Goat milk soap recipe – and why it is hard to keep it white
The question can be asked also from the other point of view: why not to enhance soap by adding some goat milk?
A lot of people love goat milk soap, claiming that it is the best for problematic and sensitive skin. I have no personal experience (since my skin has no problems), so I cannot confirm, but it seems it is very pleasant to use!
Goat milk can be made using any basic soap recipe just substituting water for milk.
However, there are some tricky parts (as with any milk soap) that you should familiarize yourself with…
For instance when you dissolve NaOH in milk:
- the proteins in milk are hydrolysed and coagulate, which releases unpleasant ammonia smell – it also makes milk thicken
- milk fats are turned into soap and milk thus thickens even more
- due to the heat released by NaOH when dissolving, milk sugars turn brown and discolour milk to yellow
This is why we try to keep the temperature of the lye solution as low as possible and therefore we freeze the milk before dissolving lye in it.
Another point is that thanks to sugar content milk soap heats very quickly, which means that:
- you shall not add anything accelerating the trace (or only very carefully), like more sugars, some alcohol based fragrances, some essential oils (for the record, one of them is cinnamon, which I use below… 🙂 ),
- keep the process cold and in the summer I would not use the log mould… you can get volcano effect (the soap heats too much and runs out of the mould…)
- better avoid the hot process or cold process in oven process method…
When it comes to keeping milk white, it is even more difficult. There are many variables that influence soap colour, in between them:
- oils used (each oil gives a different colour)
- if it passed the gel phase or not (gel phase darkens the soap)
- all the additives, including essential oils and fragrances!
So I decided to make an experiment and make goat milk soap from a mix of oils that together don’t give by default very white soap and tried to find out, how gel phase as well as added essential oil influence the colour. Since I knew that with cocoa butter and cinnamon oil I won’t be expecting very white soap, I also opted for adding a well known whitener: zinc oxide (ZnO) to the part of the soap. Another option is to add Ti2O (titanium dioxide).
The recipe I tried is a bit unusual (and I do not recommend it for beginners) – I used stearic acid to make the bar harder (simply because I had not much butters).
The goat milk soap recipe
778g goat milk (350g frozen into cubes, 428g cold from fridge)
250g stearic acid
350g cocoa butter
400g rice oil
1000g olive oil
40g ZnO (zinc oxide) + 50g glycerine -> mix in advance and add to 1/2 soap mass
twice this EO blend
10g EO lavender
14g EO lemon
8g EO cinnamon
1. I melted stearic acid and cocoa butter in rice bran oil and olive oil. Note that at the temperature below 50°C stearic acid will start to solidify again. That means the soap must be mixed at 50°C – this is a relatively high temperature for the milk soap, but I tried it.
2. I slowly dissolved NaOH in the milk – to keep the color as white as possible, try to keep the temperature as low as possible – this might mean to add the milk ice cubes during the process. I did not freeze all the milk, since it is very difficult and slow to dissolve lye in the milk ice cubes only. It is also good to keep the pitcher with lye in ice water.
Be sure that you dissolved all the NaOH before pouring it into the oils!
3. Then I poured lye in the oils and stirred well by hand. It thickened very quickly due to the oils (stearic acid and cocoa butter) cooling down. Also, stearic acid reacts very quickly with lye. It is important not to cease stirring – after while, the soap will thin again.
4. I added ZnO into half of the soap and blended it in with a mixer, which caused the soap to trace very fast until separation occurred – I expected this, since this soap traced already very fast hand stirring, however, blending is the only way to distribute ZnO in soap evenly. Normally, that is the reason why I would have dissolved ZnO in the milk first.
5. I spooned into smaller moulds some unscented soap (both ZnO and without ZnO) –
this way I could be sure the soaps won’t gel (also because it is colder, in the summer, they might have gelled in individual moulds, too).
6. Then, I hand stirred the EO blend to the rest of the soap (both with ZnO and without ZnO) and spooned it into my big log mould (see image below).
7. 12 hours later, I unmoulded the soaps – the non-gelled unscented ZnO soaps were too soft, so I had to freeze them prior to unmolding.
The image below shows the difference in goat milk soap colour based on its ZnO and EO content and if it passed gel phase or not. I also added pH test!
To sum up, if you wish to succeed your goat milk (or any milk) soap, and make it as white as possible:
- freeze the milk and keep the temperature as low as possible when mixing in NaOH – do not let it get yellow
- use oils that give the whitest soap, such as olive oil, grapeseed oil, fractionated coconut oil, sunflower oil, rapeseed oil, rice oil, … and that do not have to be heated too much in order to melt (e.g. coconut oil is fine, however shea butter or cocoa butter are not)
- … or if your oils do not give very white soap, or you wish it really very very white, you can add zinc oxide – ZnO or titanium oxide – Ti2O (app. 30g-60g per 1kg of oils) – however, beware that if your soap is too thick at trace, your soap will after blending in the ZnO separate. You better dissolve it in milk prior to adding lye.
- beware of essential oils that discolour soap (e.g. cinnamon, clove bud, but also citrusy essential oils, which turn soap yellow!)
- do not let the soap pass the gel phase, which darkens the soap tan – either use individual moulds, or put the mould into the fridge
… and do not forget you can turn almost any soap recipe into milk soap, however, bear in mind what I wrote above!
PS: There are other methods how to add milk or other diary products to soap, the two most common techniques (cold and warm – this one is cold) are described well in detail the book of Anne L. Watson: Milk Soapmaking:
Check my other posts where I use milk or other diary products in soap: