Miscalculating Lye

[mshearn3198]

Recently applied to have EU assessments done by chemists, to make our soap legal to sell. But the response that was given by the chemist about our recipes was that the lye amounts were too high. For example, here's one base recipie.

Pomace oil 225g
Palm Oil 125g
Coconut oil 125g
Castor 25g
Water 165g

We worked it out and got 73 or 74 grams lye, but the chemist is insisting that the most that can be used is 71 grams.

Anyone have any idea where have we gone wrong in calculating the lye?

 

[Obsidian]

Did you calculate a SF into your soap? I ran the recipe through soapcal and with a 5% SF I got 70 grams of lye. With a 0% SF, it was 74 grams.
I would go with the chemists on this on, use 70-71 grams and keep the SF in a safe range.

 

[mshearn3198]

Did you calculate a SF into your soap? I ran the recipe through soapcal and with a 5% SF I got 70 grams of lye. With a 0% SF, it was 74 grams.
I would go with the chemists on this on, use 70-71 grams and keep the SF in a safe range.

Don't do superfatting, so every time we've done the soapcalc the level has been set to zero and we get 73/74.

 

[Obsidian]

Unless you are making laundry soap, you should use a SF. Not only does it help a soap be a bit more conditioning but its acts as a cushion for any variable in your lye.
Since you assesor seems to be figuring a 5% SF, it looks like its going to be required if you want to get approved.

 

[Ford Prefect]

Alternatively, you could analytically determine the SAP of your oil and analytically determine the concentration of your lye and then try to convince the EU chemist that you can make soap with zero super fat because you are working with the actual numbers instead of average values and, even if you are off a little, atmospheric CO2 will neutralize any excess NaOH before the soap gets to a consumer, especially if you agree to age it for 6 weeks or so. Just a thought. You'd have to have a very good QA program in place to make that work.

 

[SaltedFig]

Are you able to enquire as to whether the 5% (that Obsidian observed as being the amount the chemist wants your lye-discount/superfat to be) is a guideline or a rule?

I would be curious to know (with reference numbers to the applicable documents), if you are able to get this information.

Recently applied to have EU assessments done by chemists, to make our soap legal to sell. But the response that was given by the chemist about our recipes was that the lye amounts were too high.

 

[CaraBou]

Why don't you use a superfat - is there a reason?

 

[cmzaha]

Alternatively, you could analytically determine the SAP of your oil and analytically determine the concentration of your lye and then try to convince the EU chemist that you can make soap with zero super fat because you are working with the actual numbers instead of average values and, even if you are off a little, atmospheric CO2 will neutralize any excess NaOH before the soap gets to a consumer, especially if you agree to age it for 6 weeks or so. Just a thought. You'd have to have a very good QA program in place to make that work.

Which is really the only way you will really know the actual superfat. I do not like to superfat but would have to know exact SAP of my oils to truly know so I just superfat low. Although if I use superfat at 2% in soap calc it is usually 4-5% in soapee's calculator. Which proves you really cannot truly know if your oils are not tested for SAP

Why don't you use a superfat - is there a reason?

I do not like the feel of oil in my soap and my drains hate it. I just go with my recipes that are gentle on their own

 

[Ford Prefect]

Are you able to enquire as to whether the 5% (that Obsidian observed as being the amount the chemist wants your lye-discount/superfat to be) is a guideline or a rule?

I would be curious to know (with reference numbers to the applicable documents), if you are able to get this information.

It would be interesting to see whether there is an EU rule on that. When I ran the calculation in soapcalc, I got a lye requirement of 74.01 grams. If the EU chemist is saying a max allowable lye amount of 71 grams, that works out to a discount of 4.067%, but that is based on soapcalc. The EU chemist may have used a different calculator or may have performed the calculation by hand. In any event, I'd like to completely understand the requirements and methodology used for my own future reference.

 

[Mae01]

How do you calculate superfatting by hand in your recipes?

 

[DeeAnna]

The default 5% superfat is a guideline established by tradition and time. There has been no particular magic or science used to determine this number. As Carolyn points out, it is entirely possible to make a reliably safe, mild soap with the superfat quite a bit lower, even without all the analytical testing that FordP is suggesting.

And also consider that the online calcs assume the NaOH purity is 100%, when we know it's really lower than that. The difference between 100% and the actual NaOH purity adds another few percent of "hidden" superfat to the soap, so that apparent 5% might actually be more like 7% to 10%.

My personal soap calculator corrects for the NaOH purity, so my normal 3% superfat is a lot closer to a true 3% superfat than if I used an online calc. I have zero concerns about my soap being lye heavy. Even a superfat of zero to -1% or -2% will probably be fine for most people most of the time if using an online calc -- that will actually result in a neutral to slightly positive superfat. With my calc, I'd run the risk of making slightly lye heavy soap with those settings, based on personal experience, but I wouldn't be too worried -- soap a slight negative superfat will be fine after curing.

And most modern-day commercial soap is made with close to a zero superfat, but the commercial manufacturers do test the soap and handcrafted soap makers generally don't.

That said, the OP may have no recourse other than complying with the assessor's expectation that a 5% superfat is the right number to use. Sometimes that's just the way the world works.

How do you calculate superfatting by hand in your recipes?

Decide on the weights of the fats in your recipe. Use grams as the unit of weight.

NaOH for a fat, g = (NaOH saponification value for the fat) X (fat weight, grams)
Do this for each fat in your recipe.

Add up the individual NaOH weights you calculate. This is your total NaOH weight for the recipe at zero superfat.

Decide on your lye discount (aka superfat) in percent, then --

Total NaOH at a given superfat, g = (Total NaOH at zero superfat) X (100 - Superfat %) / 100

But use an online calc to do all these calculations. It's much easier and reduces the chance of error. I recommend http://Soapee.com

 

[Ford Prefect]

DeeAnna- I'm not suggesting everyone do the analysis, just that, in this case, it might be a way for the OP to overcome the objection. Now as for myself, I intend to perform the tests for a couple of reasons. Like you, I am a long time engineer, so in my wonkish view, performing the tests will be part of the fun, strange as that may seem to 99% of the world. Also, as one of my bosses told me many years ago, "It's nice to be fooled, but it's better to know," which is a view that I've found quite helpful throughout my career. And finally, because of my obsessive-compulsive personality, which others have described by a four letter word much less complimentary, I want to control all aspects of the process at all times, just because I can.

 

[DeeAnna]

And I completely understand your point of view. I just wanted to mention there's a sufficiently acceptable alternative to analytical testing, which is only one way of knowing, not the only way. Most people are not going to break out the reagents and pipettes. I usually give advice that is accessible to the average soap maker, especially if the advice works fine for most people most of the time.

As far as soap makers using the results from their analytical chemistry testing to convince an assessor he/she is wrong, well, I honestly doubt that is going to fly too far. Kitchen chemistry isn't going to be taken too seriously by someone in that kind of job. And if there is a strict procedure the assessor is using to qualify the recipe, that procedure would then have to be reviewed and changed. Not saying it can't be done, just that it won't be easy peasy.