Lye & water Calculations

[Kerrie28]

Hi
I’ve recently started to have an in-depth look into lye and water (liquid) calculations. I always use an online calculator like soapcalc but really wanted to know all the ins and outs.

So here is my calculation based on 1000g Olive Oil
example.
1000 x 0.1353 SAP for Olive Oil = 135.3 lye amount

135.3 x 0.38% as used by soapcalc = 356.05

Total lye solution 356.05 - 135.3 = 220g of liquid.

obviously there is no superfat in my calc and I removed the % from soapcalc.

My question is why is the water value in soapcalc coming out at 380g?

thanks for any help with understanding this.

 

[earlene]

Hi
I’ve recently started to have an in-depth look into lye and water (liquid) calculations. I always use an online calculator like soapcalc but really wanted to know all the ins and outs.

So here is my calculation based on 1000g Olive Oil
example.
1000 x 0.1353 SAP for Olive Oil = 135.3 lye amount

135.3 x 0.38% as used by soapcalc = 356.05

Total lye solution 356.05 - 135.3 = 220g of liquid.

obviously there is no superfat in my calc and I removed the % from soapcalc.

My question is why is the water value in soapcalc coming out at 380g?

thanks for any help with understanding this.

I don't see that when I run that through SoapCalc. Maybe you did not refresh the browser page? I've noticed that sometimes when I make repeated changes in SoapCalc that the results get wonky. So I clear all settings and start again, and it corrects itself. (Another reason I no longer use SoapCalc.)
This is the result I get with 38% Lye Concentration and 0% SF in SoapCalc:

 

[Kerrie28]

I don't see that when I run that through SoapCalc. Maybe you did not refresh the browser page? I've noticed that sometimes when I make repeated changes in SoapCalc that the results get wonky. So I clear all settings and start again, and it corrects itself. (Another reason I no longer use SoapCalc.)
This is the result I get with 38% Lye Concentration and 0% SF in SoapCalc:

View attachment 62495

Thank you. That is probably what I did wrong. I’m going to go and do it again.

Thank you. That is probably what I did wrong. I’m going to go and do it again.

I figured it out. I didn’t change from water as a % of weight of oils to lye concentration. Silly mistakes. Thank you for responding fresh eyes on something helps you see your mistakes.

 

[SoapDaddy70]

If you are coming up with 380g of water then you are not using the setting for Lye Concentration and/or Water/Lye ratio. You are using the default setting of water as a percentage of oils. 1000g of Olive Oil with 38% default setting of water as a percentage of oil will give you 380g of water. 38% of 1000 is 380.

 

[Kerrie28]

If you are coming up with 380g of water then you are not using the setting for Lye Concentration and/or Water/Lye ratio. You are using the default setting of water as a percentage of oils. 1000g of Olive Oil with 38% default setting of water as a percentage of oil will give you 380g of water. 38% of 1000 is 380.

Yes I’ve just realised that. Lol. Thank you for responding though. I’m just happy my math was correct thought I was going crazy.

 

[ResolvableOwl]

I see you figured out by yourself, but I don't want to let this stand as-is:

135.3 x 0.38% as used by soapcalc = 356.05

You have divided the percentage, not multiplied it. You did the right thing, but wrote it in a weird way.
135.3 / 0.38 = 356.1
In math speak, this means: 135.3 g lye are 38% of the total lye solution. So to find out which weight of lye solution contains 135.3 g NaOH, we divide this by the percentage. The 356.1 g are the total water phaseweight, i. e. NaOH + water. This number doesn't obviously appear in SoapCalc output, but it is hidden within the total batch weight (easily seen in your example because oils are exactly 1000 g).

Another detail that you did intuitively right, but wrote wrong, was percentage notation: “0.38%” is mentioned nowhere. It's either 0.38 (without percent sign) or 38%, which are identical. All the percentage calculations lose their horrors if one just always applies the simple formula 1 = 100% every time one wants to introduce or get rid of a percent sign.


I'm taking this time to encourage people to at least try to do the math by themselves. Soap calculators are immensely helpful tools, but they aren't magic, and are sometimes wrong. A grounding in reality can't hurt from time to time, to not become too dependent on technological black boxes.

 

[DeeAnna]

It's really confusing to use the word "lye" alone in this thread, because people are using this one word to mean two quite different things -- the solid alkali NaOH (sodium hydroxide) as well as the liquid solution of NaOH and water (aka lye solution).

Lye, as a strict definition, is the liquid mixture of any alkali and water. Properly used, the word does not refer to solid alkali, and it is not limited to only NaOH.

When the discussion is so specific, as it is here, spell things out in an unambiguous way -- say "NaOH" not "lye" and say "lye solution" rather than "lye".

Auntie Clara has a nice tutorial on hand calculations that might be helpful -- Lye Calculation Using a Saponification Chart - Tutorial

 

[Kerrie28]

I see you figured out by yourself, but I don't want to let this stand as-is:

You have divided the percentage, not multiplied it. You did the right thing, but wrote it in a weird way.
135.3 / 0.38 = 356.1
In math speak, this means: 135.3 g lye are 38% of the total lye solution. So to find out which weight of lye solution contains 135.3 g NaOH, we divide this by the percentage. The 356.1 g are the total water phaseweight, i. e. NaOH + water. This number doesn't obviously appear in SoapCalc output, but it is hidden within the total batch weight (easily seen in your example because oils are exactly 1000 g).

Another detail that you did intuitively right, but wrote wrong, was percentage notation: “0.38%” is mentioned nowhere. It's either 0.38 (without percent sign) or 38%, which are identical. All the percentage calculations lose their horrors if one just always applies the simple formula 1 = 100% every time one wants to introduce or get rid of a percent sign.


I'm taking this time to encourage people to at least try to do the math by themselves. Soap calculators are immensely helpful tools, but they aren't magic, and are sometimes wrong. A grounding in reality can't hurt from time to time, to not become too dependent on technological black boxes.

Thanks for your feedback. I like to find out what the method behind things, it’s so easy now to just rely on technology and not use your brain.

 

[Kerrie28]

It's really confusing to use the word "lye" alone in this thread, because people are using this one word to mean two quite different things -- the solid alkali NaOH (sodium hydroxide) as well as the liquid solution of NaOH and water (aka lye solution).

Lye, as a strict definition, is the liquid mixture of any alkali and water. Properly used, the word does not refer to solid alkali, and it is not limited to only NaOH.

When the discussion is so specific, as it is here, spell things out in an unambiguous way -- say "NaOH" not "lye" and say "lye solution" rather than "lye".

Auntie Clara has a nice tutorial on hand calculations that might be helpful -- Lye Calculation Using a Saponification Chart - Tutorial

Thank you for your feedback I will definitely keep this in mind in the future. Much appreciated