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What's left in milk soaps after liquid evaporates?


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Oops...I posted this in the wrong forum the first time.

I understand that with time, the water used in soapmaking will evaporate from the soap. What about milks? Obviously some of the liquid will evaporate, but the point of using milk is for its skin conditioning qualities, so if it all evaporates, there's no point. I'm assuming that some of the milk proteins and fats are left in the soap, but can someone tell what exactly what happens?

Thanks for your help..

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I'm no soaping expert, but I'd assume it'd be the same as freeze-drying milk. You'd end up with... milk powder! Or something equivalent to it, at least, which will probably be somewhat reconstituted when you lather your soap up with water.

Feel free to debunk this theory :D

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I had some miserably failed and grotty smelling batches using milks in liquid format - just got too hot in the moulds I think and maybe I wasn't monitoring it and removing the insulation quickly enough...

I mix milk powder (thank you to my supplier for suggesting it! lol) now with the oil for superfatting and add at trace... Same with honey powder rather than liquid honey...

No more over cooked milk in the soap but it's still going in there with all the benefits... ;-)

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Just realized that this is posted in two different sections, so here's a c&p of my response from the other thread.

I'll try to hit the major points here, but chemistry was never my strong suit.

Milk contains fatty acids just like oils (not the same fatty acids, but you get the idea). These fatty acids either saponify or remain as a superfat, unless you calculate the milk fats into your NaOH amount, most don't. There's lactic acid in milk. When lactic acid and NaOH combine, sodium lactate is produced. There have been dozens discussions all across the web about the effects of sodium lactate in soap. Some soapers add sodium lactate to their soaps to increase hardness and decrease water evaporation or shrinkage.

Also, milk contains sugars which add properties similar to using honey or sugar in your recipe. These are what cause the soap to darken or possibly overheat when using milk. However, the value far outweighs the trouble.

When all of the goodies in milk have done their thing, it's really no loss when the water left over evaporates or "cures" out.

OK, now someone with more chemistry knowledge than me can take over...lol


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