When I bake an Irish soda bread I need to add among other things a bit of white powder called 'cream of tartar'. Last of today's definitions for tartar is:
4. A reddish deposit on the sides of wine casks.

Is the reddish deposit the same stuff (bleeched) as the white powder I use which is known to me as also as winestone acid? Of course ICLIU but that is work and not much of an exchange.