You may remember that I hadn't heard back from Winsor and Newton regarding my questions on cadmium paints. Well, today I received a nicely informative response!
Here was my original question:
I am a newcomer to watercolor painting and now working through some color mixing exercises.
I'm using Cadmium Yellow and read that this is really a mix of two pigments--PO20 Cadmium Orange and PY35 Cadmium Yellow Light. Then I noticed that Cadmium Orange is actually a mix of PY35 Cadmium Yellow Light and PR108 Cadmium Red. How curious, I thought, that Cadmium Orange would contain no Cadmium Orange but that Cadmium Yellow would!
Could you help me understand why this is so? I'm just a beginner so I'm lacking lots of information but I am very curious.
And here is today's response:
Thank you for writing to us. I am sorry about the delay. I needed to contact the lab and I’m afraid your answer was caught in between a chemist’s vacation and my vacation. The reason for both of these mixtures is that Winsor & Newton tries as far as possible to maintain the same colour standards we always have in spite of changes in raw material supply.
When cadmium pigments were first introduced in the nineteenth century the colour range was limited to mid yellow to yellowish orange. The pigments were made by a simple wet precipitation process and had good but not outstanding permanence.
In the early 20th century the yellow pigments were greatly improved in opacity and permanence by calcining them after precipitation and the colour range increased to include paler greener shades which we would now call cadmium lemon or cadmium yellow pale. In the 1930’s the modification of the cadmium sulphide yellows by including selenium in the process extended the cadmium colour range from yellows through oranges to deep reds.
The original cadmium yellows used by Winsor & Newton were of the old non-calcined type and were generally redder than the modern pure yellows. When replacing them it was found that the best match for Cadmium Yellow was achieved by mixing the modern yellow (PY 35) with an orange (P0 20).
The old type Artists Water Colour Cadmium Yellow Deep and Cadmium Orange were a little more difficult to match because they had an unusually reddish masstone and a relatively yellow undertone, and it was found that a better match for these was obtained with a mixture of a PY 35 yellow and a cadmium red PR 108.
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