If you are going to throw the margarine out anyway, it does not hurt to try to make soap out of it. Call it a science experiment and see what it does!Thanks for your replies, everyone. Yes as regards the other additives, I was considering boiling it up first in water to try and clarify it, and then weighing out what's left to calculate the lye. On the other hand maybe it's not worth the bother, but the block of marge keeps looking at me whenever I open the fridge door ....... I didn't like the pastry I made with it.