Stacey
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Concentrated caustic soda for soap?I've just got some caustic soda from B&Q but it says it's concentrated  Is it still ok to use for soap or will the amounts be different?
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Sade
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You have to know the % of actual caustic soda that it has.
Say, your product is 75% caustic soda, and the rest is *whatever* (hopefully, not dangerous chemicals - if they are, toss it and find pure caustic soda).
Then you do some math: You need for certain recipe 120 grams of pure caustic soda, then of your 75% caustic soda you'll need 120/.75 = 160 grams.
Use the new weight and proceed as usual
(Disclaimer, I havent made soap yet, I'm just talking in math terms. Do not use caustic soda that has other unknown chemicals!)
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sally_in_wales
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The B&Q stuff is normally the right stuff, it should be white granules and the lable should say nothing except caustic soda or sodium hydroxide. Its very unhelpful of them not to be more specific, if they did have a percentage then yes, maths would need to be applied, but unless they have changed their range in teh last month or so, its the right concentration
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Stacey
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I've even tried to find the data sheet on their site but despite them saying it's available I can't find it. It doesn't say on the bottle what percentage it is either 
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sally_in_wales
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is it the stuff in the white plastic bottle? If it is, I've used it and its fine
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Stacey
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Yeah, and it's the only one they sell. I have a vague feeling I had this dilemma before
I'll crack on with it now you think it's ok, sally 
I have some coffee grounds I want t try putting into some soap.
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cab
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If its the white granules from B&Q, then its a quite startlingly pure grade of sodium hydroxide. Nasty, dangerous studd, but just precisely what you want for soap.
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BahamaMama
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Having just made soap for the first time, I don't understand how something that is so nasty in a pure form can be suitable for washing all those delicate nooks and crannies. Can someone offer a (laymans) explanation?
I am concerned as himself does suffer from excema and I don't want to damage him.
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sally_in_wales
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| BahamaMama wrote: | Having just made soap for the first time, I don't understand how something that is so nasty in a pure form can be suitable for washing all those delicate nooks and crannies. Can someone offer a (laymans) explanation?
I am concerned as himself does suffer from excema and I don't want to damage him. |
Its because soap is made with a strong alkali, but the end product doesnt contain any.
The short version of it goes like this. When you mix clean fat with a specific amount of alkali, a chemical reaction takes place. In a 'perfect' reaction, the end result contains approximately three parts of soap and one part of glycerine, there is no leftover fat or alkali.
In reality, we try to leave a little leftover fat as this makes the soap more pleasant to use. if you however leave a little excess alkali you get something that cleans well, but is unpleasant on the skin, hence the mixed reputation of 'lye soap' over the years.
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BahamaMama
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OK - I am convinced, he can have a wash, in a couple of months....
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sally_in_wales
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Double checking is fairly easy, when the soap is ready, touch it to your tongue, the end of your tongue is really good at identifying if any alkali is present, if you don't get a 'tingle' and it just tastes soapy, its as mild as you would wish soap to be
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cab
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The only thing to add to what Sally has said is that fats are a weak acid. Sodium hydroxide, or lye, is the opposite, its a strong alkali. You've got a measure of how much alkali is needed to mostly neutralise the fat, its called the saponification value.
Now this is the clever part. The fats, being a weak acid, well that gives you a margin of error; it means that its harder than you'd think to mess it up to the point where you've made something dangerous. If you put in not quite enough sodium hydroxide you've still got something safe, you only get something nasty if you put too much in. So most soap recipes you see have got a little margin of error built in.
Of course soapers will tell you that this is 'superfatting' and its all to make a better bar of soap. Thats also true, of course, but its not the only reason.
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Stacey
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| cab wrote: | | If its the white granules from B&Q, then its a quite startlingly pure grade of sodium hydroxide. Nasty, dangerous studd, but just precisely what you want for soap. |
A nasty, dangerous studd sounds right up my street right now  
I made 3 small batches today - 1 coffee & coffee grounds, 1 rooibos tea and one comfrey and pumice. The coffee one is very putty-like and has excess water Any chemical reason why this should be?
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Blacksmith
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Is it the same as caustic soda liquor ?
We have a 2000 L tank at work we use in the manufacture of paste.
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