Primer Annulus colour Ink varnish

Anyone know what type of Ink or varnish is used on the primer annulus of British ammunition either a Blue purple or in green. Is it similar to engineer bluing ink and is it to seal and waterproof the primer.

Just read somewhere that it is a varnish, any partcular type, fast drying coloured shelac or just plain varnish.

Yes it has two uses, to seal the primer from water & other things that can lessen it’s sensitivity, and to with come countries products identify the type of load. Green is usually AP in the British code along with a “W” in the headstamp.

The exact formula, good luck finding that as I’m sure every country at different times had different formulas, and I’d bet, no two were alike.