This may have been posted before although I couldn't find anything when I searched.

Something that I have discovered is that Gypsum(Calcium Sulfate) is soluble in glycerol/water/NaOH solution and reacts creating Calcium oxide and Sodium sulfate.

Calcium Oxide(lime) is insoluble and precipitates out.

Sodium sulfate is pH neutral and is easy to remove from the glycerol by cooling.

Gypsum is a very cheap way of neutralizing the glycerol.

Well Iam newbee making soap and just like to know how you remove this from the cold glycerol..
I have a problem with my Ph value... I can cook long time or Cold Process and adjust my KOH ( I make liquied soap) and more water and so on... but I can`t get my ph under 9 Ph... maybe this is the solution
for me Sodium Sulfate ...

Gert.

Gert,
a pH of 9 - 10 is normal for liquid soap. If you try to lower the pH you could be turning soaps back to fatty acids.

If you really want to drop the pH you should use citric acid or lemon juice.

Hello Rick.....

Thanks for info... I will try to use juice to start with... I was trying to bring ph down
with some vinegar but the hole batch turn to a cremy substance ... and it was not soap at all so
this was not working... but I will try the juice...

Yes I have read your book and that`s a nice one ... Lots of work to come so far... but wash hands in Ph 9-10 goes a couple of times but then it might start to burn your skin.. Well the soap is excellent.. nice and smooth really great ( made some from your book ) but in the end it might be too hard for skin because of the Ph value soo I will try to lover the Ph.

Thanks... Gert.

Gert, Thanks for the complements on the book.

When you used the vinegar what happened is you probably converted some of the soap back into fatty acids.

Soap naturally has a pH around 9. That should be safe for almost anyone's skin. In fact it is a better pH for our skin because the oils in our skin are slightly acidic. If you try to drop the soap much lower than pH 9 you end up with fatty acids in your soap.

You might do okay with citric acid (lemon juice). Citric acid is the common acid used to adjust pH in the soap industry.

But honestly... A pH of 9 - 10 is normal for soap. Detergents like SLS (sodium lauryl sulfate) that is in most liquid soaps my have a pH lower than 9...

Sinbad,

When you say neutralize the glycerin, are you referring to if there is extra caustic in the glycerin?

How are you removing the sodium sulfate?

I hardly see glycerin with excess caustic. I've recently seen my first batch when working with Tim's glycerin to help him work out a nice bar soap.

I'm in the process of modifying my SAP calculation to account for glycerin that has excess caustic. Actually having a -SAP value. In Tim's case it was about -5% SAP.

gert,
If you use the borax solution you can lower the pH while increasing the viscosity of the soap. Borax is great it neutralizes and thickens!

Gert;
The methods outlined by Rick here are spot on, however YOU DO NOT NEED TO LOWER THE PH of soap that comes in between 9-10.5, that is where it SHOULD be. It will not burn the skin unless you have not cured it (cold process) long enough for all the caustic to neutralise.

My soaps are consistently around the 10Ph area. FYI the PH cale for our purpose goes from 1 to 14 with 7 neutral. Below 7 and it begins to acidify, and above 7 it begins to become alkaline.It is preferable to have soap slightly alkaline than acid, and at 9-10.5v that is precisely what you have.

Enjoy it, you have good soap.

Couldn't have put it better.

The pH of natural soap liquid and bar falls between 9 and 10.5.

A quick an easy test is the "battery" or "Zap" test. Touch the soap to your tongue. If it bites like a 9volt battery then the pH of the soap is too high and the soap is caustic hot.

If you do not get zapped then the pH is between 9 and 10.5 and is safe for use.

quote:

When you say neutralize the glycerin, are you referring to if there is extra caustic in the glycerin?

How are you removing the sodium sulfate?

I am not sure I put this in the right thread but I couldn't work out which one was right.

I don't make soap but was trying to remove the caustic and other impurities from the glycerin which usually means an acid, the gypsum is a safe neutralizing agent for NaOH.


Sodium sulfate is very soluble when warm but practically insoluble at low temperatures. I put some in the freezer and it just fell out of solution if left to cool slowly it makes some nice crystals.

This is the right area.
The soap discussion sort of hijacked your thread...

So what you are saying is you have glycerin that is high in NaOH after you have made biodiesel.

You want to neutralize the NaOH. And you are using gypsum to do so. And both the Calcium oxide and Sodium sulfate fall out after the glycerin cools.

Sinbad,
That is a great Idea. No hazard materials to handle!
I beleive what your creating though is, Sodium sulfate and Calcium Hydroxide.
2NaOH + CaSO4 -> Na2SO4 + Ca(OH)2
Keep us posted on the process.

... hey Rick ang Legal... well might be I just have to wait for the curing period.. but I have HP all my soap and it ended up Ph 9-10 and it`S a great soap.. The only thing I was wondering about was that normal soap you buy have a Ph of 7 and mine 9-10 so that`s why I was worried about my skin.

But I will let my soap cure for some weeks and see what`s happening with Ph.
I have washed hands every day and have not burned my hands but they were dry at the last.. but that would happen to ordinary soap too I think so... but I will works a little with borax I think and lemon juice..

Thanks... Gert

the difference between your soap and "ordinary" soap is that ordinary soap, in most cases is a detergent. Detergents will have a pH around 7. Natural soap, Like ours, has a pH of 9 - 10.5.

You pH falls right were it needs to be without neutralizing.

In fact if you are going to use borax to thicken your liquid you should make the pH 10.9 - 11 on purpose and allow the borax to lower the pH to between 9 and 10.5.

Basically you are already there, and it sounds like you have some great soap!

Congradulations!!!

Sinbad, Does the FFA split out from the Glyc in the same way it does if you add acid? or is this just a method to shift the PH back towards 7

Hi Cineman short answer is no.

Gypsum is pH neutral so it doesn't split soap but it does convert the residual lye into sodium/potassium sulfate which reduces the amount of acid you need to use to split the soap. You would need to let the lime created drop out and separate before the acid is added or the acid will react with the lime.