CP Sodium citrate addition

I was going to just PM Sonya/Newbie about this b/c their posts have been really helpful. But still don't get it, fully, and thought doing a public post might be helpful if other people were stymied on the subject and searched later.

I would like to add a 3 % Sodium Citrate solution to soap as a chelator/anti-scum measure. Did a pretty exhaustive internet search, lots of references to SC, but not so much about how exactly to add it. Currently I add EDTA as a chelator, but if I had not read Irish Lasses' posts on it, I would not have know that you cannot add it at more than 39% (powder to water), or it will not dissolve fully. Am concerned that SC has some of the same issues, but cannot find any exact guidance.

After doing a pretty exhaustive internet search, it seems like people hold out some of the water, dissolve the SC in it, and then add it to the lye water mix.

So the questions: is that the right way to do it? Any recommendations for maximum amounts of SC to use in terms of optimal solubility? If I want to masterbatch it (eg) make up a lb to add to several batches, is there a way to figure out how to (a) get the solubility percentage right and then (b) figure out a ratio at which to add the correct amount of masterbatch solution?

Also, when to add the master batch solution - to water, lye/water mix/at trace?

Sorry, I know this is super confusing. I am just hoping it makes sense to someone who has already done it.

I've never masterbatched my SC water solution. I tend to do a 50% lye solution then take the remaining water and add my SC to that. I add this water to my oils before my lye water

I do it exactly the same way as SOnya. I don't add any sodium citrate to the lye water. I did that once and it heated up a lot which concerned me because I didn't know what reaction was causing that so now I add about 3% of my oils weight in SC to plain water, which I then mix into my oils. It dissolves quite readily in the left-over water but I have never played with the solubility to know exactly what proportion of water I have to use to get it to dissolve. I could probably use less water but I don't know how low i can go.

I've read more than 3% can start decreasing the hardness of your finished soap. Again, I have not tested this myself but I see no reason to go higher than the 3% because it seems to work and why use more than necessary? I can research a bit and find the least amount of water needed, and you can use that to masterbatch, but it doesn't take long for SC to dissolve so dissolving it with each soap batch is not a major time suck.

How to determine what you needed per batch for per pound or per ounce of oils would depend on the solubility. It it's 3:1 water:SC your calculation will be different that if it's a 1:1. Let me research so I can stop talking in theory.

DIsodium citrate says its solubility is 29.2g/1 liter of water. I must have trisodium citrate, which is use in food prep and in the lab because that has a solubility of 92g/100g water which correlates much better with what i have experienced. SO you could make a solution that is close to a 1:1. If you make a 30 ounce oil batch, you'd add 0.9 ounces of sodium citrate max. If you want to be ultra-scientific about it, you can calculate exactly how much SC would be in each ounce of water and go from there. For me, a close approximation would be adequate, so if I made a 0.9:1 solution (SC:water), I would add 2 weighed ounces of the solution to my oils. That would be slightly higher than 3% but not be enough to get me wound up.

Does that make sense or even answer your question?

Yes, it does, Newbie, thank you. I have to say I love you kind posters who take the time to help out, I have researched quite a bit on this topic, and this makes it so much more clear.

Edited to add: wanted to thank you again for taking the trouble to do research on this. I am kind of a numbers idiot, so it really helps when you people who are good at it get me to the point that it is understandable. I am just going to plunge forward with the frigging stuff soon and see what happens. I hate the water that comes out of my taps.

I add CA to water, after than dissolved sugar then lye. I had noticed no additional heating or have any issues with it.

As above, I add ca and sugar to my water before adding lye. I wonder if the difference is that the lye can react with the ca but not with the sc? I don't know why that might cause heating, unless the lye gets annoyed and heats up in a tantrum

I used to add the SC to my water before the lye but I added sugar and salt once too and something didn't work. They all appeared to be dissolved but when I'd added my lye and let it cool I had crystals in the bottom - these could have been salt, sugar, SC or lye. So I don't risk it now - I just dissolve any additives in the extra water & add this to my oils and use the 50% lye solution.

Someone posted a formula for increasing the amount of lye in correlation with how much citric acid one was adding, is there not something similar for sodium citrate?

sodium citrate is the result of NaOH reacting with Citric acid. Since it is already a salt of an acid and base, there is little to no reaction. You will have some Na ions swap out with the ones on the citrate molecule, but that still leaves the same thing. Since the OH and the citrate are both negatively charged, they won't usually react at least not without some other help.

So, there is no need to add extra lye if you are using Na citrate.

I take some water off to warm it and dissolve the sugar, CA dissolve very well in my room temp water. When it is mixed I add sugar solution back then lye, no cristals left, just make sure you use the mixing motion to dissolve everything.

I add a TB of sugar ppo as well to help w/lather, did not even consider how this would mix in w/the SC. I guess I am just going to have to mix up some (small) batches and see how it works. I know that is part of the fun of it, but right now I am expecting some failures. Which is OK.

Ann, several people were great about posting formulas about adjusting lye for Citric Acid, and Irish Lasses' posts have been a godsend about adding/masterbatching EDTA. But I couldn't find anything that was really specific about amounts/masterbatch additions for Sodium Citrate (definitely different b/c you don't need additional lye) . I think maybe less people use Sodium Citrate, and less people ask about it, so not so many posts. But now I have 2.5 lbs of it, (love Ebay) and would like to figure the best way to get it in there.

Thank you all for responding here.

CITRIC ACID in Soap

Typical dosage: 10 g citric acid for every 1,000 g oils (1% ppo). Range 0.1% to 3%.

Citric acid and Sodium hydroxide (NaOH) make Sodium citrate in soap
10 g citric acid neutralizes 6.24 g NaOH

Citric acid and Potassium hydroxide (KOH) make Potassium citrate in soap
10 g citric acid neutralizes 8.42 g KOH

Stir the citric acid into the water you will use to make your lye solution. Add the lye to the water and proceed with your recipe as usual.

***

SODIUM CITRATE or POTASSIUM CITRATE in soap

If dosage rate you want for citric acid is 1%, the equivalent dosage for sodium citrate is 1.3%

If dosage rate you want for citric acid is 1%, the equivalent dosage for potassium citrate is 1.6%

Do NOT add additional lye if you are using potassium or sodium citrate. Extra lye is only needed if you are using citric acid.

Stir the citrate into the water you will use to make your lye solution. Add the lye to the water and proceed with your recipe as usual.

******

"...I used to add the SC to my water before the lye but I added sugar and salt once too and something didn't work. They all appeared to be dissolved but when I'd added my lye and let it cool I had crystals in the bottom - these could have been salt, sugar, SC or lye...."

It was most likely the salt falling out of solution as fine crystals when the lye changed the solubility of salt in the mixture. People see this with the lye solution for solseife soaps; that's why the advice is given to add the salt first and the lye second -- any salt that falls out of solution when the lye is added are tiny crystals that aren't objectionable in the finished soap. If you do the reverse, some of the salt crystals won't ever dissolve and they will remain as larger particles in the finished lye solution, so you'd want to strain them out for appearance's sake.

******

"...I don't add any sodium citrate to the lye water. I did that once and it heated up a lot which concerned me..."

The heating created by dissolving trisodium citrate (the usual stuff you'd use) in water is very small -- in a typical recipe (see below) the temp rise would be about 1.2 deg F (0.7 C). I don't think there should be any other chemical reaction going on with the citrate that should add more heat, so I'm a bit puzzled by your finding. Not to say it wasn't real, just I'm not understanding what's going on fully.

There ~is~ some heating caused by including citric acid (CA) in a soap recipe. I did some digging today and if the numbers I found are correct, here's what you'd get for adding citric acid:

If I dissolved 10 g CA in 400 g of water (a round-number amount of water for a "full water" recipe with about 1000 g of oils), and added just the lye needed to react with the citric acid, I calculate that should release about 3000 calories of heat. The temperature rise in the water caused by this heat release would be about 13.5 deg F (7.5 C). (I'm focusing just on the heat released by the CA and NaOH reaction and ignoring the much larger amount of heat released by dissolving the lye in the water without any CA involved.)

I don't know if that temperature rise is "a lot" compared with the temp rise caused by dissolving lye in water, but it's certainly there.

Whether you add the CA to the water or add it to the oils or whatever, the same amount of calories will be created by the reaction of the NaOH and the CA. If you add CA to the fats, you are basically causing the reaction to happen later in your soap batter rather than up front in the lye solution. The temperature rise in this case will be somewhat lower because there's more mass in the soap batter vs in the lye solution, but a temp rise will still happen. This ~might~ increase the rate of trace, so it's something to keep in mind if you are working to get a slow-trace soap.

:::sigh::: I love DeeAnna's posts - they need to be compiled into a book!

Yes, they really do. Thanks, DeeAnna! And everyone else who has been kind enough to take the time to chip in with thoughts.

I am having sodium citrate difficulties, I used it at 3% of my oils and twice it has given me soap on a stick. It was the only new thing in my recipe and I soaped really cold so it has to be the culprit. Any ideas about where I'm going wrong?

I thought using sodium citrate would avoid faster trace as it wouldn't react with the lye.

I don't know what to say, Saponista. I was looking for info about CS and trace some time ago and found an old post in which someone said it accelerated, but I have not found it to be a problem in my recipe. Have you tried bringing it down to 2% to see if it's still a problem? Still, I'm not certain why it would be so problematic. HOw did you dissolve it and add it to your recipe?

I'm also using 3% trisodium citrate powder in the water along with sugar and salt[or]sodium lactate before adding 50% Lye Solution, and since then I have bigger bubbles in all my soaps.

I've only recently started to us sodium citrate at 2% (about 5 batches) and I noticed a modest increase in acceleration: my recipe was is about 65 - 80% hard oils, soaping with 33% water and room temperature.

I maybe crazy here, but I swear the sc added to the lather even though we have soft water. (most people I give soap to have hard water). One very small downside was that the sc gave a slightly yellow tinge to my very white tallow/lard bars, and changed the natural scent as well. Anyone else notice this?

Check out the lather lovers swap - they noted that SC increased lather too http://www.modernsoapmaking.com/lather-lovers-additive-testing/

I added it to the water before adding the lye newbie. I was using 30% lye concentration and had 50% hard oils. I will drop the percentage to 2 and maybe try 1 as well and see if that helps. It traces in seconds after about three stick blender bursts and then I have to move like a mad thing to get it into the mould, no chance for colour or anything. It does make lovely hard soap though with a definite lather increase.

I tried again today but added the 3% dissolved in water to my oils and stick blended it before adding the lye. It still traced fast, only needed a couple of stick blender bursts, but I would have been able to colour it if I had wanted. It was oat, gm, lavender so I left it plain. I will try a coloured version tomorrow. I definitely wouldn't use it in swirl challenge soaps as it just speeds trace way too much. Did you use it in your spin swirl soap Sonya?