Lightfast Testing For Artists, How To Window Test Art Supplies, Myths and Understanding Rating Scales.
How to do lightfast testing at home. I'll show you step by step how I do my lightfast tests and describe the basic differences between home tests vs ASTM vs Blue Wool Scale professional testing methods and understanding lightfast rating scales. I'll link to resources outside of this website so you can expand your research, including great resources from big brands (like Golden/Qor), their standards for testing paints, myth busting a variety of topics including the idea that "all colors eventually fade", museum lighting, types of light exposure (artificial light machine vs real sun, weatherfastness, heat and PH issues).
How fast do colors fade? Even indoors? Lightfastness is a controversial topic among artists. Some will tell you it doesn't matter or that colors won't fade indoors (away from direct sunlight). Even experienced artists often assume that a lack of fading in their particular household lighting condition is proof that fugitive colors aren't a problem. In high UV index areas (next to water or southern states/near the equator) nearby window light reaching indoor walls can result in fading of LFIII-IV rated colors within several months to years depending on how well lit your house is. In more intense light, such as against the glass where sunlight is shining through a house window for 3-4 hours each evening, some dyes and fluorescent colors can begin fading in just a few days. The most fugitive colors can start showing signs of fading in just a couple weeks.
Does lightfastness matter? Before I knew better, I had given a painting to my grandparents for Christmas, who then hung on their livingroom wall. Unfortunately this was a well lit room, across from sliding glass doors that received evening sun. One year later there was visible fading in all of the reds I had used in the painting. Personally, I never want to see a painting that I worked hard on discolor or fade away ever again. I like to be confident that artwork I sell is a good value for a collector, or that a heartfelt gift given to a loved one will grace their walls for as long as they live. Fugitive supplies discourage me from putting much effort into art (perhaps even preventing me from potentially creating my best work). I'd like to know that a portrait I painted even for my own wall will remain a beautiful reminder of my family or cherished pet for years after they have passed. Art creation can be important reminders of things that are important to you and beautiful examples of what you're capable of on your creative journey. With those things in mind I take lightfastness into consideration when I determine a products worth. My test results help me determine which art supplies I recommend.
Artists who sell originals destined for long term wall display should avoid fugitive pigments, unless the potential for fading is clearly disclosed to a customer or was done purposefully (such neon/fluorescent colors for UV black light effects). You never know what sort of lighting condition your customer has (such as large windows that let direct sunbeams hit walls from sunrise/set). In general I will focus on avoidable fading, but this may not apply to your medium. In general you can find lightfast options in most mediums such as watercolor, acrylic, oil, pastels and pencils. Artists that work intentionally with fugitive dyes (alcohol inks, copic markers, neon colors etc.) will find that these products are not easily replaced by lightfast pigments.
This page covers the following topics:
1) How to do lightfast testing at home. Easily test your paints (including watercolor, acrylic, oil) and dry coloring media (pencils, pastels). I'll show you how I test my supplies, the importance of masstone vs diluted swatches, PH of paper, water, spacing against window glass etc. I'll also briefly discuss the blue wool scale which I use to better estimate the lighting situation and test duration in my area (northern areas need more time due to lower UV intensity compared to southern states/countries near the equator with stronger sunlight). This is an optional tool for serious artists that want to go above and beyond with their testing. Even if you don't have a south facing window, or live in a northern state you can still do lightfast testing - it just takes more time (minimum 6 to 12 months to clearly see all fugitive LFIII-V colors fade).
2) Understanding lightfast rating scales (LFI-V, BW1-8 or * star ratings). Resources for further research. How DIY home testing by artists compares to ASTM and Blue Wool Scale Methods.
---) Can't I just use UV protection spray or glass frames? Why only light distorting thick layers (resin/epoxy pour can help, but how this may lead to smearing and discoloration problems as well as black light fluorescent blocking traits.
---) Myth: Professional means lightfast. While we're on this topic, let's also address the meaningless of product advertising buzzwords like premium or artist quality.
---) Myth: A product is lightfast because it is labeled lightfast, or worse "fade resistant". The fact of the matter is many brands lie, some are misinformed. Most don't actually test their own products, but rather rely on a pigment source for lightfast ratings (a chemical supplier that gives them a colorant powder to mix with binder to make paint labels an ingredient with a blue wool scale ranking).
---) Why use fugitive supplies? Why fugitive doesn't mean poor quality. Certain effects can't be achieved otherwise.
---) Beware cheap product reviews that say they are just as good as expensive brands. When looking at art supply reviews online many products appear to perform well in practice, but later fade. This should be taken into consideration when evaluating the price of products. While many affordable supplies may be featured in "cheap vs expensive" reviews, where artists demonstrate that they were able to make beautiful art from something that cost less than half the price, they don't usually show the long term durability of the cheap option. As an oversimplification, Crayola or Prang watercolors fade in just a few weeks of window light compared to the lightfast pigments that don't fade even after a year in brands like Van Gogh student watercolor.
---) Myth: All colors eventually fade in direct sunlight. False, or rather, we haven't been alive long enough to see the mountains and canyons fade (we make paint from natural iron oxide pigments including PR102, PY43, PBk11 and PBr7). These are technically superior to LFI/BW8 (it's not common to test for BW9 because it would take too long, if ever, to discover fading issues).
THIS PAGE IS IN PROGRESS.
BELOW = TEMPORARY NOTES CUT AND PASTE FROM OLDER PAGES. I will be editing and combining these notes with new photographs in the future.
HOW MY LIGHTFAST TESTS ARE DONE:
Over the past few years I've gotten much more serious about lightfast testing. I've written a lot about what I've learned over the past decade of testing into this page: Learn about lightfast testing, rating scales and a fugitive pigment list. There are some older test images scattered around this site from pre-2020 tests that do not have diluted ranges. All tests are now being done in both masstone and diluted ranges (pale watered down washes). Several thousand colors are currently being tested alongside a blue wool scale panel. Be aware that the antiquated standard of BWS does not meet my standards, as testing stops too early to detect problem pigments that start fading more aggressively after another couple months.
Pigment powder suppliers / chemical manufacturers, brands and even ASTM (a large, now international, testing standards organization) that do testing have repeatedly missed problem colors due to testing too briefly or not properly diluted. Often colors are only tested for about 3 months (*varies by method, elaborated upon in the PO64 video) which can not predict colors that fade at different rates over time. Some pigments become weaker between 6 to 12 months. Some colors speed up the rate at which they fade over the course of slower, more repetitive combination of vertical window glass focused heat, fluctuating indoor humidity and uv absorption. Some colors are much weaker when very diluted making them much more fragile in practice (how a watercolorist might actually use them in a watered down wash) than initially appeared in an official test for masstone. Some manufacturers may test pigments in a different medium (acrylic/plastic/automotive coatings etc.) that are less comparable to the performance of fine art paints. When relevant and in conflict with established ratings I will note Blue Wool Scale ratings, but otherwise will be mentioning time in a window on test images. This is more simple to report and much more relatable and relevant to artists. A rating number or star system scale distorts info based on comparing your color to fugitive textile dyes, spanning "100 years of museum lighting" (not comparable to home lighting where big windows or living in Florida changes the time-table drastically) or test durations run "until alizarin crimson would fade". All of which means very little to the average artist, yet are common practice for lightfast ratings.
My tests are done in a careful controlled manner to avoid dramatic secondary causes of color changes. They are not allowed to get damp, there's spacers on each strip to avoid paint being directly against the glass. Test strips are not exposed to acidic papers and purified water is used. I test on arches cotton acid-free archival paper with no optical brighteners (won't yellow over time). My control color strip is put away in a room temperature drawer hidden from light/window heat. Older tests completed over the past decade for any brands showing masstone swatches only in their results are currently being redone. These new tests are performed behind window glass intensified SW direct sunlight UV in Florida, similar to how ASTM tests are done (they do this at AZ and FL sites). My tests need to run longer due to vertical windows (not skyward facing boxes that receive more light per day).
The importance of diluted testing (water for watercolor, gouache and any paints you normally add water to such as acrylic). You can dilute oil with oil mediums (or white if you only mix opaques and don't use glazing mediums/oils for transparency). Many pigments fade faster when diluted/watered down (vs being full strength/masstone). This becomes very apparent in white tints (sometimes called pastel colors, meaning pale in this case), where basically the paint is pre-diluted. This means white tints/pastel colors are generally more fugitive than single pigment paints. When a tiny amount of a color that fades easily when diluted into a paint mixture is added to white, the color straight from the tube before even being diluted by the artist becomes more prone to fading than if it was 100% that one color without white.
CAN'T I JUST PUT UV PROTECTOR SPRAY ON MY ART?
You can, but it's not likely to help much. Sadly every test I've done has only resulted in the colors fading slightly less, and in some cases has actually made the color change unexpectedly. UV blocking particles in sprays (like Krylon brand) are not sufficient when applied in thin layers. Thick applications help more by bending the rays of light that hit your artwork. It may buy you some extra buffer time if your art is spending a couple days in a bright room, such as a set duration gallery show near big windows. On average Krylon's UV spray made my colors change about 1 week later than they would have without the spray. I've had a lot of alcohol ink customers tell me that they have had the most success with thick applications of resin (like "art resin" or "ice resin" brands). Golden paint co makes good products, but excess care must be taken not to reactivate watercolor paintings when using thick varnish or gel mediums (you also gain a glossy shine). Instead I recommend painting with lightfast pigments and simply framing them for indoor wall hanging.
DO NOT VARNISH/SEAL UV REACTIVE BLACK LIGHT PAINTS: Thick sealers made to protect from UV will also decrease the glow effect (thick layers will completely block black light effects). In an attempt to protect these paints from fading over time, they lose some special effects. Neon, fluorescents or colors that are impossible to find lightfast replacements for should be stored specifically away from window light (a note to customer's regarding the harm of sunrise/sunset light beams may be sufficient warning). Golden MSA varnishes can help protect day glow neon colors (that look vibrant like highlighter markers in normal day light), if you don't mind losing the black light reactive glow effects.
What about UV glass frames? It's an expensive and hard to find gamble if and to what extent they help. This should be compared to the expense of just buying a nice lightfast paint set if you're not working with neon/fluorescents. Most UV glass has just a thin coat of the UV spray on normal glass. This does not work for long term protection and in some cases picture frame glass actually magnifies the harmful effect of UV rays. The effectiveness of UV blocking glass frames varies greatly by manufacturer. Judging by the fact that most serious applications of UV glass are thick, like dark tinted windows for cars or homes, I would assume that thin clear glass offers little to no protection. Museums quality uv protection options are too expensive for the average artist.
WHY "ARTIST QUALITY" OR "PREMIUM" ON A LABEL IS NOT A GOOD INDICATOR OF QUALITY, VALUE OR LIGHTFASTNESS:
"Artist quality" is a general term for any supplies that company made to be used to make art. It does not mean that it is bargain, student or professional grade. When coupled with the word "premium" it is implied that the company feels they used quality ingredients and it contains a good amount of the main ingredient instead of binders/fillers. Not all products will disclose their ingredients, and some even intentionally try to be misleading. Without pigment code numbers listed (color index ingredient) you should assume the supplies are fugitive and I recommend you do NOT believe any lightfast statements made without testing them yourself. "Liquid watercolors" is a particularly bad label, because almost all of them are actually dye inks (often man-made, bright and thin liquids that stain) and not actually the quality pigments (often thick-powder particles mined from real minerals) found in professional watercolor paints. Dyes frequently (and quickly) fade, and a great many artists have been sad to find that their very expensive "ecoline", "PH Martin Radiant" "Viviva" and "Peerless" color sheets (that are dye-soaked papers that can be rewet with a brush) will often disappear near window light within several weeks to months.
You may see LF (lightfast) ratings written on my swatch cards from rating systems you're unfamiliar with. If it's a star system it will say out of how many total stars (5 of 5 being a perfect rating for Schmincke, 3 of 3 being a perfect rating for Rembrandt, Van Gogh or White Nights). Some brands say a single star means fugitive, yet others have a 0/no star policy for LFIV-V. This gets pretty confusing, so it's best to look up pigment codes in question. ASTM (most common in USA brands) is written LFI (most lightfast) to LFV (least lightfast). Blue Wool Scale is common for most other parts of the world goes the opposite way where lower numbers are bad (BW1 fugtiive to BW8 lightfast). This is further explained on the fugitive pigments list page.
Unfortunately many brands simply copy existing ratings from other companies. That's a huge problem if for example 5 different manufacturers make an Ultramarine Blue color paint, but they all get the raw material from a different supplier - it may not all be the same quality. Yet all of these brands may label it lightfast, because it has been generally proven that Ultramarine Blue is a lightfast pigment. There is also the possibility the company will lie or mistakenly pass along misinformation. I'm unsure if that's the case with Faber Castell in the example below (in reference to Gelatos, a water soluble crayon similar to Neocolor II, from the company best known for pencils like Polychromos and Albrecht Durer watercolor pencils):
I've gotten to the point where I do not trust manufacturer's lightfast ratings at all. One too many labels have said lightfast, just for me to find the colors fading within weeks (looking at you Faber Castell Gelatos and every Prussian paint ever made). All companies say Prussian Blue PB27 is lightfast, because it often reverts any fading that occurs if stored away from light (iron salts bleach in sun, and recharge in shade). Unfortunately this damage can be permanent and besides - no painting should need a nap to be considered lightfast.
Most art and craft supplies simply noted as "fade resistant" (without any proper LF rating or pigment codes) have a very poor standard regarding fading. Fade resistant wording on a label should not be misinterpreted as meaning "lightfast". You often see fade resistant and archival as labels on craft and office supplies (stamp ink pads, office markers etc.). This means they should be PH neutral (not technically acid free, but not acidic enough to cause damage to your paper) and use a modern dye that is stable enough to not immediately fade indoors. Fugitive dyes are often labeled fade resistant because indoors, especially in shut sketchbooks/scrapbooks/notepads/journals they will not fade for many years. On a wall near window light they may fade in as little as a few weeks.
---) Why use fugitive colors?
Why bother getting an art supply that isn't lightfast? While dye-based products are almost always fugitive, the point of these products is to achieve effects not easily obtained by natural pigments. Bright, vibrant, neon, smooth blending in markers and certain special effects (see alcohol ink marbling below) can only be achieved by thin particle man made dyes. In watercolor painting, even respected professionals may use "opera rose", a color containing a fluorescent pink dye that allows botanical artists to closely replicate the color of bright flowers. These are ideally used in situations where you will be scanning your artwork for print reproduction, or for using in a sketchbook/personal use where fading will not be problematic.
Fugitive colors should not be confused with poor quality. Professional quality art supplies can be either lightfast or fugitive (prone to fading). Even pro grade watercolors offer fluorescent opera pink which fade quickly, because there is a lot of demand for bright colors or special effects. Even the highest quality paint manufacturers will offer fluorescent pink made with the same care and quality binders as their other paints. Often, bright dye based colors are brighter, more vibrant, than we can achieve with lightfast pigments. Many companies are supplying colors that people want to use for sketchbooks, indoor crafts and for art that will be photo-copied/scanned for book illustrations, magazines, prints or displaying online. Unfortunately, sometimes artists who want to use these products for art to hang on a wall find out later that all their hard work has faded away. These products should not be judged harshly for their poor lightfast results. They do what they were made to do (be vibrant, unique colors, fit a certain type of use, alcohol ink's rock texture/marbling effects, the ease of smooth gradient blending etc.). Copic markers and Alcohol Inks are good examples of high quality dye based products that fade, but many artists still use them because they provide effects other art supplies can not.
HELPFUL? IF YOU'D LIKE TO HELP KEEP THIS PROJECT GOING:
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Cookie, who oversees all lightfast testing, also hopes you found our research helpful :)
Where do I shop for art supplies? This page contains affiliate links. All product opinions are my own. I am committed to honest reviews showcasing both the pros and cons of each product. I have not received payment from any brand for a review. I only recommend stores I have personally shopped with and had a positive experience. I earn a commission from sales made through this web page's clickable banners or links to Amazon, Scrapbook, Arteza, Jackson's or Blick Art Materials websites.
My favorite American art supply chain store is Dick Blick. They have a massive catalog and competitive prices, with quick shipping options here in the USA.
One of my favorite places to shop for a world-wide selection watercolor paint and brushes is Jackson's. They have affordable shipping to the USA and a lovely selection of items not easily found in American stores.
Amazon USA continues to offer more and more art and craft supplies that can be found no where else. They often have import sets, such as Chinese brands like Paul Rubens, that are not available in the more common art stores. As an Amazon associate, I earn from qualifying purchases.
For craft supplies, such as Altenew, Art Philosophy/Prima Marketing watercolors, Tim Holtz/Ranger alcohol or dye inks, stamp pads, markers etc. I shop at:
Scrapbook.com: Thousands of scrapbooking supplies. HUGE daily discounts!
If you're looking for specific lightfast test results, check out the art supplies by brand list or the pigment database pages.