Soapmaking: If the ONLY fat you have is chicken fat or fish oil, which would be better? Petroleum oil?

Question

I'm writing fiction and this is all they have available. Don't give me references on soapmaking. I just want to know which one would make a better, less objectionable product, because they need to make soap and that's all they have to work with. It's not just for bathing, but for clothes laundry.

Also, will petroleum saponify? I wouldn't think so, but I wanted to ask those who might know with certainty.

Thanks to all who answer.

Answer 1

With many apologies, petroleum (mineral oil) will never saponify. This is because fats and oils are esters of long-chain fatty acids and glycerol. Soaps are sodium salts of fatty acids. In Colonial times, people boiled fat of whatever in water to which they had added ashes. Ashes contain sodium and potassium carbonates and hydroxides. The highly alkaline ashes hydrolyzed (saponified) the fats/oils. In colonial times, soaps would most likely have been made from beef fat or lard, not chicken fat. Fish oil would not have been an obvious choice.

Answer 2

Petroleum definitely saponifies, that's what they use to make the soaps for wheel bearing grease. Yes, soap for grease. Grease is just an emulsion of oil in a relaitvely insoluble soap. I wouldn't wash my hands with it though :)

Chicken fat or fish oil will work, though both will be a bit stinky. The chicken fat would have to be clarified first to get a good product. The fish oil soap will be very soft but again a bit stinky.

Answer 3

Oil and fat carries flavor and fragrance - so I think most folks would not appreciate the fish oil. Plus stronger scents are harder to mask with other fragrances.

Most soap is made from a petroleum-based process for just this reason. It is easier to control and eliminate impurities. However most ordinary folks lack a petrochemical refinery, so if I was making soap I would definitely use Chicken fat, over fish fat.

Oil is no good for soap, it has to be the actual fat.

Answer 4

Lancenigo di Villorba (TV), Italy

Soapmaking are chemical processes able to convert some Fatty Substances in Anionic Stuffs.

ABOUT FATs
Usually, people use the term "FAT" to refer to Animal Fats, e.g. mainly they result TriAcylGlycerols. The latter ones are Glycerols-Derivatives, in effects the processes described release Glycerol itself as an alcohol besides SATURATED FATTY Acid's Salts.
Animals are NOT the lonely source of TriAcylGlycerols : human body itself contain TriAcylGlycerols ; Coconut and Olive contain Fatty Matters Glycerol-based.
In the usual definition, "OILs" are Fatty Matters showing fluid properties at room temperature. Their molecules are NOT based on Glycerol, there is another alcoholic stuff besides to POLY-UNSATURATED FATTY Acid's Salts.
PETROLEUM is a mixture of hydrocarbons, essentially saturated hydrocarbons or Alkanes. Thus, it is clear it contains NOT Esters or Fatty Matters other than Alkanes.

NUCLEOPHILIC SUBSTITUTION
I speak about reactions well-known as "Nucleophilic Acylic Substitutions", e.g. a Reaction's Class where a Nucleophilic Reactive (e.g. Oxydril Ions) lead Nucleophilic Attack on an Electrophilic Substrate (e.g. Acylic Carbon in Ester). The Nucleophilic Attack involve the breakdown in the Acylic Derivative, so the latter one begins to form a NEW Covalent Bond to the Nucleophilic Reactive while it lose the Losing Group which was retained in an OLD Covalent Bond

R'-COOR''(l) + OH-(aq) ---> R'-COO-(aq) + R''-OH(l)

As you can see in the upperstanding scheme, Esters become a mixture of Organic Acid's Salts and Alcohols.
These processes result usually SLOW ones, since you must operate in aqueous media enriched in alkalies and in warm-bath conditions.
I ADD ANOTHER NOTE : if you use KOH then you may concentrate the alkaline solutions retrieving SOFT SOAPs, that are SOAPs maintaining its fluid nature. Elsewhere, NaOH lead to HARD SOAPs because the latter may overcome to its solid state.

CONCLUSIONs
ANIMAL FATs result mainly constituted by TriAcylGlycerols : SoapMaking Processes in Alkaline Baths lead to Glycerol besides SATURATED FATTY Acid's Salts. If you use KOH you may obtain SOFT SOAPs while NaOH lead to HARD SOAPs.
OILs result mainly constituted by Grease Matters other than TriAcylGlycerols, nonetheless they contain Glycerol : the alkaline processes may release Glycerol besides POLY-UNSATURATED FATTY Acid's Salts.
I think these FISH's Derivatives are unappropriated in Soap's Industry.
PETROLEUM is a Latin word meaning "Stone's Oil". It exists another Latin word, e.g. PARUM AFFINES interesting Petroleum and the most common Saturated Hydrocarbons. "Parum Affines" means "Matters few similar", a concept related to Chemical Inertia versus Acids and Alkalies. You cannot use Petroleum and Derivatives.

I hope this helps you.