Citric Acid

[penelopejane]

I like Citric Acid in soap as it cuts down on soap scum which is important for high OO soap. But I've been getting spots in my soap when I use it. I thought it was the GM and I stopped using it with GM but now it is happening with all my soap. I've narrowed it down to the CA.

I dissolve it first until it is totally clear in solution but as soon as it is mixed with the oils the dots form.

Does anyone else have this problem?
Any solutions (other than not using CA)?

Also if I use dual lye in soap (5% KOH and 95% NaOH)
If I add 10g of CA I add 6.24g extra NaOH and I don't have to add more KOH as the CA has already been neutralised is that right?

 

[Obsidian]

I add the dissolved CA to my lye solution, maybe that would stop it from making the spots in your soap. Be prepared though, it will sizzle and produce fumes when you add it to the lye, do it slowly.

 

[Saponomancer]

I also dissolve it in my lye solution and don't experience that problem. It does make the lye super hot though.

 

[The Efficacious Gentleman]

Aye - citric acid isn't what you're after. You want sodium citrate which is formed by combining citric acid and sodium hydroxide.

I can't link to the guides for calculating the extra NaOH, but hopefully someone else can.

Incidentally, have you been adding in extra NaOH? If not, your superfat has been increased a little, as some of the lye would react with the citric acid instead of the oils

 

[BattleGnome]

I use this google doc that someone once linked in one of the past citric acid threads. I hand write out* the equation to figure out what I need and I hope it mostly works - my oldest bars are maybe old enough to test now.


Do you have a picture of the spots? Maybe it's an odd looking steric spot or a contaminant that someone can identify.

*I like to pretend that I use the math I learned in high school, especially since I hear lots of people scoff "when am I going to use this?" about school work

 

[penelopejane]

Thanks for your help everyone. I'll try mixing it with the NaOH.

Here is a picture. I soap with the NaOH at room temp and oils at room temp too. Something was terribly wrong with this mix because it had a rind, odd colour and the spots.

Ye,s I neutralise for the CA but only with the NaOH. If I use dual lye I don't neutralise with the KOH as well. Is that the right thing to do?

 

[The Efficacious Gentleman]

It will be okay, if you add the NaOH to the water with the CA before KOH comes in to things.

 

[Nao]

How many % citric acid are you using?

 

[penelopejane]

How many % citric acid are you using?

10g CA/kg oils=1%

 

[penelopejane]

I add the dissolved CA to my lye solution, maybe that would stop it from making the spots in your soap. Be prepared though, it will sizzle and produce fumes when you add it to the lye, do it slowly.

I also dissolve it in my lye solution and don't experience that problem. It does make the lye super hot though.

Hi Obsidian and Dragongirl,
I masterbatch my lye. Will the CA react with room temp lye/water solution?

 

[BattleGnome]

Here is a picture.

That looks like steric spots with partial gel to me. Have you adjusted temps recently or is the weather acting weird? 100% OO or something else?

 

[DeeAnna]

"...I neutralise for the CA but only with the NaOH. If I use dual lye I don't neutralise with the KOH as well. Is that the right thing to do? ..."

Yes, this is a correct way to neutralize the citric acid. You can add just extra NaOH to neutralize the citric acid even though you're also adding KOH as well.

Remember the alkali you're using (NaOH or KOH or both) splits apart when you add water. The alkali molecules divide into into sodium ions (Na+) or potassium ions (K+) as well as hydroxide ions (OH-).

It's the IONS, not the original NaOH or KOH molecules, that are doing all the work. And specifically only the OH- ions are the ones that neutralize citric acid. It doesn't matter to the citric acid where that OH- came from originally, so it doesn't matter whether you add the citric acid to the NaOH solution or to a KOH solution or to a mixture of both alkalis.

"...I masterbatch my lye. Will the CA react with room temp lye/water solution?..."

Yes.

More: https://classicbells.com/soap/dualLye.html

 

[The Efficacious Gentleman]

But wouldn't you end up with potassium citrate if you used koh? But if it is just the hydroxide that binds with it, why is it called sodium or potassium citrate?

I love learning new things about the chemical aspects of soaping [emoji7][emoji7][emoji7][emoji7][emoji7][emoji7]

 

[DeeAnna]

The dry salt is potassium citrate or sodium citrate, depending on what you make or purchase. A salt is the result of reacting an acid with a base (alkali). When you put either of these salts in water, the salt dissociates (breaks apart) into two particles -- sodium (or potassium) ions and separate citrate ions. The citrate ions are what do the work of chelating metals, not the intact salt.

When you add citric acid to a soap recipe, the citric acid dissociates in water to citrate ions and hydrogen (H+) ions. See the difference? Sodium citrate, the salt, makes citrate and sodium ions. Citric acid makes citrate and hydrogen ions.

It's those H+ ions from the acid that are the troublemakers; they need to be taken firmly in hand.

To do this, you need to balance the H+ ions from the acid with sufficient OH- ions from an alkali. The alkali (base) dissociates in water (just like the acid). If you're adding NaOH, this alkali dissociates into sodium (Na+) ions and hydroxide (OH-) ions. Those hydroxide ions react with the hydrogen ions to form tame, inoffensive water.

I'm not sure if this is answering your question, Craig -- please try again if I'm missing your point.

 

[penelopejane]

That looks like steric spots with partial gel to me. Have you adjusted temps recently or is the weather acting weird? 100% OO or something else?

100% OO yes I got new molds that don't fit in oven. I soap at room temp. It's really cold here. I am now putting them in a cooler - haven't worked out the process yet to make it work consistently.

 

[The Efficacious Gentleman]

It was perfect! So the +H and -OH combine to neutralize while the sodium or potassium ions (+) combine with the citrate ions (-) combine to form the sodium or potassium citrate?

 

[DeeAnna]

Errr, well, chemistry is a complicated thing. :crazy:

The potassium or sodium ions don't combine with the citrate ions. They pretty much remain as ions, because that's what ions prefer to do as long as they're dissolved in liquid. The ions in soap will be concentrated in the liquid phase within the soap structure. If the citrate ions find metal ions they can pounce on and immobilize, however, they will do so and become more like a normal molecule.

This is also pretty much what happens when you add any other kind of salt to soap -- table salt (NaCL, sodium chloride, the salt of hydrochloric acid and NaOH), sodium acetate (the salt of vinegar and NaOH), sodium lactate (the salt of lactic acid and NaOH), etc. These molecules largely dissociate into ions.

 

[BattleGnome]

100% OO yes I got new molds that don't fit in oven. I soap at room temp. It's really cold here. I am now putting them in a cooler - haven't worked out the process yet to make it work consistently.

I don't know how much steric is in olive oil but I'm guessing it's a similar issue of one fatty acid reacting first and cooling differently than you're used to.

For testing sake, have you used the old molds recently with the same batch oils or could you make a double batch with both molds to see if that's the issue? If you can't definitively find another reason that would rule things out

 

[penelopejane]

I don't know how much steric is in olive oil but I'm guessing it's a similar issue of one fatty acid reacting first and cooling differently than you're used to.

For testing sake, have you used the old molds recently with the same batch oils or could you make a double batch with both molds to see if that's the issue? If you can't definitively find another reason that would rule things out

THanks for the help but it is not stearic acid.
I did try both and without the CA the dots go. So it's the CA. I just have to try mixing it with the lye and hopefully the heat it causes will fix them.

The rind is another matter. I have been trying 35% Lye concentrate for the last few mixes. It is not gelling all the way through and it is really really soft. I think there is something wrong with the way I do dual lye.

 

[earlene]

Thanks for your help everyone. I'll try mixing it with the NaOH.

Here is a picture. I soap with the NaOH at room temp and oils at room temp too. Something was terribly wrong with this mix because it had a rind, odd colour and the spots.

Ye,s I neutralise for the CA but only with the NaOH. If I use dual lye I don't neutralise with the KOH as well. Is that the right thing to do?

The rind reminds me of what I got with some of my soaps made with red palm oil. The exact same look all the way around the edge of the soap. With cure the color evened out completely. From searching here on the forum, I found a few threads that talk about getting a similar rind, which does not really look like a classic partial gel.

You might find them interesting:
http://www.soapmakingforum.com/showthread.php?t=30539
http://www.soapmakingforum.com/showthread.php?t=59314&page=3

I posted a picture of my Red Palm oil soap in some thread, but it's so buried I can't find it, and link to the photo no longer works anyway because of Photobucket's policy change on 3rd party hosting. So I'll link it here.

One of the things mentioned about why it may have done that which made sense in my case, was that I used an FO that contributed to the effect. But as I said those soaps no longer have that discolored rind look whatsoever.

THanks for the help but it is not stearic acid.
I did try both and without the CA the dots go. So it's the CA. I just have to try mixing it with the lye and hopefully the heat it causes will fix them.

The rind is another matter. I have been trying 35% Lye concentrate for the last few mixes. It is not gelling all the way through and it is really really soft. I think there is something wrong with the way I do dual lye.

I don't think the dual lye would have contributed to the rind look, but I cannot say for sure. It has not happened to me with any of my dual lye soaps, and I have made many. But our formulas could be quite different.

And I cannot contribute to the CA portion of the discussion as I have never used it.