Acrylics and Fading

[Vaitalla]

Heya all!

 

Reaper paint questions that come via email usually get forwarded to me, and yesterday I got a very good one about acrylic paints and fading. The customer was very into Pro Paints but his friends were telling him to switch to enamels because "acrylic paints fade". Well, like everyone else I'd heard that acrylics fade but that enamels yellow...I did a bit of research and thought I would post my responses to him here, just as an educational aid for anyone who wants to learn some stuff about how your paint ages.

 

My first response:

 

"Hmmm. The very short answer to this is that yes, acrylic latex paints are vulnerable to fading. The good news: unless you're leaving 'em in direct sunlight or a lot of indirect sunlight, chances are you won't notice a fading effect for a long, long time--years, if not decades (I give an example of one of my own minis, below). The flip side which your friends aren't telling you is that enamels have their own issues--if they are using water-based enamels, they can fade just like acrylics. If they are using oil-based enamels, those are prone to their own aging curse: yellowing.

 

Now for the longer explanation...

 

First off, enamels are merely paints which dry to a hard, usually shiny surface. The ones used in model-painting are usually oil-based resin instead of water-based resin, but these days there are plenty of acrylic enamels (Reaper even uses one in its Brush-On Sealer and its inks), so the distinctions are a lot muddier. The pigments for both are generally based on the same chemicals and both can be vulnerable to deterioration, though in different ways as outlined above.

 

In water-based acrylics the presence of UV (direct or indirect sunlight) will put a model at risk for the fading effect (so if you display your miniatures, doing so in a room without a lot of sunlight coming in they'll be a lot safer). It's worth mentioning that it's *prolonged* exposure to UV rays that does it, so leaving a miniature on a windowsill or in your car on a sunny day isn't going to cause discernible fading (I know because I just did that over the weekend!). Fading is usually actually caused by the deterioration or crystallization of the base (the polymer, be it resin, acrylic, latex, or vinyl) as it absorbs UV. It can also be caused by the absorption of moisture or pollutants (acrylic latex is porous). An excellent site which outlines this is the Mural Conservancy of L.A. website. They also state that color can be restored via a light application of certain solvents, but as I've never had a mini fade I've never put this to the test!

 

Oil-based enamels aren't prone to the foggy effect perceived as fading, but all of them yellow over time, so really it's a choice of evils. I have read on some paint companies' sites that enamels will yellow with age even without exposure to UV (one site which says that is one of the companies which works with Home Depot, Glidden). This can be vouched for on pretty much any miniature-painting forum; many artists have stopped using spray sealers such as Testor's Dullcote, citing yellowing issues over time.

 

Mostly my lack of concern re: fading and acrylics comes from my own experience. I have a miniature I painted six years ago for a painting competition which I still own; it's been sitting on my desk a few feet from one window or another for about a third of that time and the rest it's been in a storage box, away from light. It looks exactly the same as the day I painted it (I have pics from six years back to compare) and I would expect it will still look that way ten or twenty years from now as long as I don't leave it where it can get a lot of direct light! The risk of fading is, in my mind, more than balanced by the ease of use, cleanup, and the lack of toxicity of Reaper paints and many other hobby acrylics lines. :)

 

A little more info:

 

1. Red and yellow are usually the most vulnerable pigments to UV exposure.

2. Dyes and tints are much more sensitive to UV than normal pigments, so inks (which are dyes) are very vulnerable to the fading effect (unless they are of archival quality, of which I only know of one--so-called "India Ink").

 

If you have any other questions I would be glad to put my knowledge base to work to answer them. :) Really it is every artist's own choice whether the possibility of fading is really a concern and most world-class painters I know use acrylics these days. If fading was really a problem with acrylics I seriously doubt that those artists would be doing so--they'd be shelling out the big bucks for color fast UV tolerant archival quality oil paints, or something! :D

 

Let me know if this answered your question or if you would like more information. :)

 

--Anne Foerster

Reaper Miniatures, Inc.

Lead Staff Painter, Paint Line Designer"

[Vaitalla]

The customer then responded with a question regarding sealers and yellowing, to which I replied the following:

 

"Short answer: the only spray you can get that will not yellow over time (and even then, all they know is that it hasn't yellowed *so far*...) is an archival quality spray. Art companies such as Golden sell them; they have UV inhibitors to prevent the yellowing effect. They are not cheap ($17.50 per spray can is what I found in a quick online search).

 

Long answer: Both Future and Dullcote have a record of yellowing over time. By "over time" though, you're talking anywhere from five years (it was in a display case which received indirect sunlight) to over twenty years (models were kept in a case in a room with no windows or in a storage case for much of the time). You'll also find people who claim that they don't yellow (I suspect because it might be well over a decade before they do..they just haven't yellowed YET!). The model I mentioned that I still own was hit with about sixteen layers of Dullcote and I have seen no yellowing (and as the skin on its head is a pale lilac and white, I would definately notice!). But it's been kept away from light for the majority of the time and it's only been six years; I would expect, if I started exposing it to more light, that in another ten years I may see some yellowing. Another example, our CEO here at Reaper has models in his office that he painted twenty years back. About 75% of the time since they have been in display cases with no access to indirect or direct light; for the last five years they have been exposed to indirect light in his office. They're dusty, but not faded at all.

 

So really, it comes down to how long you expect your work to last. I did a little more research for you and in the official Guild Handbook for scientific illustrators they talk about deterioration of various mediums, including acrylic paint. They raise the point that since acrylics have only been around since the 1950's, there is no conclusive evidence about how long they can last; many acrylic paintings which have been kept away from humidity and light look as good as the day they were first painted. When it comes down to it, your work is art of a sort, and your clients (assuming you are selling your pieces) are responsible for preserving that art once it has left your hands. Really, the best you can do is use high-quality materials and educate yourself and your clients about the best way to care for the pieces. :) "

 

Anyhoo, hope this was interesting to at least somebody...I thought it was, and thought I would share!

 

--Anne

[vutpakdi]

Interesting stuff: thanks!

 

By the way, back in late April, I started my own yellowing test. I currently have 8-9 spectral minions that I primed and painted Pure White (with an airbrush). To all but one, I applied a coat of varnish from my set of varnishes (Dullcote, Krylon UV Resistant Matte, Reaper MSP Brush On Sealer, Liquitex Matte Varnish, Lascaux UV Matte). About 5 are sitting on a window sill that gets 2-3 hours of direct sunlight and bright indirect light otherwise and 3-4 (duplicates of some of the ones on the sill with a control with no varnish) are in a display case that gets no direct light, dim indirect light, and relatively dim fluorescent bulb light.

 

I'm curious to see how long it will take to see some difference (if any) in color.

 

Ron

[Vaitalla]

Awesome experiment! Please let us know how it goes! The hobby forums I was reading on the subject indicated that it took years for yellowing to show up, so I'd be very interested to know if any of your experiments yellow faster.

 

--Anne

 

Interesting stuff: thanks!

 

By the way, back in late April, I started my own yellowing test. I currently have 8-9 spectral minions that I primed and painted Pure White (with an airbrush). To all but one, I applied a coat of varnish from my set of varnishes (Dullcote, Krylon UV Resistant Matte, Reaper MSP Brush On Sealer, Liquitex Matte Varnish, Lascaux UV Matte). About 5 are sitting on a window sill that gets 2-3 hours of direct sunlight and bright indirect light otherwise and 3-4 (duplicates of some of the ones on the sill with a control with no varnish) are in a display case that gets no direct light, dim indirect light, and relatively dim fluorescent bulb light.

 

I'm curious to see how long it will take to see some difference (if any) in color.

 

Ron

[Vaitalla]

Another interesting tidbit from the handbook of scientific illustrators: To test your acrylics for relative light fastness (resistance to fading), thin them way down and look for separation (using a magnifying glass as necessary). If you have a "control" paint known to be stable, thin that down as well and mix the two together. Any separation (and the degree thereof) when thinned indicates a paint is more vulnerable to fading/fogging/aging because the binders are not supporting the pigment mix as they should.

 

Very interesting stuff!

 

--Anne

[Joe Kutz]

Fading Paints: There is one big thing which wasn't touched upon with this...the nature of the pigment.

 

Most hobby paints which are water based are also made of organic pigments for various safety related issues. All organic pigments will fade due to the break down of the organic pigment into its constituent parts. Depending on the pigment and the environmental conditions - this can take a matter of months to a matter of decades (months generally will only apply to paints exposed to the full force of the elements).

 

Inorganic pigments can still become clouded due to an oxidizing process of the actual binders used as well as - however the pigments themselves are normally very, very stable. The down side is that almost all of the inorganic pigments are known to cause cancer...especially if you live in California or the EU (cadmium, lead, arsenic, chromium...). Any paint which is sold under the ASTM...forget the standard off the top of my head - are supposed to be safe enough for kids to do jello shots with, or something along those lines. Short of it though is that they almost all use the kinder, gentler pigments.

 

When it comes to artists paints though, you get to ignore much of the problems with safety. Adults are allowed to make the choice in the US still to use some of those really bright cancer causing reds and greens (not so much in the EU anymore). Many enamel hobby paints also will use the inorganic pigments too - they lost the safety rating with the solvents...might as well include the cadmium red as well...so although I doubt they knew quite why it was they thought enamels were better, in certain cases....with certain colors....they might have a more lightfast red.

 

When you purchase pigments directly, they normally carry a lightfastness or permanence rating. This is a measure of how much light (primarily UV) the pigment can be exposed to before it is no longer true. While most bottled paints do not provide this information on their bottles - you could probably have them procure it through their pigment providers and pass it along.

____________

 

Issues with the binder...pretty much agree across the board other than everything is local when it comes to corrosion (which is what is happening both with the binder in the paint and the clear coat). Areas like LA which have more airborne free radicals will have a much faster and more dramatic impact on the binder than areas like Iowa. In many cases you will simply have the airborne chemicals binding superficially with the surface of the paint, providing a thin yellowish coating. These can be cleaned up with a mild solvent, by dissolving the surface and taking those chemicals away with it (if you have ever watched a documentary on art and see someone in the background rubbing away at a painting with a q-tip...most likely this is what they are doing). Over a longer period of time though, it will also have a break down of the binder due to light (again, primarily UV). How much time? Again, it will depend. I've got a half dozen samples of different binders in an oxygen rich chamber with UV bulbs a few inches away from their surfaces...going on around 6 months now running 24/7. The only one which has begun to degrade for certain is a vinyl ester base. The others may have started...though I look in too often to notice for certain. When it hits the one year mark, I will open up the case and compare them to the original photos as well as the unclear coated standard.

 

Beyond the existence of external environmental pollutants, you also have internal issues to deal with. Fryers in the kitchen, incense and candles as well as smoking all release a variety of chemicals which are very happy to bind with the clear coats and cause all kinds of havoc.

 

Normally you won't notice the fading or yellowing process - it is slow and gradual...not instantaneous. When the eye sees a slow change, it doesn't register it as out of place. However if you were to take a picture of the figure, and then come back in 10 years and compare the two...it becomes more evident.

 

One of my Spyders has an acrylic rear window (UV stablized even) and after about 7 years I could no longer see out of it due to the oxidizing - some of the older ones that I have are so oxidized that you can not even see shadows through them anymore. However, being a window on a car - they usually get exposed to the full force of the elements (as well as exhaust and other chemicals).

 

I currently have 8-9 spectral minions that I primed and painted Pure White (with an airbrush).

 

Unfortunately, the pure white is going to effect your outcome. The vinyl ester right now is taking on a skim milk look. Over white, I wouldn't even notice it. However each substrate I used is coated half in lead white and half in carbon black. The carbon black is now grey...but the white still looks as white as ever. My understanding of the oxidizing process does lead me to believe that eventually it will in fact turn yellow...however it usually hazes first before going yellow.

[PaintByNumbers]

Joe has waaaaay too much time on his hands, and too much cool lab equipment.

 

There are ASTM standard tests for fading & yellowing used for architectural paints which could be performed on hobby paints as well.

[Joe Kutz]

Retire a half dozen times from a half dozen different technical fields and you will end up with a lot of time and a lot of toys. Toss in a few DRMO auctions from DoD labs - and you get fun stuff like polarizing microscopes and centrifuges. Right now I am still trying to get a handle on that whole retirement thing though. I seem to still be doing too much stuff compared to the old farts that hang out down at the Legion hall when I stop by for lunch.

 

The test that I am currently running is based on the ASTM tests for automotive clear coats as it was the one which seemed to best suit the medium in question (clear coats ), however I have had to make a few changes in the setup due to certain limitations on my part. Took a while in the shop to build the test chamber and figure out how to get a long term control of the environment - but so far so good.

 

For lightfastness of the actual paint colors take a look at ASTM D5398-97. That applies to artist's paints and pigments as well as prescribes a number of tests which are actually fairly simple to perform (compared to many other ASTM tests).