I think I've done it!
The great thing with homemade soap is that you can use any oils you like, and adjust the lye accordingly using an online soap calculator such as this one. I have found that a 1.5kg batch of oil easily fits in my mixing bowl, so I have been making my soap using this quantity. I enter the quantities of each oil I'm using into the soap calculator, specify the liquid and press "calculate lye" and it will tell me exactly how much lye (caustic soda) to use. On the right hand side is a table where you can select how much excess fat you want in the soap, I have been going for somewhere around 6-8%, (this ensures that all of the lye has a chance to be converted to soap, and not be present in the final product, which would otherwise cause skin irritations).
GOATS MILK, HONEY AND OATMEAL SOAP
For this batch of soap, I used the following:
1kg olive oil (66.6%)
500g coconut oil (copha) (33.3%)
500ml liquid (150ml water and 350ml goats milk)
209g Lye (caustic soda)
3 tablespoons honey
ground oats, about 1 cup
**Remember to wear safety goggles, rubber gloves and a face mask when using caustic soda. Have the room well ventilated**
...and this is how I made it:
First add the lye to the water in a heatproof container (a pot is ideal), stirring to dissolve. Allow to cool in a safe place where it can't be knocked over. If you are going to leave it for some time, place a lid on it so it doesn't lose it's strength.
Melt the coconut oil in a large pot. Allow to cool. Add the olive oil and honey.
Add this to the oils and stir well. The lye will react to the sugars in the milk, turning it a tan colour. Either transfer to a mixing bowl and use an electric stand mixer or use a hand-held mixer to mix the ingredients together well. Mix constantly for the first 15 minutes. After this, it can be left for about 15-20 minutes at a time and returned to for 5-10 minute mixes.
This soap mixture took about 1 1/2 hours to reach a trace (thick custard-like consistancy). Once this is reached, add the ground oats and mix well.
Pour into a mould (I used a plastic container from the cheap shop, lined with plastic wrap), and seal with a lid to prevent soda ash forming on top of bars. Place in a safe spot at room temperature and allow to sit for 1-2 days, undisturbed. Do not insulate the soap during this time, (milk soaps really don't like heat, trust me, this I know ;-))
Allow the bars to air dry for 4-6 weeks in a warm, dry room. An open cardboard box or cake rack are ideal to store the soap while they are curing. The longer the soap sits, the harder and more milder it will become.
My finished goats milk, honey and oatmeal soap. The litte flecks you can see are pieces of oatmeal scattered throughout the soap. Now the hard part comes - waiting for it to cure.