[bashfulbyte]

I am a soapmaker and have observed something I cannot find the answer to.  In soapmaking there is something called DOS (dreaded orange spots) and it is from the leftover oils in the soap going rancid.  It slowly spreads and can even spread from one bar of soap to another if they are touching.  I have one recipe high in linoleic and linolenic acids.  When this recipe is made Cold Process, without adding heat and molded in such a way that heat cannot build up, the soap will get DOS in a few weeks.  When this recipe is made Hot Process, and the soap batter heated enough to melt the soap (gel), this same recipe will not get DOS.  Why is this?  Is it because the more unstable fatty acids have been destroyed by heat before they can initiate the spoilage chain reaction?  As far as I know, the difference between the melted soap, and the un-melted soap is the way the molecules line up.  I think the molecules in gelled soap line up like a liquid crystal.

[fledarmus]

It is quite possible that the dreaded orange spots are being formed by a mold growing in your fatty acid preparation. The ability of molds to make oils rancid has been known for decades - here is some interesting chemistry from 1928 on detecting the chemical compounds resulting from this action. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1252092/

If that is the case, the hot process is most likely simply doing a better job of sterilizing your oils.

[Zipp]

It's not mold, but is rancidity.  But bashful is quite mistaken that it happens in cold process and not in hot process. And even beyond that, she is mistaken that it appears after a few weeks.

Even if she were correct, It's not likely that it's the heat killing the mold or its spores.  While there ARE molds which can survive very high pH systems, it's unlikely that something that can survive the lye solution that is reacted with the oils will then be impacted by the potential slight difference in temperature that the mixture may experience in CP vs HP (CP still heats up, and gels, as the saponification is exothermic, in HP heat is added to speed up the initial reaction.

What is more likely is that bashful (who isn't very) is changing other variables in her soapmaking.  Different vessels, perhaps, or other equipment or other things.

[curiouscat]

Does the mold have to come with the ingredients? Aren't there spores floating in the air. Would sterilization then help?

Have you tried adding some sort of anti mold preservative? (No idea if they exist)