A wall of paint tubes is a glorious vision. Who could resist stepping closer and basking in the shifting frequencies of one chroma melting into another?
But when you pick up a tube of paint, the label is crammed full of data meant to tell you what you need to know about the pigment, but you’ll likely ignore this code unless you know how to read it.
What’s in a color name?
Humans like semantic names like Indian yellow because they’re familiar and not hard to pronounce. Everyone trips over Quinacridone, but at least it tells you what’s in it.
Here’s a tube of Utrecht’s Cadmium red medium pure.
The name tells you the chemical nature of the pigment, but Utrecht’s use of the word pure also specifies that the pigment really is Cadmium and not a hue — a mixture of cheaper pigments intended to approximate Cadmium red medium.
Printed labels can misrepresent the real color of paint
See the way the color is depicted on the label? It’s worth pointing out that the printing process is done with inks that are not colored by pigments, but dyes. The red you see on the label is rendered with a combination of cyan, magenta, yellow and black inks and might not really look like the color of the paint itself.
To see what the paint is going to look like, just unscrew the cap and look at the glob of paint trapped in it. Sometimes there will be a significant difference.
The Golden label is black and white except for this swatch of real paint smeared across the three black lines. You don’t need to unscrew the cap on this one, the paint swatch is there to show you what it really looks like and it also shows you how transparent this pigment is.
Furthermore, the swatch is brushed on in such a way that we can see the mass tone (apparent in the thicker areas of paint at the top and bottom of the stroke) as well as the undertone (in the thin part of the stroke.)
Another thing you might notice is the series number, and this indicates where the pigment falls in price range. Ever gotten to the register and said, “Holy shit! Why is Cadmium red four times the price of Phthalo blue?”
Well, it’s because some pigments have to go through more complex and expensive manufacturing processes before they’re suitable for use in paints and plastics and such.
Finding the pigment index number and what it means
In the photo of Golden’s label above, PR is the abbreviation of Pigment Red and 206 is the index number. All the red pigments you use will be prefixed by PR and have a different index number. This is important because, even though PR206 is unlikely to be referred to by a name other than Quinacridone Burnt Orange, some pigments have different names depending on the manufacturer.
This information is located in different areas by manufacturer, but if it’s an artist grade paint, it will be there. If it isn’t, the paint’s quality is probably not suitable for use in your work.
All artist pigments are catalogued in an index grouped by hue and numerical assignments. The index is maintained and published by the Society of Dyers and Colourists (SDC) and American Association of Textile Chemists and Colorists (AATCC). They require a subscription to access their index but you can find a free one here.
Prussian blue, for example, is sometimes referred to as Turnbull’s blue, Antwerp blue, or Parisian blue. But if the label says it’s PB27 and you’re familiar with its working properties, the different names won’t throw you.
Lightfastness and tint strength
Most of the time you’ll find a lightfastness rating along with the pigment index number and it will be a Roman numeral between I-V. Lightfastness refers to how well a pigment stands up to ultraviolet light.
A rating of I is best — you can expect the hue not to change with a reasonable amount of light exposure — and V is … well, terrible. As in, throw that shit away. If you really want to be sure your work will look the same many years later, stick with II at minimum (and only if you’re going to use a UV protectant.) Colors that fade are known as fugitive colors.
Look at how much information Golden’s label has. The scale is nice because you won’t have to try to visualize percentages or other numerical representations.
Most of this stuff is self-explanatory, except for a couple of things. Low tinting to high-tinting. Tint strength is a measure of a pigment’s power to influence a mix. Pigments with high tint strengths can overpower others, so a good rule of thumb is to add those in small amounts to a larger quantity of the other parent color.
What is ASTM and what does it mean for a manufacturer to be compliant?
ASTM International is a global organization that develops and publishes standards for lots of industries and products. With respect to paint, those standards are mainly concerned with health and safety.
Art supplies intended for individual use only must feature a precautionary label listing any ingredients that a board-certified toxicologist feels could have adverse health effects on the user. Labeling should take into account any foreseeable forms of use or misuse. Mark Heidelberger. Quote taken from Ourpasttimes.com
You may have heard that acrylic paint is non-toxic. It is and it isn’t. Most pigments are non-toxic. Others, like cadmium, are harmful if they are ingested or inhaled. Pigment particles are too big to be absorbed through the skin unless you have abrasions.
After the binder (the fluid component of paint the pigment particles are suspended in) dries, the pigment particles are trapped. There is no reason to be concerned about inhalation or absorption at this point. However, there are some that carry warnings against spray application, as they can be inhaled and potentially cause health problems.
What to look for in an acrylic dispersion
Dispersion (or emulsion) just means there are these non-soluble pigment particles and they’re suspended in the binder (acrylic polymers) in such a way that they’re pretty evenly spaced apart instead of sinking to the bottom or clumping together.
You won’t find this on every brand of paint, but Golden’s declaration that their polymer dispersion is 100% acrylic is notable because acrylic polymers will not yellow as the paint ages. Some companies will use an acrylic-styrene copolymer, but styrene tends to yellow slightly over time, influencing the color.
I hope this helps clear some things up. If I’ve left anything out or been unclear about something, feel free to let me know in the comments.