I have an ashery, a soap workshop, and a stockpile that only accepts lye (and barrels), all next to each other. The stockpile contains barrels, which each contain a bucket of lye. The soap makers refuse to use the lye in the barrels in the stockpile, but they can use the lye in the asheries (i.e. while it's still in the workshop and hasn't been put in a barrel yet).

It's similar to the old bug 0004969, though in that bug discussion it's implied that lye in wood barrels is useable, and it's not useable for me.