A crimson that looks magnificent on the palette can become a different colour entirely after years in strong light. Oil paint lightfastness ratings give painters a way to judge that risk before the first brushstroke, but the label is only useful when you understand what it describes: the behaviour of a particular pigment or paint film under defined exposure, not a blanket promise that every passage of a painting will age identically.
For painters making work intended to last, lightfastness is not a minor specification. It belongs alongside hue, tinting strength, transparency, drying rate and handling. It affects which colours earn a permanent place on the palette, which are best reserved for studies, and where a seemingly convenient mixture may introduce an avoidable archival compromise.
Reading oil paint lightfastness ratings
Lightfastness is a measure of a colour's resistance to fading or colour change when exposed to light, particularly the ultraviolet and visible wavelengths present in daylight. Manufacturers commonly express it through a rating system, often based on laboratory exposure tests. A higher rating indicates greater expected resistance to change.
You may encounter systems using Roman numerals, with ASTM I generally denoting excellent lightfastness and ASTM II very good lightfastness. Other makers use stars, letters or their own numerical scales. The symbols are not automatically interchangeable, so read the key supplied by the manufacturer rather than assuming that four stars and ASTM I mean precisely the same thing.
The practical distinction is straightforward. A highly lightfast colour is an appropriate candidate for paintings expected to be displayed, stored and collected over generations. A colour with limited lightfastness may still be beautiful and useful, but it calls for a conscious decision about its role. This is especially relevant for bright pinks, violets, certain lakes and some intense modern hues whose visual appeal can disguise a less durable history.
The pigment is the starting point
The Colour Index pigment code is often more informative than the colour name. Names such as Permanent Rose, Naples Yellow or Sap Green are not universal formulae. Two paints with the same name can contain different pigments, have different opacity and mix differently, while their lightfastness may also differ.
A single-pigment colour makes the question easier to trace. If a paint contains one pigment with excellent lightfastness, its permanence is easier to evaluate than that of a complex convenience mixture. This does not make mixed-pigment colours inferior. Many are exceptionally stable and offer useful handling or colour positions. It simply means that the constituent pigments deserve inspection, particularly where a blend includes a fugitive component.
Pigment-led selection is one reason a full colour chart is more useful than a row of appealing colour names. It allows you to compare pigment composition, transparency, tinting power and permanence before committing to a palette. The most enduring choice is not always the colour with the highest rating, but the one whose properties serve the painting without introducing unnecessary uncertainty.
What a rating can and cannot tell you
A lightfastness rating concerns resistance to light-induced change. It is not a complete measure of permanence. A painting also depends on the quality and preparation of its support, the stability of the ground, sound adhesion between layers, sensible use of mediums and varnishes, and appropriate storage or display.
Nor does lightfastness predict every effect of ageing. Oil paintings may yellow in prolonged darkness, and some of that yellowing can lessen with re-exposure to light. Varnishes can discolour, dirt can accumulate, and an unsuitable medium can alter gloss, flexibility or clarity. These are separate material questions. A lightfast pigment cannot compensate for an unstable painting structure.
The rating also does not mean a colour is invulnerable. Laboratory tests provide a controlled basis for comparison, while real paintings meet very different conditions. Direct sun through glass, a brightly lit studio, museum lighting and a painting kept in a domestic hallway produce different levels of exposure. A thin, pale wash of colour over a white ground may reveal change more readily than the same pigment used densely in a darker mixture.
This is why artists should treat ratings as reliable decision tools, not as permission to disregard working conditions. Good materials and thoughtful display are partners.
Why mixtures deserve particular attention
A mixture is only as permanent as its least stable visible component. If a lightly lightfast red is mixed into a blue-grey shadow, the red may fade and leave the passage cooler or duller than intended. In a floral painting, a fugitive pink glazed over a durable yellow can alter the whole relationship of the petals as the pink recedes.
This matters most in tints, glazes and optical mixtures. White extends a pigment across a larger area of the visible spectrum, which can make slight colour changes easier to see. Transparent glazes depend on their chromatic clarity; if that clarity alters, the underlying structure of the painting can change with it. Dense, dark applications may conceal some change, but should not be treated as a safeguard.
When mixing, consider both the immediate colour match and the future balance of the mixture. A restrained earth palette built from durable ochres, umbers, iron oxides and reliable blacks can be remarkably forgiving. High-chroma passages often demand closer scrutiny because they may rely on pigments chosen for brilliance rather than long-term stability. Neither approach is inherently better. The point is to know what each asks of the painting.
Building a palette with permanence in mind
Start with the colours you use most, rather than trying to memorise every rating available. Identify the pigments behind your principal white, yellows, reds, blues, earths and greens. Then note which colours are indispensable to your practice and which are simply familiar habits.
For a first serious oil palette, it is sensible to make highly lightfast colours the foundation. A stable warm and cool yellow, red and blue, along with earth colours and white, can generate a wide range of convincing mixtures. From there, add specialist colours because they offer a particular temperature, transparency, granularity of mark or mixing behaviour - not merely because their masstone is striking in the tube.
Where a less lightfast pigment offers an effect you genuinely need, use it with intention. It may belong in a sketchbook study, an interior work with controlled light, or a short-lived project where its visual character is central to the idea. For commissioned, exhibited or saleable work, many painters prefer to document unusual materials and choose the most durable equivalent where one exists.
Michael Harding colour information is designed to support this level of choice: examine pigment details alongside the physical character of the paint, rather than treating permanence as an isolated specification. A colour that is excellent on paper may not be the right answer in your own mixtures, and a slightly less convenient substitute may prove far more dependable over time.
A practical way to assess a colour before painting
Before introducing an unfamiliar oil colour into an important work, read its label and chart entry. Look first for the lightfastness rating and pigment code, then establish whether it is a single pigment or a blend. Check opacity and transparency as well, since these affect how any long-term change will appear in the painted layer.
Make a small test strip with the colour neat, tinted with white and mixed with one or two regular palette partners. Record the pigment code and date on the reverse. This will not replace formal accelerated testing, but it develops the habit of observing paint as material rather than as a coloured paste. Over time, your own records become a useful guide to the combinations you trust.
Do not confuse a historical name with historical instability. Some traditional colour names now refer to modern, durable pigments formulated to offer a similar visual position. Equally, a name containing words such as permanent, genuine or hue should prompt you to inspect the actual pigment information, not to make assumptions. The tube tells the more useful story.
Lightfastness and artistic intention
There is no virtue in treating every painting as though it must survive unchanged for centuries, provided the choice is informed. Artists have always worked with materials whose beauty, availability and impermanence were entangled. What has changed is the degree of information available before the work begins.
Use that information to protect the colour relationships that matter most. Select durable pigments for passages whose precise hue carries the structure of the painting, be especially exacting with delicate tints and glazes, and reserve more vulnerable effects for occasions where their expressive value outweighs their risk. A well-chosen palette does not restrict invention; it lets your colour remain recognisably yours after the studio light has changed.