Lye concentration and gel

[penelopejane]

Hi
I have read lots of threads on lye concentration and it seems a lot of people use 33% lye concentration. I've had to rework my recipes because of new molds and new CPCP (CP Cooler Process!) and I need some help please.

I am still confused about whether soap will gel at 33% lye concentration?
Will it gel at 35%?
Will it gel at 40%?

 

[BrewerGeorge]

Depends on the recipe and process. A balanced sat/unsat recipe, soaped at 115F and insulated will gel most of the time at 33%. But silicone molds - especially individual ones - will inhibit that, so will pouring at a very light trace.

 

[penelopejane]

I'm mostly talking about Castile soaped cool in thick silicone log molds inserted in timber and then insulated.

 

[earlene]

Penelopejane, when I want my high lye concentration soaps to gel, I CPOP them. I don't think my recipes would gel on their own because I don't use much CO, which heats up faster.

Another tip is to heat your molds before pouring your soap into them. And to soap warmer.

Is there a reason you are soaping CPCP? I haven't actually seen anything on this - do you have a link or an explanation as to how and what purpose it serves? Just by the name (or is that your name for it?) I would guess avoiding gel was the goal.

 

[penelopejane]

My new molds don't fit in the oven. CPCP is my name for the cooler process
I heat the cooler with an electric blanket to its max (30*C) turn it off. Wrap the soap mold in it, close the lid tightly and leave for 24 hrs.

I'm trying to get gel not avoid it. I'd like to know the highest lye concentration I can go to and still get gel.

Threads I've read said high lye concentration avoids gel - is that right?

 

[toxikon]

If you're using a large loaf mold and a heating pad, I don't think you should have any troubles reaching gel at 33-35% Lye Concentration. That's my normal concentration and I don't use any heating methods to achieve gel. It just does it without a problem! I use a silicone loaf mold inside a wooden support.

 

[kchaystack]

Higher lye concentration just means the soap requires more heat to gel. So any soap will gel if it gets hot enough.

You will just have to experiment to find out what your recipe needs at each concentration.

 

[penelopejane]

Has that been your experience kchaystack?

See Aunty Clara:
https://auntieclaras.com/2014/08/intentional-crop-circles-water-discount-as-a-design-tool/

Aunty Clara says at 41 lye concentration (1:1.43) soap won't gel.
At 29 lye concentration (1:2.4) soap will gel

I know a lot of people here soap at 33% and I was wondering if they knew the cut off point. These new molds are bigger and I don't want to waste a heap (more) soap experimenting. :silent:

Thanks brewergeorge and toxikon that is very helpful.

 

[BrewerGeorge]

Is that is right kchaystack?

See Aunty Clara:
https://auntieclaras.com/2014/08/intentional-crop-circles-water-discount-as-a-design-tool/

Aunty Clara says at 41 lye concentration (1:1.43) soap won't gel.
At 29 lye concentration (1:2.4) soap will gel

I know a lot of people here soap at 33% and I was wondering if they knew the cut off point. These new molds are bigger and I don't want to waste a heap (more) soap experimenting. :silent:

The amount of water impacts what the soap does by itself, but you can always add heat yourself to override that. The more water, the faster the reaction and the faster heat is generated. If the soap gains heat faster than it loses it, the temp will rise. Once it gets to around 170F it will gel. Low water will have a slow reaction and release reaction heat slowly, making it less likely to gel on it's own, but you can still provide outside heat to force gel irrespective of what the soap wants to do on its own. DeeAnna (I think) has said here that it's possible to gel soap after it's completely cooled by heating again, but I've never tried it.

ETA: Things like sugar or certain FO's can also influence how fast the heat is created thus how easily soap gels.

 

[penelopejane]

^^^ Thanks Brewer George. I didn't know temps would override a soaps natural tendencies despite reading all the threads. :cry:
I only know I've cooked soap in an oven at 140*F and it wasn't pretty (it smelt bad forever & had to be thrown out).

 

[DeeAnna]

The temperature in an oven can spike up quite high during the time the burners are on, so delicate items (soap?) can burn even if the temperature setting is low. This is doubly true when the oven is preheating, which is why most of us preheat the oven and then put the soap in, not vice versa.

BG and KC both have valid points.

I agree that most soap recipes will go into gel during saponification if the lye concentration is at or below 28% (aka full water) and very few recipes will go into gel if the lye concentration is at or above 40%. (I'm assuming all other factors are held equal and we're not CPOP'ing or otherwise doing things to force gel.) But that leaves a 12% range of lye concentration between those two extremes in which the soap may or may not gel.

Within this range, the soap may or may not gel, and this variability is partly due to the fatty acid content. The fatty acids affect how easily the soap melts -- goes into gel -- due to the length of the fatty acids and their shape. Soap very high in oleic acid (olive oil; long but twisted molecule) or lauric and myristic acid (coconut, palm kernel; short and straight molecules) is more likely to go into gel at lower temperatures. Soap very high in palmitic and stearic acid (lard, tallow, palm; long and straight molecules) might not gel at all, even at the hotter temps some people use for CPOP.

But most of our recipes aren't so lopsided -- they contain a blend of fatty acids. For example, the fatty acids in my latest recipe are about 50% oleic, 25% palmitic + stearic, and 10% lauric + myristic. This soap often gels when I soap with 31% NaOH concentration, but is not as likely to gel at 33%. I think that's generally true for many recipes based on a mixture of fats, from what I gather from other soapers.

Fatty acid content alone isn't the only control on gel vs no gel. BG pointed out that you can force soap to gel during saponification by adding an outside source of warmth or by insulating to reduce heat loss or both. This is not "overriding the soap's natural tendencies," it's just something one can choose do to the surrounding environment to encourage the soap to gel or not. Soap made in the humid warmth of summer often behaves differently than soap made in winter in cool, dry air. Actively reducing heat loss is not greatly different than accepting these natural swings in the environment.

I sometimes suggest doing a "CPOP after the fact" as a way of fixing soap that didn't gel during saponification. It's not my idea -- just one I try to share when I can. I have monitored soap during a "CPOP after the fact" heating. It does not actually go into that semi-liquidy state we call "gel", but the soap after it cools looks exactly as if it did gel -- it becomes firm, waxy, and translucent.

This observation makes me wonder if the qualities we like about gelled soap is more related to the soap reaching a certain temperature and then slowly cooling. It may make no difference whether it actually gels or not. I suspect this whole heating and cooling process allows the soap structure to become organized more quickly and efficiently. That, not the gelling, is what gives the soap that nice translucency and firmness that many of us prefer.

 

[kchaystack]

Has that been your experience kchaystack?

See Aunty Clara:
https://auntieclaras.com/2014/08/intentional-crop-circles-water-discount-as-a-design-tool/

Aunty Clara says at 41 lye concentration (1:1.43) soap won't gel.
At 29 lye concentration (1:2.4) soap will gel

I know a lot of people here soap at 33% and I was wondering if they knew the cut off point. These new molds are bigger and I don't want to waste a heap (more) soap experimenting. :silent:

Thanks brewergeorge and toxikon that is very helpful.

I was able to get my 40% concentration 100% OO soap to gel. Also, I have made 100% CO soap with a 40% concentration for laundry soap and it gelled with no added heat.

Her soap recipe won't gel at the temps she was using. I am sure at some point if she had added enough heat the high concentration soap would have gelled.

 

[BrewerGeorge]

So DeeAnna, do lauric and myristic gel at lower temps, or do the react easier/faster thus releasing heat faster? Both maybe?

 

[penelopejane]

I was able to get my 40% concentration 100% OO soap to gel. Also, I have made 100% CO soap with a 40% concentration for laundry soap and it gelled with no added heat.

Her soap recipe won't gel at the temps she was using. I am sure at some point if she had added enough heat the high concentration soap would have gelled.

kchaystack when you say "with no added heat" were your soaps wrapped or enclosed in a timber mold/box?

Thanks DeeAnna for the explanation was very helpful, I don't think it had sunk in with me how important the heat factor was.

When I ruined my batch of soap I preheated the oven to 50*C (122 *F or maybe a little higher) but forgot to turn it off and let it cool a bit before I put the soap in. It "cooked" for an hour before I realised my mistake but the damage was done.

 

[The Efficacious Gentleman]

I'm not kc, but my high co recipes get crazy hot in my wooden moulds alone - they are maybe 2-3 cm thick (not at home to measure) but with no other wrapping or anything like that

 

[kchaystack]

kchaystack when you say "with no added heat" were your soaps wrapped or enclosed in a timber mold/box?

Thanks DeeAnna for the explanation was very helpful, I don't think it had sunk in with me how important the heat factor was.

When I ruined my batch of soap I preheated the oven to 50*C (122 *F or maybe a little higher) but forgot to turn it off and let it cool a bit before I put the soap in. It "cooked" for an hour before I realised my mistake but the damage was done.

The CO was in a silicon mold with a corrugated cardboard support.

 

[DeeAnna]

So DeeAnna, do lauric and myristic gel at lower temps, or do the react easier/faster thus releasing heat faster? Both maybe?

The key point is that this kind of soap will go to gel at lower temps. Whether this type of soap also saponifies faster, I can't say for certain, but even if it does, that's not really the issue -- adding insulation or using a CPOP method will compensate for that. What's more important is this soap will go from a solid phase into a gel phase at lower temperatures than other types of soap, all other things being equal.

*** Geek Alert -- science-y explanation follows! ***

Researchers have made soap using a pure fatty acid and then tested the pure soap by varying its temperature and water content. What they end up with after all the science is done is a strange "phase diagram." This diagram outlines the temperatures and water contents where the pure soap is "curd soap" (aka solid soap), where it turns into "neat" or "middle" soap (aka different types of gelled soap), and becomes an isotropic solution (a watery liquid mixture).

The clearest phase diagrams I have are for potassium (KOH) soaps, so that's what I'm sharing below. I don't have a full set of sodium (NaOH) soap diagrams, and the few I do have are from various authors and tend to be harder to follow.

The image below is an excerpt from a larger phase diagram for potassium oleate. This is the soap made from KOH and pure oleic acid. The black angled line on the left shows the boundary between phases -- to the left of that line, the soap is solid (curd). To the right, the soap is a gel (neat). The second angled black line on the right is something I'm going to ignore in this thread, but that one is of interest to a liquid soap maker.

The red horizontal line shows the effect of water content on the soap at a constant temp of 20 C (68 F). At that constant temperature, potassium oleate is curd soap (solid) when the pure soap content is 75% to 100% (meaning the soap contains 0% to 25% water). As the water content increases from 25% and up to about 80% water, the soap changes phase to become "neat soap" or what we call "gelled soap". As the water content increases above 80%, the soap becomes an "isotropic solution", meaning a watery liquid.

The blue vertical line shows the effect of temperature on the soap. Let's take some potassium oleate soap at 80% pure soap (and thus 20% water) and warm the soap in the oven to 75 C (170 F). As the temp rises from 20 C where the soap is in solid form, the soap will shift into "neat" (gel) form about 40 C (105 F).

So the phase diagram for potassium oleate shows there are two ways to make any given soap go into the gel (neat soap) phase -- increase the water content or increase the temperature. Or both. So you can use a lower lye concentration (more water) and/or soap warmer if you want the soap to be more likely to gel.

 

[DeeAnna]

The image below is a similar phase diagram for potassium stearate, the soap from KOH and stearic acid. This soap behaves quite differently than potassium oleate. There is another phase shown called "middle soap." For the purposes of this thread, the middle soap and neat soap phases can be lumped together into what we call the gel phase.

At normal room temperature (20 C, 68 F), this soap is going to stay in curd (solid) form no matter what the water content is. And if the water content is held constant at an 80% pure soap content, it's going to be tough to get this soap to gel even doing an old-style CPOP where the soap is warmed to 75 C (170 F) and held there. This soap will turn into a gel around 100 C (212 F) or hotter.

So you can see that different types of pure soap can shift from solid to gel at quite different temperatures and water contents. Oleic soaps and stearic soaps are examples of the two extremes. The general pattern of "more water and/or more temperature => more likely for the soap to become a gel" still holds true for both types of soap, but the boundary at which this change occurs is quite different for these two soaps.

 

[DeeAnna]

And last but not least, here's a phase diagram for potassium laurate, the soap made from KOH and lauric acid. A laurate soap doesn't want to be a gel any more than the stearic soap does, but it also doesn't much care to be a gel either. There is a small region at the left where the soap is solid, a narrow band in the middle where the soap is a gel (middle or neat soap), and a wide region on the right where the soap is a watery mixture (isotropic solution).

***

So what about real life? What about NaOH soaps which most of us make more often than KOH (liquid) soaps? What about soap made with real, everyday fats, not pure fatty acids?

When you shift the alkali from KOH to NaOH, the phase diagrams for the sodium soaps look roughly similar, but the region in which the soap is solid (curd) becomes larger. This essentially means a sodium soap would much rather stay solid than turn into a gel. It will have to be somewhat warmer and/or wetter to make the shift. The region in which the sodium soap is a gel may also be smaller (again, sodium soaps don't like to be gels) and the region in which it is a watery mixture (isotropic solution) may also be larger.

We don't make soap from a single pure fatty acid; we used mixed fats and every fat is a blend of several fatty acids. The phase diagram for my recipe that's high in lard (high palmitic and stearic acid) and HO sunflower oil (high in oleic acid), for example, might possibly be a rough average of the diagrams shown above for the oleic and stearic soaps.

 

[penelopejane]

The key point is that this kind of soap will go to gel at lower temps. Whether this type of soap also saponifies faster, I can't say for certain, but even if it does, that's not really the issue -- adding insulation or using a CPOP method will compensate for that. What's more important is this soap will go from a solid phase into a gel phase at lower temperatures than other types of soap, all other things being equal.

*** Geek Alert -- science

It took me a while but I actually understand what you are saying, DeeAnna. You are incredibly good at explaining these things clearly to even the most reluctant reader. Thank you so much.

I might just even be tempted to look up a phase diagram for NaOH soap.
Don't go there people! It's a scary Kevin Dunn world out there. Stick with DeeAnna. :mrgreen: