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Why Freeze Milk/ Juice When Mixing With Sodium Hydroxide (lye)


A reader asked me yesterday like why do we have to freeze milk and juices when mixing with sodium hydroxide in cold process soap making.

Now before we go into detail on the why; let me tell you something about sodium hydroxide (lye) first.

Sodium hydroxide is caustic soda and its used in soapmaking to create ‘saponification’ where it helps in converting the fatty acids in oils (coconut oil, olive oil etc) into soaps.

The end results (soap) usually wont have any sodium hydroxide if you followed the correct measurement according to this soap calculator.

So anyways; sodium hydroxide usually heats up when in contact with liquid.

A normal room temperature water when mixed with sodium hydroxide flakes will give a solution thats almost 100 degrees celcius. Thats very hot!
Since water dont ‘burn’ it wont smell bad.

But if you are using milk/ juices that burns easily; you will need to freeze it first before mixing with sodium hydroxide. 

By mixing frozen milk/juice with sodium hydroxide; it will control the heat to about 40 degrees therefore seldom burning happens. If needed; you can also add ice bath around the container you are mixing the caustic soda & milk/juice with to further control the temperature.

So conclusion is; the next time you are making cold process soap and not using water as the diluent; make sure to freeze it first. And always use thermometer!! 

Thank you for reading

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