Loaf mould - think of how high and wide you want it to be, for the bars you want to make, then think of how much you generally make when you make a batch. Then go here
http://www.soapmakingforum.com/showthread.php?t=2909 for some calculations.
You can either make the mould to the size that you want and then adjust your recipe to fit it, or take the batch size and work out the dimensions based on that.
Personally, I wanted soaps that were 8cm wide, 5 cm high and a batch of around 1kg but using TWO moulds. So I could then work out -
500 / 0.7 / 8 / 5 = 17.8
oils / 0.7 for metric / width / height = length
But then as 17.8 cm is an odd length, I made it up to 20cm so I can make 2cm deep bars and get 8 bars + 2 ends and adjusted my recipe using -
20 * 8 * 5 * 0.7 = 560grams!
Now it is important to note that this is the INTERNAL space of the mould. You then need to look at the design of what you make so that the internal space matches this. So if your wood is 2cm thick, you need to allow for that so that the wood marries up properly. If you just cut your sides to be 20cm * 5 cm and your base at 20cm * 8 cms, you'll find that you can't fix it together as in the pictures from the link. See there how the sides come up to meet the end piece and that all of it sits on the base? The base size needs to allow for that if you want to make it this way.
Personally, making a hinged mould, I would NOT have the sides resting on the base - when you fold it outwards, the edge can damage the soaps. Better to make the sides higher and put the base between them, with a few feet on the base so that the sides can still unfold.
Good luck! I can't wait to make some more moulds myself
I have to say, my moulds are not hinged - I use the paper and lift it out. But I do have a cutting guide in mine, so I take it out of the paper, put it back in the mould and cut it in to bars. The paper is just to keep the batter in the mould and let it get harder without sticking to my mould
