demographic said:
A mate of mine is currently getting set up making Biodiesel (legally that is) and a by product from the process is fairly large quantities of tallow/animal fat.
Currently he has about a quarter of a metric ton of stinky tallow/animal fat and not much to do with it
Cheers Scott.
To purify animal fat/dirty tallow in to good tallow
1. Put as big a pan as you have on the stove and fill it most of the way with water.
(Too little water and the fat will darken as it separates into Tallow.) Animal fat has a lot of salt, which needs to be removed, so the more water the better.
2. Put the fat/tallow into the water and get the water boiling.
As the fat renders, the tallow will float to the surface of the boiling water. More and more tallow will rise until the water is skinned over with a rain-bow mother of pearl layer.
3. Use a big spoon to skim the layer off, and set this layer aside. Keep skimming till no more tallow rises. This is tallow, good clean tallow
4.When the fats boiled enough that no more tallow rises, throw out the boiling water. Wash the pot and fill it with clean water. Repeat the process with the skimmed tallow. Boil the tallow in the water. Skim and keep skimming. Too much salt left in the tallow and your soap will not solidify. Collect the tallow and keep refrigerated.
Warning: A clear layer of something thick will collect on top of the tallow in the fridge. The clear layer is glycerine. You can mix the glycerine back in when you make soap, or you can skim the glycerine off and use it for other things (like moisturiser or more expensive styles of scented soap)
The instructions for making soap can be found
here