White is a really important color in gouache, and I defaulted to Titanium White until I started reading some interesting opinions online about Zinc White. It seems that Titanium White is more opaque and better for highlights and stars and things, but Zinc White is supposed to be a better mixing colors – to make nicer pastels.
So I got myself a tube of Zinc White gouache and tested out pastels made from Titanium vs Zinc with all my gouache colors.
Conclusion: I don’t see much difference!
The entries in the Titanium White column are maybe a bit more chalky and cooler-toned, and the Zinc White mixes are maybe slightly brighter… but it’s so subtle, and could be influenced by different amounts of white in the mix, etc. I don’t really think it’s worth the mental effort of distinguishing between two different whites.
In the top row, I also compared my home mixes with commercial mixes; Holbein Brilliant Pink is a mix of PR209 and Titanium White, and I think my own mixes of any white with M. Graham Quin Red (PR209) match the color well. Holbein Turquoise Green is a mix of PG7 and Titanium White, and tbh both my mixes with M. Graham PG7 felt a bit flat in comparison, but maybe I used too much white, or Holbein’s PG7 is more yellow-tinted, or something.