Watercolour paints may or may not be vegan.
Though most ingredients are animal-friendly, the humectant in watercolour paint may be honey (though due to cost, it is most often made from corn syrup). Another ingredient, called the dispersant or wetting agent, is commonly made from ox gall, though synthetic surfactants may be used instead. In addition, the plasticizer is usually made from glycerin, which may be of vegetable or animal origin.
Information gleaned from handprint: how watercolor paints are made
Watercolour paper is likely not vegan if it has been buffered, a process which uses milk. Felt may be used to lift and dry the paper as it is being manufactured. Sheets may be sized with animal gelatin, but in commercial manufacture are more likely to be sized with carboxymethylcellulose, a plant-derived product, or with alkyl ketene dimer, derived from plant or animal fats. Since gelatin is prized as superior sizing, it will usually be mentioned in manufacturers’ descriptions of the paper.
According to this page at www.artpaper.com, wheat starch or methycellulose can be easily used at home to prepare unsized watercolour paper for painting (see under the “Organics” heading).
Animal-friendly companies and products
Holbein Artists’ Watercolor -”Without ox-gall, other animal by-products or other dispersing agents” according to the company website description – excepting the Ivory Black, which is made from charred bones
Cotman Water Colour by Winsor & Newton – excepting Viridian Hue, Burnt Umber and Ivory Black, according to a comment posted here and according to a “vegan information sheet” provided by Winsor & Newton
Shizen Watercolor Papers are reputed to be vegan and at the least are “made from 100% recycled materials using a pollution-free process”
Strathmore papers are reputed to be vegan, however since they are buffered they may or may not involve milk in the processing (to be researched)
Rives Printmaking Paper is supposedly sized with synthetic gelatin, however it is also buffered and may or may not include milk in the processing (to be researched)
Have I missed anything? Please drop me a line and I’ll add or change as need be. vegan dot seeds at gmail dot com.