# Math check for citric acid

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#### gdawgs

##### Well-Known Member
The hard water thread got me wanting to try a recipe that I've already made but add the citric acid for comparison. Attached is the recipe from Soap Calc.

If I'm understanding everything I read correctly, a good usage rate for citric acid is 1% of oils. So my batch is 794 g(rounding up to the nearest gram), so I should use 7.94grams of citric acid, I'll round that up to 8g.

That 8g will use up some of my lye at a rate of .624 g of lye per gram of citric acid. So 8 x .624 gives me 4.992 g, which I'll round up to 5 g. Therefore I need to add an extra 5 grams to my total, so I need a total of 115 grams of lye.

Did I get all that right?

Then when I'm making up my lye water, I just take the 234 grams of water, stir in the 8 grams of citric acid, then add the 115 grams of Lye?

I just want to make sure I'm understanding everything correctly before I try it out.

View attachment Soap.pdf

#### Steve85569

Supporting Member
Math checks.
Citric makes heat in the reaction so be prepared for HOT water when you add the lye. DO NOT have your face over the container AT ALL. DO NOT breathe the fumes.
That does it for my rant. It is a real interesting experience the first couple of times.
I start with really cold water out of the fridge when doing this. My distilled soaping water lives there.

#### TeresaT

##### I see you.
Hmmm, Steve, that's interesting. Gdawgs, I've never noticed any heat from the citric acid. But I don't usually pay attention to that because I weigh my (room temp) distilled water and my citric acid then mix and stir well. I put that off to the side and start weighing my oils (check on the CA/H2O mix every now and then to make sure it's dissolving well giving it a few stirs). When my oils are all weighed, I'm ready to melt the hard oils. I dump my NaOH into the CA/H2O and stir until it's clear while the oils are gently heating up on the stove. Melted hard oils join liquid oils, lye solution with CA joins the oils and I'm stirring by hand until I get bored with that. (It doesn't take long for me to get bored with anything.) I stick blend until emulsion (or pudding, which ever I notice first), then mold that sucker and put it to bed. Then I get really bored with the clean-up and procrastinate like the pro that I am. (BTW: wait until you swap out vinegar for water. Now THAT's some pretty hot stuff. Seriously. It almost boils. You don't want any body parts near that. I usually use a small pitcher when I mix my lye solution. Not when I do the vinegar. I use a big bowl. I want as much surface area as possible to dissipate that heat as quickly as possible over a larger surface area and definitely not straight up. It's fun to watch, though. And you probably "should" do it in a narrow-ish container at least once just to see the volatility of the reaction. If you're into that sort of thing. Usually, I can touch the side of the lye solution pitcher after 5 minutes with distilled water. Vinegar takes a good 20 minutes or more to be comfortable to the touch.)

#### gdawgs

##### Well-Known Member
Thanks for the heads up and math check.

I must be missing something here. What do you use vinegar for?

#### TheDragonGirl

##### Professional Geek
Thanks for the heads up and math check.

I must be missing something here. What do you use vinegar for?
it hardens the bar and makes unmolding faster and cleaner, there are a couple of threads on it, and all the experiments surrounding it and the calculations used.