Test Your Colours!
by Robert Sloan
Colour Chart of my Daniel Smith watercolours
Chart all the watercolours you buy, even if you get the same colour from a new brand. It may not be exactly the same hue as the same name from the first brand.
Even if it says that it uses the same raw pigment by its pigment number, like PB-29 Ultramarine Blue, the exact color can vary by how the manufacturer grinds the pigment, what goes into the binder - gum arabic is usual but also honey and many other gums and substances can go into proprietary binders - and how it's mixed or poured.
In watercolor pans, Yarka has a special process that makes the colour much stronger in their pans by how they're poured, not pressed.
So what I do when I buy any new watercolours is make a chart of all the colours and let it dry, then compare it to the colours in other brands.
Blick Artists' watercolour in Raw Sienna is less reddish than Winsor & Newton's, so I need to add just a touch of Light Red in it to match the W&N colour. But the price of Blick Artists' watercolour is a good deal less for a big 14ml tube than W&N Artists' so I'm better off doing a dab of mixing than using up my 5ml tube that fast on big paintings!
I keep all my charts in the same place in my Moleskine watercolour journal so that they're easy to find, and easy to compare just by paging through.
Thanks Robert! This is more than a tip. It's a great little mini-article which I'd heartily endorse to anyone, beginner or experienced painter alike.