Greys become purple when using Ultramarine blue
During 2022 I followed a great online painting course in where I (a.o.) really dove into color mixing, especially muting colors to greys. I like it and see how I can enhance some bright parts of my paintings with that. But……after drying lots of the grey tones appear purple, so I end up with purple clouds, purple shadows. I suspect that it has to do with using ultramarine in the mix. I think that that color doesn’t get lighter when drying, or at least less lighter than e.g. burnt sienna or orange.
Does any of you recognise this problem? Do you have a trick to avoid it? I tried to mix more towards brown/warm grey, but that is quite difficult when painting wet in wet, adjusting for the value and the change in hue at the same time.
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The problem is not Ultramarine. Although a warm blue, I use it for most of my greys. They will err on the side of purple if you use reds at the pink end of the spectrum (alizarin, quin red, permanent rose etc.) If you use reds that are more neutral or earthy (cadmium, burnt sienna , light red) then this will be less of a problem. Even if you are using the more pinky reds, or indeed for any red, just mix in a little yellow (raw sienna, yellow ochre) and that will give you a more neutral, less purple grey.