The plural form of bister; multiple varieties or samples of the brownish soot pigment used in art.
From bister + -s (plural marker). Straightforward pluralization of the singular noun referring to multiple quantities or types of bister pigments.
Art supply shops in European cities still sell bister cakes today—artists stack them in trays like ancient paint boxes, and a good quality bister costs less than a coffee but lasts for years!
Complete word intelligence in one call. Free tier — 50 lookups/day.