Sunday, September 5, 2010

Color index names, what in this paint?

There is a system called the color index. Each pigment has an abbreviation followed by a number. This is usually printed below the colors name on a tube of paint. Often pigment has a name like coral red or organ meats violet given to a proprietary mixture by its manufacturer. A color like cadmium yellow is made out of cadmium yellow ( at least it should be). Colors called hues, like cadmium yellow hue are mixtures made to imitate cadmium yellow out of less expensive pigments. Most student brands contain hues rather that the real pigments. The index number will tell you what those ingredients are. However, I recommend never buying any color that has hue in its name. They are seldom more economical in practice because of their low pigmenting strength. Most artists use single pigment colors, that is when there is a single pigment in the tube, not a mixture of several to obtain a mixture with a certain hue. When you see a color with a romantic name like provincial mauve, that is a mixed color and could have who knows what in it. You can figure it out though, by the little code below its name.

PY= pigment yellow, PG means pigment green, PW means pigment white and so forth. After the alphabetical prefix comes a number suffix. For instance PB29 means ultramarine. The 29 is the notation for ultramarine pigment ( man made ultramarine, that is). There are a number of ways you can look up these numbers. Many color makers publish a list on their website telling you the index number and what the pigment is. Gamblin, for instance does. Often you can enter the index number into Google and find out that way.

The index numbers are handy when you need to know whether what you are using is actually made with pthalocyanine blue rather than ultramarine or cerulean for instance. The index code for pthalocyanine is PB 15 or 16. If your tube of Astral blue is really pthalocyanine rather than ground up astrals, the index number will say PB (pigment blue) and the number 15 or 16 (pthalocyanine). Most of the proprietor named multiple pigment mixes can be as effectively mixed on your palette. There is nothing wrong with them particularly, and you might find some that are useful to you , but you do want to know whats in them.

The RGH paints, that I use, have a nice index chart on their site. Here that is.


Mary Bullock said...

Stape, I think some confusion arises when you state in this post that one should not buy any paint with "hue" in the name but in a previous post, a few days ago, you stated that the "name of the color is the hue".

Nita said...

Stape is right in both cases. The properties of color are Hue(name of a color), Value (light or dark), Intensity (pure or grayed), and Temperature (warm or cool). The ASTM International has assigned the pigment index names and also the standard of calling substitute colors "hues." At one time, some manufacturers called them "tints," but that was even more confusing, since the word indicates a lighter color.
Stape-thanks for posting such a good explanation of index names. I wish more artists would learn this.

Poppy Balser said...

Stape, I enjoy your blog very much. I am a watercolour painter but always find something valuable in each of your posts. (Loved the series on Winslow Homer's watercolours, btw!)

I found the handprint website to be a very useful site for learning about pigments, paints and colour theory. It contains much more than anyone can digest in one sitting. (Much like your blog! Worth returning to often!) Some of the material is watercolour specific but not all of it.

Thanks for all the great information. As someone who never attended art school or had any formal training you are helping to fill a large gap in my knowledge base.

Stapleton Kearns said...

I thought about that as I wrote it. But that is the proper term for the colors. Not to use it would be confusing too.

Stapleton Kearns said...

Thank you for clarifying that.ASTM does get the last word, I guess. I see why Mary finds it confusing.It does make sense as you think about it though, hue means a color and they are a color, just not the real pigment expected to be that color. A dreadful business all around.

Stapleton Kearns said...

Thanks, one of these days I will do a history of watercolor and talk about some of the great watercolor books out there, like John Pike.