A pure crimson lake contains the colouring matter of the cochineal, known as carmine, precipitated on a base of alumina, but scarlet lakes contain vermilion. A pure crimson lake should dissolve entirely in a solution of caustic soda, yielding a bluish-carmine solution, and it will precipitate out again by carefully neutralising with dilute acid. As a rule, pure crimson lake does not yield colour to alcohol, whereas the aniline so-called lake colours usually tint alcohol very strongly because the colours are but weakly held by the base. The colour of cochineal lake becomes bluer with ammonia and yellower with an acid, but the behaviour of lakes containing aniline colours will vary with the nature of the colour used. Crimson lake, when carefully heated in a porcelain dish, should burn away, leaving a small quantity of a light white ash; a large amount of residue, either white or coloured, shows evidence of adulteration with mineral matter. Crimson lake, being a bad drying pigment, should be ground with boiled oil, if oil is used; but it would be better to apply the lake ground in turps and to varnish over it, or to grind it in a quick-drying varnish.

In any case it is a fugitive colour, fading in bright sunlight very rapidly.