What % Citric Acid do I need to chelate (liquid) coconut soap?

[Liquidsoaper]

My house has hard water, and my DIY 100% coconut oil-based liquid soap (I used distilled water to dilute) is leaving soap scum when I rinse it off. For my next batch, what percent of citric acid should I add to help chelate?

Is there any difference (besides adding more KOH) between using citric acid vs. potassium citrate?

Thanks!

 

[DeeAnna]

If you are using coconut oil soap for dishwashing, be aware that a chelator cannot eliminate soap scum if you're using the soap in a basin full of hard water or in the washing machine. A chelator is overwhelmed in this situation. You're going to get better results if you want less soap scum by also using a water softener product such as washing soda to the wash water or using a whole-house water softener.

A chelator will perform best if the soap used for "spot" washing where you put the soap on a scrubby and use it directly on the dishes. In other words, any situation where you give the chelator only a small amount of hard water to deal with.

The citrate ion is the chelator. Makes no difference whether it starts as potassium citrate or sodium citrate.

See the acids and chelators section in my articles -- Table of contents | Soapy Stuff -- and look in particular for the article on citric acid and "limitations of chelators".

 

[Liquidsoaper]

A chelator will perform best if the soap used for "spot" washing where you put the soap on a scrubby and use it directly on the dishes. In other words, any situation where you give the chelator only a small amount of hard water to deal with.

Thank you! That link was incredibly helpful.

I have to test my water. But, let's say I assume the worst, and my water is very hard (+180 mg/L). What's the maximum % of citric acid I can add to my soap before it starts creating undesirable effects? And what would those effects be?

 

[DeeAnna]

I answered that question in my article about citrate --

"...Many soap makers use 10 g to 20 g citric acid powder for every 1,000 g fats (1% to 2% ppo).

While this advice is slanted toward using it in bar soap, the same advice holds true for liquid soap. If you load up a liquid soap with any kind of salt (including citrate) with something over about 2% by weight, the soap will become water thin. That's one downside I know about. I've not tried using lots of citrate in liquid soap to know what other side effects there would be, nor do I know of anyone else who has talked about doing this. You'll have to see for yourself.

 

[maya29]

I think that I will use acid citric soon.
Marie Mousse, an canadian woman, explain on You Tube how we can use citic acid in ours soaps. But it's in French... 10g or 20g is used.
After, we've got to recalculate the lye.

 

[Zany_in_CO]

I've not tried using lots of citrate in liquid soap to know what other side effects there would be,

NB: Citric acid should be used with a light touch. Too much and your soap will separate.

After, we've got to recalculate the lye.

Correct.

Reseach Notes On Citric Acid Use from my Files:

Citric Acid can be used as a chelating agent (like sorbitol, sodium lactate, sodium gluconate) and is used to reduce soap scum, especially useful if you have hard water. It reacts with the lye to form sodium citrate.

When using CA in CP/HP soap...you have to add a bit of extra lye to compensate for the oils that the CA brings out of the batter...CA counteracts lye, so to make up for that, I add 0.571 oz of lye for every oz of citric acid.

EXAMPLE: So if you are using 0.25 oz of citric PPO (Per Pound Oils)...and making a 32 oz batch of soap:

2 (lbs) oils x 0.25 = 0.5 oz CA
0.5 oz. CA x 0.571 = 0.2885 oz extra lye (i would use 0.3 oz)

Use rate is 0.1% to 0.5%. Up to 1 tsp. (1-5 grams) ppo
SAP value is 0.571 for monohydrate citric acid.
SAP value is 0.625 for anhydrous citric acid.

Add citric acid to oils before adding lye water. If you add it to your water, add the lye slowly and carefully. The citric acid will cause some excess bubbling and splashing.

FOR LIQUID SOAP: Make up a 20% Citric Acid Solution. Add to diluted LS at a rate of 0.06% to neutralize excess lye. More often than not, it flakes out when added. In that case, warm the batch to 140°F and mix gently until fully incorporated. Note: When tested after a full 2-week sequester, it seems to lower the pH a bit.