If you work with paints you’re going to find this term everywhere: lightfastness. What does it mean?
Lightfast colors are colors that have a high resistance to fading when exposed to light. Each pigment is assigned a certain level of lightfastness. Depending on the rating system, the lower this level, the more it’s fade resistant. Knowing your art medium’s lightfastness rating is important for several reasons.
Keep reading to find out everything you need to know about this special classification.
Lightfast colores explained
Lightfastness has everything to do with pigments. That’s why artists run into this term all the time. Acrylics, pencils, watercolors and pretty much any colored art supply exist out of pigments + binders.
When a color is exposed to (sun)light, its ultraviolet radiation that is given off will fade or bleach the pigment over time. The main parts that determine lightfastness include the pigment’s stability and resilience. Pigments with strong chemical bonds are less likely to break down when exposed to light.
This means that there are pigments that are stronger (have a higher lightfastness rating) than others.
Lightfastness scale explained
When you buy paints they are assigned a lightfastness rating which can vary from highly lightfast to barely lightfast.
A common rating system involves a numerical scale, often ranging from I to IV. A rating of I is typically given to extremely lightfast pigments, while a rating of IV or V indicates less lightfastness.
- Lightfastness I:
- Excellent Lightfastness
- Lightfastness II:
- Very Good Lightfastness
- Lightfastness III:
- Fair Lightfastness
- Lightfastness lV:
- Poor Lightfastness
- Lightfastness V
- Very Poor Lightfastness
Another way of indicating lightfastness is by using ”+” signs.
Fun fact: The color above is not red, but it’s magenta. If you’re interested in why some use magenta instead of red I advise you to read my complete free color theory guide for beginners!
Is there an international rating system to determine lightfastness?
Technically there isn’t a universal rating but there are standards most companies abide by. A lot of brands use the ASTM rating. ASTM, American Society of Testing and Materials, developed methods of testing lightfastness. There are different ASTM standards.
Brands will tell you what standard they use. For example, Winsor and Newton use the D4303 standard.
There are 4 lightfastness tests:
- A- exposure to natural daylight filtered through glass
- B- exposure to irradiance from daylight fluorescent lamps
- C- exposure in xenon-arc irradiance simulating daylight filtered
through glass - D- exposure to irradiance from cool white fluorescent lamps and
soda-lime glass filtered fluorescent UV sunlamps.
I highly recommend reading this PFD article if you want to dive deeper into how ASTM handles these tests.
Additional information about the performance of your colors
In combination with lightfastness ratings, paints often have two additional ratings as well: permanence and coverage.
Permanence covers lightfastness and also film and chemical stability. It is rated:
- AA
- Extremely permanent
- A
- Permanent
- B
- Moderately permanent
The following symbols show the transparency or opaqueness of a color:
How companies show their rating of lightfastness
This is how the popular brand Arteza shows its colors lightfastness:
Why is lightfastness so important to artists?
Knowing how your paints will behave in the future is important for several reasons. Here’s why lightfastness is important:
- The level of lightfastness determines the ability to sell your artwork
- How long will the artwork keep its vibrant colors?
- Instructions you give your buyers
- Can the artwork be hung near a window?
- Does the artwork have to be framed in UV-resistant glass?
- Do you use student of artist grades paints?
- Student-grade paints have a lower lightfastness rating than artist-grade paints
- The price of the paints
- This will also influence the price of your artwork
1. Do you want to sell your work?
If you want to sell your artwork you should work with pigments that have a high lightfastness rating. Why? Well, because you want your buyers to enjoy your work for years to come.
What if they buy it now, and after 2/3 years your work is completely faded? Not only is this such a waste of your talents, the buyer paid big bucks for it!
Even when you are creating artwork for yourself, you want to look at it later in life. If after a while the colors are faded it is such a bummer.
2. Advice your buyers properly
You need to know the lightfastness so you can advise your buyers if they can place the artwork in full light or near direct sunlight. You might want to advise them to use a UV-resistant frame.
3. Student grade vs artist grade
It seems like a high lightfastness level is better. But that’s not necessarily true. You just need the right circumstances. For example, when you are a beginner artist, or if you’re just doing some ideation or sketching you don’t want to use your expensive paints.
A nice option is to go for student-grade paints. These paints aren’t as lightfast, but it isn’t necessary. They are just to work out your idea!
4. Price of your paints
Paints that have high lightfastness cost more. This means that your budget goes up, and if you sell, you need to calculate those costs into the price of your artwork.
How they test lightfastness
So this is how lightfastness is tested:
- Sample Preparation
- To begin, small samples of the pigments or materials are prepared. These samples are often applied to substrates, like paper or canvas, replicating how they would be used in an artwork.
- Exposure to Light
- The samples are then exposed to different light sources, which can include natural sunlight or controlled artificial light that simulates natural light conditions. Exposure times can range from several hours to several months, depending on the desired test duration.
- Control Samples
- Control samples are equally important. These are kept in the dark to serve as a reference point. By comparing the exposed samples to the control samples, testers can assess how much the colors have changed.
- Regular Assessment
- During the testing period, regular assessments are made to observe any color changes. This involves visual inspection as well as measuring instruments like spectrophotometers, which can precisely quantify color shifts.
- Rating System
- To provide a clear lightfastness rating, testers compare the exposed samples to a set of established standards or scales. Common rating systems include the Blue Wool Scale or a numerical scale. A high rating indicates strong lightfastness, while a lower rating suggests fading over time.
- Repeating the Test
- To ensure the accuracy of the results, tests are often repeated with the same materials under the same conditions. Consistency in results is essential for reliability.
- Environmental Factors
- Testers may also consider environmental factors such as humidity and temperature, as these can influence how pigments react to light.
Of course, all companies may have different testing methods.
List of lightfast colors
Here is a list of colors that are considered lightfast:
- Titanium White (PW6)
- Zinc White (PW4)
- Cadmium Red (PR108)
- Cadmium Yellow (PY35)
- Cadmium Orange (PO20)
- Cadmium Green (PG7)
- Cobalt Blue (PB28)
- Ultramarine Blue (PB29)
- Phthalo Blue (PB15)
- Phthalo Green (PG7)
- Raw Umber (PBr7)
- Burnt Umber (PBr7)
- Raw Sienna (PBr7)
- Burnt Sienna (PBr7)
- Yellow Ochre (PY43)
Keep in mind that lightfastness can vary between brands and specific products, so it’s always a good idea to check the manufacturer’s ratings for the specific paint or medium you plan to use.
List of colors with a low lightfastness rating
Here’s a list of colors that are generally considered to have very low lightfastness:
- Alizarin Crimson (PR83)
- Mauve (PV23)
- Rose Madder (PV19)
- Gamboge (PY150)
- Quinacridone Magenta (PR122)
- Hooker’s Green (PG7)
- Prussian Blue (PB27)
- Indian Yellow (PY139)
- Indigo (PB66)
- Aureolin (PY40)
- Cobalt Violet (PV49)
- Naples Yellow (PY41)
- Opera Rose (PV19)
- Tyrian Purple (PR3)
- Neutral Tint (PW6, PBk6)
Keep in mind that lightfastness can vary between brands and specific products, so it’s always a good idea to check the manufacturer’s ratings for the specific paint or medium you plan to use.
Test your own paints’ lightfastness
This is a fun little experiment you can do yourself, or with your kids!
- Make a rectangular swatch of all of the colors you want to test
- Let them completely dry
- Cover half of each swatch with a piece of paper. Make sure no light is getting through.
- For accurate results, try doing this on the same paper you usually work with
- Write down the date
- Tape this piece of paper to your window with the colors facing the window. Preferably an area the sun directly hits.
- Wait
- Depending on how long you want to test. I should wait at least a month or 3
- After a certain period of time, take off the swatch sheet and the pieces of paper and inspect underneath.
Look at which colors are faded the most. Are there some unexpected results?
Feel free to share your results in the comments down below because I’m super curious! Please mention the brand, colors, and how long the experiment took.
I hope you liked this nifty little piece of information about lightfastness. Just something you need to know :)
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See you next week!
♡ Laura
