Paint Pigments and Lightfastness: A Practical Guide for Artists
What this helps you do
Read material labels and preserve what you used for future reference.
Most artists choose paints by color first and almost everything else second. That is fine when you are sketching, but it can quietly damage the work you sell. Pigments behave very differently over time, and a painting that looks vivid in your studio can shift, fade, or darken on a collector's wall within a decade. Here is how to read pigment labels, what the rating systems actually mean, and how to keep records that protect you and the buyer.
What lightfastness actually means
Lightfastness describes resistance to colour change under light exposure. It is influenced by the colourant, binder, concentration, substrate, and the actual light conditions. A pigment name alone is not enough to predict how every paint formulation will age.
Two rating systems matter in art materials:
- ASTM D4303. The A test method for assessing relative lightfastness of colourants in artists' materials. Check the manufacturer's stated rating and testing information for the particular paint.
- Blue Wool Scale. The A scale used in conservation and industry. Higher numbers indicate greater resistance to fading under the test conditions, but display duration and light level still affect the result.
Many manufacturers also use their own internal scale (such as a star system from one to four). These are usually a translation of ASTM or Blue Wool, but they are not always equivalent across brands. When in doubt, look for the underlying ASTM rating on the tube or the manufacturer's technical sheet.
How to read a tube label
Every artist-grade paint tube includes the information you need, if you know where to look. The four things to find:
- Pigment code. A letter and number combination such as PB29 (ultramarine blue) or PR108 (cadmium red). This identifies the actual chemistry.
- Lightfastness rating. Usually printed near the pigment code, sometimes as a number, sometimes as a star rating.
- Series number. Indicates the price tier, which often correlates with pigment quality and concentration.
- Single pigment or mixture. A tube with a single pigment code is generally cleaner to mix with than a tube with three or four codes.
Pigments to avoid in finished work
Some colours and formulations are more light-sensitive than others. Their suitability depends on the manufacturer's rating, the medium, how the work will be shown, and what you communicate to a buyer. Check the current technical sheet rather than treating a colour name as a universal rule. Common examples to investigate include:
- Alizarin Crimson (PR83). Beloved for its deep transparent red, but a historical colourant with documented light-sensitivity concerns. Products sold under similar names can use different pigments, so check the exact tube and technical sheet.
- Opera Pink (PR122 with fluorescent dye). Fluorescent colourants can be especially light-sensitive. Avoid promises about permanence without product- specific test data.
- Aureolin (PY40). A historical pigment whose behaviour can vary by formulation and conditions. Check current manufacturer data.
- Hansa Yellow Light (PY3). Check the specific manufacturer's lightfastness data and formulation.
- Some daylight fluorescent colours. By design they cannot meet archival standards. Use them deliberately or not at all.
A light-sensitive colour does not determine a work's value. Clear, factual material records and careful display guidance can help a buyer understand what they are acquiring.
Other archival considerations
Lightfastness is the headline issue, but a few other pigment properties affect how a painting ages:
- Tinting strength. How much a pigment dominates a mixture. Phthalos are extreme; earth colours are mild. Tinting strength affects how predictable your mixes are.
- Drying rate. Some pigments can influence drying, but paint film behaviour depends on the whole formulation, layer structure, and environment. Follow the paint maker's guidance for your system.
- Opacity. Important for layering decisions, especially in oil painting where fat over lean rules apply.
- Health and toxicity. Some pigments carry health hazards. Read the label and safety data sheet, avoid eating or drinking in the work area, prevent dust from sanding, and follow local waste rules.
Document the materials in each painting
A painting that lives for fifty years will be examined by conservators, insurers, and buyers who never met you. The most useful thing you can leave them is a clear record of what is actually in the work. At minimum, note:
- The pigments used, by name or pigment code.
- The medium (oil, acrylic, gouache, mixed).
- The ground and support (linen, cotton, panel, paper).
- Any varnish applied, including the type and date.
A line on the back of the painting is a start. A dedicated inventory entry is better, because it survives reframing, lining, and the slow disappearance of pencil from canvas backs. This is part of why consistent inventory records matter beyond the moment of sale.
A simple pigment audit
Once a year, pull every tube out of your studio and record the pigment code and the manufacturer's stated lightfastness rating. If an important colour has limited data or a lower rating than you expect, compare alternatives before using it in work intended for long display.
You do not need to eliminate every less-lightfast colour. You do need to know what you are using, keep the material record, and avoid overstating permanence to buyers.
Sources and further reading
Keep a permanent record of the materials in every painting
Artwork Codex stores medium, support, and notes on each artwork, so collectors and conservators can always trace back what is actually in the work.
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