The lye concentration experiment

[ngian]

Hello everyone, this is just another soapy observation upon the different water amount that can be used in a recipe and its consequences.

I know this is nothing new and everyone more or less have seen how water affects soap all the way to its production. Kevin Dunn has also made various experiments that someone can read at chapter 21 (the water discount).

So this is my point of view upon different initial soap moistures.

I made two identical soaps 5 months ago with Olive Oil pomace: 50%, Palmolein (Palm oil in mostly liquid form as few of the palmitic FAs are extracted): 25% and Coconut: 25%

They were colored with different pigments so as to easily distinguish their different lye concentration:

28% Lye Concentration: Orange pigment -30drops
40% Lye Concentration: Yellow pigment -20drops and Blue pigment -15drops

They were both CPOPed at 70-80°C for max 1 hour (the 28% was kept less time inside the oven as it had passed the gel phase sooner and easier). I then started to using the scale every day after they were cut so as to examine the amount of water loss.

The 28% Lye Con. was cut after 18 hour when the soap paste was poured in the mold and the bar that I started to examine had an initial weight of 106,8gr that had 23.9% moisture concentration based on the full recipe/additives weight.

The 40% Lye Con. was cut after 8 hours and the initial weight of the bar I examined was 103.1gr that had 15.5% moisture concentration.

This is a graph that shows what was the water amount of each bar through a 5 months period time:

So by the time I first weighted them the 28% Lye Con. bar had 25.5gr of water and the 40% Lye Con. had 15.5gr of water. As you can see by the above graph their moisture concentration was almost identical by the first month of curring. Kevin's graphs show a little bit different information upon moisture concentration on his experiments but he also uses more wider range of lye concentrations than mine (except if I'm calculating something wrong).

By the above observation I feel that soap eagers to release its moisture and each and every soap wants to have the same water concentration at the same "age" and environmental conditions regardless of their initial water amount. It seems that for my case it was needed 1 month so as for those two different soaps to be "moisture calibrated".

I have also noticed that while I was weighing every day my soaps, the environmental humidity was interfering the amount of moisture loss of each soap. If the humidity was higher one day, then the soaps would loose less moisture than when the days had lower humidity.

I don't have a penetrometer so my findings are only focusing on water loss. The soap with the bigger amount of moisture loss has shrank more, affecting the surface and the shape of the cured soap.

(to be continued...)

 

[ngian]

Also the overall size of the bar is affected by the amount of water that it has lost. My wooden molds were around 9cm width (~3,5inches) and as a result the 28% Lye Con. soap's width has come to ~8,3cm (3,2inches):

while 40% Lye Con. soap's width has come to 8.5cm (3.3inches):

So to end with my observations (I don't know if they can help the soaping community at all), I list the things I understood that water among other things can influence:

1. I think that hardness is associated with the moisture amount that is left in the soap bar (by pressing both of them with my finger)
2. Higher environmental humidity than normal affects the soap by releasing less of its moisture.
3. Of course the more water concentration the soap bar has the more that can help it to stay for longer time in the gel state while it will come out of it slowly and thus the soap molecules can create the interesting effect of mottling and streaking as seen on the very first picture of the 28% Lye Con..
4. 1 month is the least curring time it is needed for the soap to reach the amount of water it can normally have in our atmosphere but as time passes by moisture is still escaping giving even a better soap month by month.
5. Lastly the amount of water that is trying to escape from the soap bar by the first month of curring will play a big role in the amount of NaOH it can grab and force it to meet carbon dioxide on our atmosphere instead of the oils.

No cleaning of soda ash was performed on the 40% Lye Con. bar's surface.
Also the 28% Lye Con. bar has its side more curve dent because of its shrinkage.

Just wanted to share my findings with you.

 

[mrsserena]

As a fellow scientist, I find this fascinating! I'm going to try higher lye concentrations now, just for less soda ash.

How does the different concentrations affect trace? Is it hard to get a light trace with the 40% solution?

 

[Muskette]

Mrsserena, I regularly soap at 40% lye concentration and in my experience, it does not affect trace. I stick blend only to emulsion before separating for colors, and soap between 75-85 degrees, so that helps as well.

 

[Susie]

Awesome experiment and article! Thank you so very much!

 

[penelopejane]

As a fellow scientist, I find this fascinating! I'm going to try higher lye concentrations now, just for less soda ash.

How does the different concentrations affect trace? Is it hard to get a light trace with the 40% solution?

I find the higher lye concentration does effect trace. I get less time with 40% lye concentration than I do with 28% even if I take it only to emulsion. So if I am doing a complex coloured soap I will do about 30% lye concentration (that's the lowest I usually go to). With Castile where I just mix and pour 40% lye concentration is fine. I use premixed lye solution so it is cold when I soap - not sure of the actual temp of the oils as I do melt some.

 

[Steve85569]

Thank you for taking the time and going to the effort to document this!
Very interesting moisture loss graph showing the "equalization" of moisture content during the initial curing period. This really points out to me the absolute need for a minimum of 1 month cure.

Thank you.

 

[The Efficacious Gentleman]

I agree with PJ - while it might be more than possible to have enough time for playing with colours etc with a 40% solution, it will be much less time than you would be used to if you tend to use a lower concentration. Using a different strength solution will affect trace. You could do certain things to reduce that impact, of course

 

[ngian]

How does the different concentrations affect trace? Is it hard to get a light trace with the 40% solution?

As already stated above, water is one of the factors that affect trace.

Kenna has already beautifully written here everything about trace:

http://www.modernsoapmaking.com/controlling-trace-in-cold-process-soapmaking/

======================================
Here are the most common factors you’ll encounter:
- The base oils in the formula itself
- The temperature of soapmaking
- The temperature of the room
- The speed and amount of mixing
- The amount of water in the recipe
- The presence of catalysts
=========================================


while I also add one more factor when I teach at the soaping seminars:


- How fresh are our oils (liquid and hard oils or butters) as when they are getting old and especially when they pass their self life, then more fatty acids are released form the glycerol and they are floating free. These, when they meet Lye they saponify instantly causing a speedy trace.

 

[earlene]

Thank you, ngian. Great demonstration.

I also really appreciated reading your info about the effect of older oils on trace. I had not considered that before, but thinking back to some of my very first soaps, it could explain a lot. I was using some oils that had been around awhile, both in my kitchen and in my MIL'S kitchen. I knew some were definitely of questionable age. And I wondered why some of those early soaps traced more quickly than I expected based on my reading.

Regarding lye concentration, I have found that I really prefer the 40% concentration best. But when I switch to 33% or 35% in order to give myself more time for color & swirling detail, I am faced with having to wait longer to unmold and cut.

Seeing your experiment, it brings it home me that it's not only because I can unmold and cut sooner, but also the final soap is actually prettier because it doesn't warp as much.

 

[christost7]

Excellent work πατριώτη , greatly appreciated.

I have settled to 2 "settings" for my soapy projects : a full water when many colors / swirling/ pouring time is needed and a 40% for simpler soaps, all other factors being equal.

Thanx again, greetings from Nafplio !

 

[topofmurrayhill]

Do you have observations regarding the appearance of the soap other than shrinkage? It's hard to tell if the mottling of the orange soap in the first pic is within the soap or just surface irregularity.

When melted soap crystallizes back into curd soap, the different fatty acid salts can solidify at slightly different times. This was used by some old-time soap makers to produce some visual effects. Today we see it most clearly when a higher amount of water helps induce gel and the soap contains an insoluble pigment. Generally we describe it as the crackle effect that appears with titanium dioxide, though it's actually happening with all the pigments.

 

[ngian]

Well while I'm looking better at the soap's surface, these whiter areas that where found on the very first picture, are not visible right now.

The only thing that I can see is that the 28% lye conc. soap is more transparent than the 40% lye conc. It might be for the different pigments used.

But something also tells me that it might be for the more water amount that was used that gave the soap molecules the chance to be organized better & easier during gel phase and thus somehow can be produced more transparent soap. It might also be for the time that the soap stayed at gel phase.

The light beam is more visible on the orange soap, while the green soap seems to be lightproof.