What is a pigment?
A pigment is a chemical compound that gives your paint its colour. Historically these may have been powders from ground up rocks, or laked dyes derived from plants. The majority of modern pigments are synthetic. There’s a whole history and chemistry lecture to explore in the nature of pigments, but today I just want to provide a quick and dirty low-down on why we care about which pigments are in our paints, and how to tell what they are.
The most obvious point is that the pigment will determine the hue and value of your paint. The pigment also has a big impact on other important behavioural qualities.
- How opaque or transparent the paint will be.
- The tinting strength of the paint.
- The staining power of the paint.
- Whether the paint is granulating, or smooth.
The maker’s specific recipe will also influence these things. The milling process and added fillers, brighteners, humectants and surfactants all play a role, but often the pigment will have the largest impact.
How to find out what pigment is in your paint.
Each pigment compound gets assigned two codes. The Colour Index Constitution Number is a 5 figure number, making it difficult to memorize or recognise.
The Colour Index Generic Name Code is much more intuitive. In watercolour paint this will be in the format P(for pigment) followed by a letter code for the colour family (R for red, or B for blue, Br for brown etc.) then a number up to 3 digits long. For example PR108 is the generic name code assigned to Cadmium Red. Occasionally you might find a N instead of a P. For example the code for Winsor and Newton’s Rose Madder Genuine is NR9.
The majority of artist grade paints will have the generic name codes somewhere on the packaging, although they are not legally required to disclose this information.
Below I’ve included two examples of clear pigment labelling along the side of the paint tube. In this case both paints are made from PY43, yellow iron oxide.
Yellow iron oxide PY43 (natural) or PY42 (synthetic) is an inexpensive, widely available and permanent pigment, so there’d be no reason to use anything else to make yellow ochre, right. Right?
Wrong. As shown in the above image, White Nights yellow ochre is made from a mixture of PY43 and PY154. It also paints out as a significantly lighter colour than either the Daniel Smith or the Winsor and Newton examples. This brings us to the next point:
The marketing colour name may not correspond with the pigment.
Paint manufacturers can give their colours any name they choose, and their marketing gurus will choose names based on what they think will sell. These usually fall into one of three groups:
- Traditional. Generally these are names associated with current pigments such as Cobalt Blue or Cadmium Red. They also include historical colours such as Sepia or Vermillion. If the pigment is currently available (for example Cadmium Red) the paint should either contain the associated pigment, or be labelled as a “hue” paint, but always check to make sure. Sepia is no longer made from cuttlefish ink and may contain a variety of pigments designed to imitate the original red-brown colour.
- Romantic. Colour names that may be either practical or poetic descriptors of how the colour appears or what you might paint with it. Examples might be “Bright Pink”or “Moonglow” or “Undersea Green.” These may be multipigment mixtures. They might be pigments where the generic name is difficult to remember or pronounce, making it less marketable.
- Branding. This is where the company uses their own name as the paint colour descriptor, for example Winsor Red, (PR254 Pyrrole Red) or Blockx Red (also PR254 Pyrrole Red). I don’t really understand why paint makers do this. They usually (not always) stamp their own name on single pigment colours made with reliable modern synthetic organic pigments.
Same pigment, different colour names.
The above image shows examples of three paints with very different names, but the same pigment ingredient. From left to right we have Qor’s Phthatlo Blue Green Shade, Winsor and Newton’s Winsor Blue Green Shade and White Nights’ Bright Blue. In this case I believe Qor’s labelling is the most useful, as the pigment name is PB15 Phthalocyanine blue.
Despite the different names, all three are similar in hue, transparent and staining, with good tinting strength.
Same name, different pigments.
The reverse can and does occur. Take a look at this party pack of Hooker’s greens.
Although all these paints are relatively transparent, there is a lot of variety in the hue and value.
Sometimes I want to match a paint colour from another brand, either because I’m following an instructor who uses a brand I don’t have, or because I’ve run out of a favourite colour and want to pick a similar replacement from the mini mountain of paint I already own.
It is usually a much more reliable to match colours using the pigment code, rather than looking for a colour with the same marketing name.
This also makes it possible to imitate convenience colours you might not have. For example I have a sample of Daniel Smith’s Undersea Green, which is a lovely colour. It is made from PB29 (Ultramarine) PO48 (quinacridone burnt orange) and PY150 (Nickel Azo Yellow) all of which I own as single pigment paints. If I can get the proportions right I could potentially mix a very similar paint.
Hue paints
Another thing to keep an eye on is paints where the name has hue written at the end. These are designed to imitate colours where the genuine pigment is either fugitive, toxic, expensive, or a combination of all three. I’ve also seen hue colours labelled as “tint” or “imit” which is presumably an abbreviation of imitation.
Hue paints are more common in student grade ranges (replacing expensive pigments)but they can be valid in artist grade ranges, for example as a more permanent alternative to the genuine Alizarin Crimson PR83.
How close these imitations are varies wildly, so I’d suggest investigating them on a case by case basis.
For example Aquafine’s Alizarin Crimson (hue) is paler, pinker, and duller than any of the 3 genuine alizarin crimson paints I’ve tried, which were all very similar. On the other hand Aquafine’s Cadmium Red (hue) is a similar colour to a real cadmium red, sitting somewhere between my Winsor and Newton Cadmium Red and my White Nights Cadmium Red Light. It is however more transparent than either of the real cadmium reds, so that’s something to keep in mind.
Get to know your paints
When following an instructor I like to paint with what I already have, which sometimes requires substitutions. Knowing the generic name code for the pigments in my paints allows me to make more informed choices for a close match.
It is also very useful if you run out of a paint, only to find it has been discontinued. You may find the same pigment is still available from a different brand, or under a different marketing name.
What do you think? Do you rely on the marketing names to chose your paint colours, or do you go by pigment codes?
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