant glass. If it is stabilized then one might expect that the same thing could happen with a generous coat of varnish.
Also, just to clarify, I'm always talking about oil paint. Are Vermillion and Alizarin Crimson even available in acrylic?
Thanks!:thumbsup:
Tom!

Hi, Kaef!

Alizarin Crimson (PR 83) is the synthesized version of Madder, usually without purpurin (which gives Madder the "rosy" color). Natural Madder (NR 9), extracted properly, is slightly more lightfast than Alizarin.

UV protection can help delay fading, but not by much. According to what everyone says here, UV varnish protection lasts only around 2-3 years.

As for Vermillion (PR 106) vs Cinnabar, some say Cinnabar is slightly less prone to darkening, but there's no consensus on that. The natural source is probably less pure, and, having less mercury sulphide could be the cause of the lesser darkening.

Some sellers make Alizarin Crimson available in acrylics. I have myself a sample for color-matching studies and lightfastness tests which you can see in this thread: http://www.wetcanvas.com/forums/showthread.php?t=1358601

There's no genuine Vermillion in acrylics, though. The reasoning is that cadmium reds (PR 108) provide a much better red, all with higher chroma and less reactivity. If cadmium reds ever become unavailable, we still have something like Pyrrole Red Light (PR 255). While it does not have the range Cadmiums do, at least it's lightfast and weatherfast, meaning you can use PR 255 for outside painting.

Brian Firth
08-30-2014, 09:19 PM
Here's my test of M. Graham Alizarin Crimson Acrylic. Surprise! It's just as fugitive. :wink2:

1 year of South facing window sunlight exposure.

Brian Firth
08-30-2014, 09:35 PM
And here is my current test of Soluvar varnish which claims to contain UVLS. I used the treacherous Holbein Chinese Red PR188(?) mixed to a light tint with W&N Titanium White PW6 PW4 and applied to Fredrix canvas. I allowed it to dry for about two weeks then applied two good coats of Soluvar Gloss to the bottom half of the swatch. After a few more days I cut the swatch in half and placed it in my trusty south facing window for exposure. The swatch on the right has been exposed for exactly 43 days and is already fading. It would appear that the varnish had not had any effect of protection from the UV fading whatsoever.

I had previously done this experiment with genuine vermilion and got the same results.

Conclusion: UVLS varnish does not appear to offer much, if any protection from uv light.

For future tests I would like to try very heavy coats of the varnish in the 5 to 10 coats range to see if that makes any improvement.

Final note: Avoid Holbien's Chinese Red. it makes Alizarin Crimson look absolutely permanent by comparison!:(

Aspsusa
08-31-2014, 02:24 AM
UV protection can help delay fading, but not by much. According to what everyone says here, UV varnish protection lasts only around 2-3 years.

Two to three years in what conditions? Normal home? Strong gallery lighting? South facing window?

Gigalot
08-31-2014, 09:04 AM
Two to three years in what conditions? Normal home? Strong gallery lighting? South facing window?

It can protect paint from Sun on the beach, but temporary. :D As sunblock cream. Instruction recommends to rub sunblock on skin every two hours to have a good sunburn. :cat: