Fixing a mistake - clarification request

[LBV]

Hi there, I was making a laundry soap using Jan Berry's pure coconut recipe, with a small change. Unfortunately, I used the wrong lye. As it has the purpose of laundry use, I can't use it as is, so my plan is the following. I am wanting to know if my thought process and calculations are right (I am relatively new to soap making).

The recipe called for 794gm coconut fat, 248gm water, 146gm lye (NaOH).
I used 146gm KOH. As KOH requires a larger amount of lye, the mixture is currently superfatted, more lye is needed to get a 0 superfat.

If the amount of fat is multiplied by the saponification value equals the amount of lye required. Therefore I divided the amount of lye I used by the saponification value to get the amount of fat that was saponified.

146÷0.2690=543.

Subtracting the amount of fat saponified, should leave me with 251gm of fat available.

794-543=251

My plan is to melt the soap and add NaOH to make a solid bar.

251×.1910=47.9 (round down for safety).

Is my plan and calculations viable. Appreciate any advice.

 

[SaltedFig]

Hi there, I was making a laundry soap using Jan Berry's pure coconut recipe, with a small change. Unfortunately, I used the wrong lye. As it has the purpose of laundry use, I can't use it as is, so my plan is the following. I am wanting to know if my thought process and calculations are right (I am relatively new to soap making).

The recipe called for 794gm coconut fat, 248gm water, 146gm lye (NaOH).
I used 146gm KOH. As KOH requires a larger amount of lye, the mixture is currently superfatted, more lye is needed to get a 0 superfat.

If the amount of fat is multiplied by the saponification value equals the amount of lye required. Therefore I divided the amount of lye I used by the saponification value to get the amount of fat that was saponified.

146÷0.2690=543.

Subtracting the amount of fat saponified, should leave me with 251gm of fat available.

794-543=251

My plan is to melt the soap and add NaOH to make a solid bar.

251×.1910=47.9 (round down for safety).

Is my plan and calculations viable. Appreciate any advice.

Coconut has a NaSAP of 0.1910 and a KSAP of 0.2690

794g of coconut x 0.1910 = 151.6g of NaOH (note that this is higher than 146g - you had a superfat built into your original recipe)
794g of coconut x 0.2690 = 213.5g of KOH

You are correct in thinking that 146g of KOH for this amount of coconut is going to leave you with a heavily superfatted soap.

The amount (expressed as a percentage) of hydroxide you are short of can be calculated by taking the actual amount of KOH you used and dividing that by the required KOH amount. Take that number from 1 and express it as a percentage gives 31.6% more hydroxide is required.
(Calculation: 1- 146/213.5 = 31.6%)

If you want to add enough hydroxide to get to a zero superfat, then it is as simple as multiplying the require NaOH by the percentage needed, which results in 47.9grams of NaOH.
(Calculation: 151.6g Original NaOH * 31.6% = 47.9grams NaOH)

If you had wanted to leave a superfat (or rather, a lye discount), then you could factor that it by reducing the percentage hydroxide required.
(Eg. a 5% lye discount could be calculated as 0.95 x 31.6% = 30%, so the additional NaOH would become 151.6g Original NaOH * 30% = 45.5grams NaOH)

Is my plan and calculations viable. Appreciate any advice.
Yes, your plan is viable.
I have calculated the figured using a slightly different method and reached the same number (add 47.9grams of NaOH to bring the soap to a zero superfat), so the required hydroxide amount is confirmed.

You will need to add extra water (use a minimum of the same weight of water as you have dry hydroxide) to dissolve the extra lye, so that will mean that you have a lower lye concentration that you original used. Because your original lye concentration was fairly high (the lye concentration was strong), the final water content will still be within a reasonable amount.

I would be interested to hear how you go mixing in the extra lye solution and also how firm your zero superfat, 69.4% KOH to 31.6% NaOH coconut soap ends up being.

Good luck!

 

[LBV]

Thank You SaltedFig. I appreciate your response.
The soap I initially made was a very solid gel. I could spoon it easily, but it needed to be stirred with a large spoon, not a regular dessertspoon. The main reason for this was that I added about 20% sea salt to the initial liquid when making the soap. For that reason, I added a little extra water to the NaOH solution and also to the soap mixture while melting it. It did make it a lot easier to stir. I added the NaOh solution to the mixture, stirred well and poured it into the mould.
I left it about an hour or so, then went to check on it. It was solid enough to remove from the mould and cut into slices - which I did. The majority of the mixture was solid white with a small partially translucent area in the middle of the slices - I am figuring that will change overnight. It cut easily.
I had decided to use salt in the bar to lower the lathering effect of the coconut oil. I was able to find some of my old stock of commercial soap so will be able to leave this to harden properly before using.