As many already know, and of course others do not, a by-product of heating glycerine to the smoking point is a chemical called acrolein.
When producing soap from the glycerine layer often it will be necessary to bring the glyc to a fairly hot temperature in order to get it all into a liquid form so as to make it easier to manipulate. When the heated glycerine starts smoking it gives off acrolein, which is why when soap making it should always be done in a well ventilated area with no direct air flow into your face. The toxicity of acrolein dissipates once it is mixed into solution and it begins to cool, so there so no concern about the final product being toxic.
The only toxicity concerns that may remain are that of residual methanol in the glycerine,which is why it is important that you demeth your glycerine completely before making soap from it. It makes a fantastic end product although certain care must be taken when producing it so that you get the full benefits of a great product and none of the unwanted residual effects.
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Hi Legal Eagle,
All very good advice. When I made my first soap batch I demethed the glycerol in a pan and it was difficult to know the difference between steam coming off and the acrid acrolein smoke. On my second batch I was careful to keep the temperature at around 90 to 100C; the pan never got hot enough to release the acrolein but all the water and methanol evaporated out after an hour or so.
As an aside, I have just done my first biodiesel reaction using 100% ASM, the main purpose being the creation of sodium glycerol to make my first batch of solid bar soap. Can't wait to get started.
Kind regards from England,
The unwanted residual effects (toxicity) of NOT removing all the methanol from the glyc layer. I am sure everyone is aware that methanol is a toxic substance, or should be. It's exposure is cumulative (builds up) and can cause serious health issues, which is WHY it is so important to be sure it is all removed before you go making soap that you will rub all over your body with it.
Sounds more dire than it is really; with a modicum of care the methanol can be effectively removed and the potential for health problems becomes moot. I covered most of this in The Guide and Lather!, but thought a reminder might be of value.
We have been making soap from the biodiesel glycerine for many years and have not suffered ANY negative side effects of residual methanol exposure 'cause I made sure it was all gone. The soap making process is relatively simple, although none of the steps can be skipped for expediency's sake; the chemicals we deal with are all pretty nasty and should be treated with respect and understanding.
If you are using a hydrogenated oil as your base for biodiesel it will make bar making that mush simpler, but if what you have is canola/rape seed as a base then it will require a binding agent as canola is a short chain oil that will give you a sloppy sticky bar. We use a deodorized lard as a binding agent and it works great; has for years. There are other products out there that will accomplish the same thing although most are either chemical or synthetic in nature. Same with scents; you can get cheap scents that are synthesized (and carcinogenic) or opt for all natural essential oils derived from plants.
How can one be sure all the methanol is removed?
What are the negative side effects of cumulative methanol exposure?
That is what the internet is for. I know the answer, but then I would just end up on a never ending carousel of why's and wherefore's, and I don't want to play.
** Don't tell me who you are, show me what you do and I will tell you who you are.- Jerry Rubin**
Yeah, sure. That's why this comes off as an attempt to sell your book, not share information. Frighten people then offer to lead them to safety.... for a price.
I posed the question "How can one be sure all the methanol is removed?" after an unsuccessful internet search for that answer. It's unfortunate you would rather play games.
Why didn't you fully disclose that important information when you started this discussion?
How to know when biodiesel glycerol is safe to use is a legitimate question I haven't seen answered or discussed. The commonly available information says heat the glycerin to 150 degrees F. to remove any excess methanol, but says nothing about how long to heat it or more importantly how to know when all the methanol is expelled.
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