Hard oils vs soft oils and speed of saponification

[szaza]

I think a person with a reasonable bit of experience can do a pretty good job most of the time when judging whether a soap is properly made or not. If you've had good results with your soap when you've made it a certain way in the past and you see certain characteristic signs as you make yet another batch, you can certainly use that information to give you confidence that your soap is going to be fine. Going through the gel phase might be a fairly reliable sign for you that all is going well. There's nothing wrong with relying on that experience as a guide.

Hmm... I'm still trying 100 new things and not really sticking with one recipe. There are only 2 recipe's I've tried a few (2 or 3) times and there are always lots of tweaks So I don't think I can/should rely on experience yet

I do still have a question about gel phase.. It came to mind when I was rereading the explanations and I couldn't figure it out on my own.
In your first answer you say that coconut oil is a little bit easier to go through gel than wheat germ oil, all other things being equal. Somehow, intuitively that feels 'logical', plus I've seen the difference with my own eyes. The thing is, now that I know gel phase is a physical phase change, I think I'd (theoretically) expect an unsaturated/liquid oil to gel more easily, since the double bonds /kinks in the chains would prevent a solid crystal structure. Do you have an explanation why coconut oil gels easier? Is that purely because of the extra heat from saponification or is there another (shape/weight related) reason as well? Or is there something that I overlooked or misunderstood?

 

[DeeAnna]

...I'd (theoretically) expect an unsaturated/liquid oil to gel more easily, since the double bonds /kinks in the chains would prevent a solid crystal structure. Do you have an explanation why coconut oil gels easier? Is that purely because of the extra heat from saponification or is there another (shape/weight related) reason as well? Or is there something that I overlooked or misunderstood?

Yes, I believe it is true that soap made from unsaturated fatty acids will go into gel at a lower temperature. I don't have all the phase diagrams to prove this to myself, but looking at the ones I do have, it does look like your thought is correct.

But that's not the only factor you have to consider. Another important requirement that has to be met is the soap has got to get hot enough to reach the gel temperature for that particular soap. Starting temperatures, batch size, water content, rate of heat loss, fatty acid composition, and other factors will affect the maximum temperature that any particular batch of soap will reach. If that max temp is above gel temp, the soap will gel. If it's not, it won't. In general, a coconut oil soap is more likely to get hotter than a wheatgerm oil soap during saponification, assuming all other factors are held the same and assuming the soap isn't being heated artificially.

Basically what I'm saying is you can't definitely predict whether a soap will gel just by knowing the gel temperature alone.