Hot Process Argument (Chemistry related)

[kharmon320]

Okay, I'm going to jump in here with this ongoing discussion between my husband and me. I'm not sure we completely disagree, but this has been one "hot" topic. There are a couple of separate issues, so I'll list them. If someone can point me to a scientific source to back up the info that would help in my argument with my husband. :wink:

1. He doesn't buy it that HP soap is "ready to use" in 1-2 weeks just because you forced the gel/added heat. I say that the addition of heat causes the process of saponification to occur quicker than without the extra heat. It make sense to me that the heat causes the molecules to move faster and faster, more contact occurs between the various oils/alkali, so there's more reactivity between the particles, correct? I've looked up Caveman Chemistry & some excerpts from Scientific Soapmaking, but couldn't really find the words that the addition of heat actually speeds up the process. He's a proof type of person.

2. If you do CPHP and you do the CPOP, isn't that the same reaction? Are they both usable at the same time? Less cure time? I realize the CPOP may still have more water, but I'm really just referring to the amount of lye in the product.

3. Which leads to... Let's say that I place my CP soap on the counter, insulated and full-gel occurs. Why would my cure time be any different than the CPOP that also gelled? It seems like gel is gel and same reaction takes place. Does the extra outer heat in the oven cause more saponification to take place?

I'm simply trying to wrap my brain around this and curing time. I've always left my soaps to cure for 4-6 weeks. I'm sure I've left out half of what we were discussing. If you made it through this post, thanks!

Kerrie

 

[carebear]

Scattered response - pardon my beer!

Cooking just speeds the initial reaction. Once the heat is gone, the speed of any remaining reaction would slow back down.

gelling reduces the cure time by the amount of time it would take to reach the same point. cooking reduces the time the same way - just gets you to the "start the cure" point sooner by a day or so. you need enough moisture to get the soap into the mold - so that still has to evaporate, and experience tells me that the soap gets milder as well,

It is MY contention that both CP & HP benefit from a cure period. In general, in the first 2 weeks I find that soaps (both CP & HP) get milder. The next 2 weeks are, in my experience, more about allowing more of the moisture to evaporate so the soap primarily gets harder. I do not have proof of the first part, but if I was motivated I could pull up weight loss data for the evaporation part - tho of course the curve will be impacted by the initial amount of water used, the size and shape of the bars, and the ambient conditions in the cure room.

The cure period isn't just about the lye.

 

[kharmon320]

Thanks for taking the time to reply. Everything you said makes sense. I've been scouring the net since 8:30 trying to find the scientific proof about the application of heat to speed the process. I accuse my husband of needing proof, but I think I'm enough of a nerd to need proof also. I would have a hard time giving a way a bar of CPHP soap at 2 weeks without feeling it's 100% ready.

I've tried the CPHP, but don't really like the look of the bars, so was leaning more towards CPOP, but I can't scientifically convince myself that CPOP would be ready to use any sooner than plain ole CP. I think my endeavour at this point will be to use CPOP to force a gel and that's the only reason (not to speed up a cure time).

 

[MissMori]

You could do an experiment to find out. Take the ph of the soap at various stages to determine when saponification ends.

 

[turbo]

For question #1, the external heat does move things along. This reaction for saponification is quite similar to that of biodiesel. the reaction works best at temps of 135 - 150F. I dont excede 150 F due to the boiling point of methanol. The higher the reaction temp, the shorter the reaction time. Reaction time is also shortened with strongermixing( hand wisk or stick blender). The higher temp facilitates letting the lye operate as a catalyst to break off the fatty acid chains then let a hydroxide link up. This is why non gell takes so long to cure. yes the reaction will take place but at a much slower rate.

 

[carebear]

For question #1, the external heat does move things along. This reaction for saponification is quite similar to that of biodiesel. the reaction works best at temps of 135 - 150F. I dont excede 150 F due to the boiling point of methanol. The higher the reaction temp, the shorter the reaction time. Reaction time is also shortened with strongermixing( hand wisk or stick blender). The higher temp facilitates letting the lye operate as a catalyst to break off the fatty acid chains then let a hydroxide link up. This is why non gell takes so long to cure. yes the reaction will take place but at a much slower rate.

true for the time in the pot or oven, but once it's off the heat then it's not accellerated.

 

[Guest]

"Ready to use" depends on the user. For me personally and my soap, it's often the next morning.

I found an experiment on google books, regarding some conference about detergents, where they performed and measured a complete saponification in about 3 hours (at 100 degrees celsius).

The reason to wait for weeks is more about evaporating the water than completing the saponification.

 

[carebear]

There are differing views on this. (Tho I'm hard pressed to believe there are differing truths. )

Trace residual lye continues to react during the cure period, as well as water evaporating. Double benefit.

I don't have my chemistry references here. I'm not sure i have them anywhere available since I've moved, but will look. But in the meantime take a gander at the anecdotal material that abounds.

Or prove me wrong. I love learning.

 

[IrishLass]

I agree with Carebear- that we consider there to be a distinct difference between saponification and cure.

Saponification is when oils are converted into soap. That's what the word 'saponify' actually means- i.e., previously you had a bowl full of messy, oily/greasy fatty acids with no cleansing/sudsing properties, but now you have a hard, solid mass of something that cleanses/suds and washes away grease as a result of adding an alkali. The fact that you are now holding something in your hands that's solid and that cleanses/suds proves that saponification has happened- and, yes, adding heat does indeed speed up the process and get the fatty acids 'there' quicker- but once you're 'there' (which can take as little as a mere few hours) I believe with Carebear that it is only the beginning of the 'start cure point'.

One of the meanings of 'cure' is to 'improve the condition of", and from my experience with my own soap over the past 5 years, 'improved condition' is what tangibly happens to the behaviour of my soap when I let it age. It lasts longer in the shower, is milder to my skin, and lathers more copiously, etc.... A minimum of 4 weeks is what it takes for all these qualities to come together in my soap to my own satisfaction (what I like to refer to as my soap's 'earliest best')- i.e. the point where I'm most proud or least ashamed to offer it to others.

"Ready to use" depends on the user.

This is very true. Because of how different some people's skin-likes/dislikes are, 'ready to use' can vary from person to person. I completely agree, though only with the understanding that we are talking about soap that has ceased to 'zap'. As long as it is tongue-neutral, I say use it as early as your skin is happy with it.

I've lately been reading 'Scientific Soapmaking' by Kevin Dunn, aka, the Caveman Chemist (he's a chemist and a soapmaker, the coveted combo :wink: ), and in his book he explains that 3 things happen during cure: 1) It loses weight due to evaporation; 2) It hardens; and 3) Any left over alkali is neutralized by atmospheric carbon dioxide. He says the reason why cured soap has always been considered milder than fresh soap is because we live in an atmosphere that is slightly acidic in nature, and that when soap is allowed to sit in a well-ventilated area, the acidic carbon dioxide in the air reacts with any residual sodium hydroxide left over- which can actually be as much as 2 parts per thousand in a properly made soap according to Dunn (it seems that 'fully' saponified doesn't necessarily equal '100%' when you get down to the nitty gritty of measuring things on a minute level. :wink: ). Dunn states that if it measures as much as 2 parts per thousand you just need to let it cure longer, and that if it measures as much as 3, it most likely was formulated wrong and you need to go back to the drawing board. One part per thousand or less seems to be the optimal measurement (he tells you how to measure it in his book for those who are inclined). After consuming the residual sodium hydroxide, the acidic carbon dioxide then sets to work on the next strongest alkali- the soap itself, which causes it to feel milder over time.


IrishLass

 

[kharmon320]

Thanks for all the wonderful explanations. I may (for the sake of curiosity) test pH at some point, but otherwise I'll keep researching.

Part of this discussion arose because my husband is itching (like a mad man). I think it's possibly the laundry detergent, but he thinks it's the Orange Patchouli CPHP soap that is causing the itching. There are soooo many different variables that could be the culprit, but it lead to the discussion about the HP soap being ready sooner. It was approx. 2 weeks old when he started using it. The boys and I haven't had any issues with it, but his skin has gotten very, very sensitive since he last used homemade soap (about 3 years ago). So, no he's being "anti-homemade soap" at least until he stops itching. Then he's willing to the try the plain jane Castile soap in at least 6 weeks. No fragrance, no additives. Maybe the coconut oil is irritating him, maybe a different oil. Oh well, this is a completely different topic.

Back to the main topic...I appreciate all the responses!

 

[krissy]

my DH is allergic to coconuts and at first he was fine with the oil in my soap but then he started itching more and more. i gave him a 6 month old bar of castile i had in my soap room and his skin is no longer itching and he is much happier. maybe your dh is allergic to one of the recipes ingredients, or maybe it needs to cure longer, but if you think it might be the soap, then i would suggest buying a true castile from the store and let him use it until your batch cures. see if he stays itchy. if he does, look for something other than your soap as the cause.

 

[kharmon320]

Krissy- Thanks for the info. It just dawned on me that even though it's 85% olive oil soap, there is 10% coconut oil. Guess I need to make a 100% olive oil soap.

I'm leaning toward the laundry detergent because he's really itching more where the clothing touches, but I'm not ruling out the soap either. He's been one allergic mess in the past few years. He absolutely loves the Orange Patchouli (as do many others), but he may need a very plain soap.

 

[carebear]

check your laundry detergent bottle - look for "enzymes" on the label. If they are there (most detergents have them) switch to one that doesn't - I recommend All Free & Clear.

 

[krissy]

Carebear, what do the enzimes do? i know they are supposed to be helpful in getting rid of stains? or dirt... but why would they make a person itch?

 

[carebear]

people can be allergic to them. my kids are - when we use detergents with enzymes then when my son takes his shirt off it looks like he's still wearing one that's bright red.

 

[krissy]

people can be allergic to them. my kids are - when we use detergents with enzymes then when my son takes his shirt off it looks like he's still wearing one that's bright red.

wow! that sounds painful. poor DS

 

[kharmon320]

Thanks for all the tips. My husband did admit last night that the itching is only where his clothing is touching (and also where he sweats more). It's been very, very hot while he's working (in a manufacturing plant). Another thought is a heat rash or the sweat is making him more sensitive to the detergent. He does have a faint splotchy, pink rash all over torso.

He said, "It's probably not the soap, but we'll see". It stinks when the whole family has sensitive skin.