Science of Watercolor

[Sharon Nolfi]

I’m starting this topic for those who are interested in the more geeky aspects of our paint.

For example, I want to know how one pigment (in this case PB29) can produce varying hues, not only between brands, but within brands. Da Vinci makes 4 Ultramarines: Ultramarine, French Ultramarine, Ultramarine Red Shade, and Ultramarine Green shade. The last 2 I had never encountered before receiving the Green Shade in a Da Vinci Tin.

Ultramarine was originally made from lapis lazuli, and Renaissance artists reserved this rare pigment for the garments of the Virgin Mary. Today, Ultramarine is synthetic. But why so many variations?

[Anonymous]

It is a puzzle. Another puzzle is transparent oxide brown, which is just the same pigment as brown ochre?

[Thomas Blanchard]

Check out Handprint for info on PB29  http://www.handprint.com/HP/WCL/waterfs.html  
scroll to PB29 sodium aluminum sulfosilicate (1828)

 

Basically how I understand it is different paint shades can be made from the same pigment numbers by the way the pigment is ground and the amount of pigment used.  These also make a paint more transparent or opaque.

PBr7 is the single pigment used to make both Burnt Umber and  Burnt Sienna.  Very different colors!  🙂  It is a science for sure!

[Anonymous]

Or alchemy Thomas

[Sandra Strait]

As Thomas said, differences come from the way the pigment is ground and the amount used.  Some pigments are burnt to make a difference, as with raw sienna burnt to make burnt sienna.  I believe some minerals can differ according to where in the world they are mined.

[Sharon Nolfi]

Thanks, Thomas! Has anyone encountered Ultramarine Green Shade and Ultramarine Red shade from a manufacturer other than Da Vinci?

[Sandra Strait]

Winsor & Newton has an Ultramarine Green Shade and if I understand correctly, French Ultramarine is a red shade of Ultramarine. I think there are other names for both the green and red shades.  I’m not sure if they reflect a different amount of the shading or are just marketing devices.

[Jennifer McLean]

I think it’s cool how they make on iteration of a color granulating and the same shade, not. Thank god for that as I usually shy away from granulation unless needed like in painting rocks. I know that sometimes they find, as Sandra suggested, an unusual outcropping somewhere in the world that grinds down differently, like the newest player out there, sapphire phthalo blue. It IS different and that subtlety, for me, makes it even more beautiful phthalo is one of my favorite blues and when I picked up the limited edition phthalo sapphire from W&N I was hooked. Now Schmincke has made that color too. Hopefully they won’t run out, I’ve heard they can just run out of a supply.

[Sandra Strait]

Most of the pigments used in paint come from the beauty and automotive industries.  If they stop using a pigment then it is usually discontinued in the art world as well.  That’s what happened with Quinacridone Gold.

[Sharon Nolfi]

Thanks to all who have contributed to this discussion so far.

[Author]

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