transparent m&p soap

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when i first approached soapmaking, i started by using m&p (melt & pour) soap base. but after conquering the various hot and cold soap processes ["bar soap" - "liquid soap" - "cream soap"], i considered myself a soap "maker", and i didn't feel comfortable using a base made by someone else. there are times, however, when a m&p or a transparent soap is desired. some of the designs featured on my "m&p" page can't be achieved with the usual hot or cold soapmaking process. so, i considered making it from scratch and, after a few setbacks, i finally succeeded in making my own transparent melt and pour base. continue if you want to read my thought on this and how i arrived at this process, but if you don't, skip this part and go directly to "the process" that i use ...which requires no alcohol. -- (now, with this process, and subsequently, the "whipped soap" process, added to the repertoire, i consider myself a "complete" soapmaker.)
the theory

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my initial investigation into this process, revealed a major obstacle; the instructions [from catherine failor's book, "making transparent soap"] presumes that you have access to 95% ethanol (i.e. everclear), which i don't. i live in a state where this and products like it are "verboten".
then, i found this "recipe" for making transparent soap from existing bar soap ...a kind of rebatching. this immediately spoke to me, since it was in keeping with my soapmaking practices -- (i rebatch all my bar soap). accompanying this recipe were the details from several people who'd used ms. failor's book to make transparent soap from scratch.
the "bar soap conversion" recipe is very general, and although the "from scratch" recipes do give some details of the various processes, none give any insight into the procedure, except to simply suggest that it will take some "practice" to get it right. however, the comments from this "glycerin soap" page inspired me give it a try. first, i attempted to convert existing bar soap to transparent (...although, in actuality, i made the bar soap specifically for this process.
after that initial trial [and failure] at converting bar soap, i decided to go the whole route and make it from scratch, since after reading "the book" several times, i could see where converting bar soap and making it from scratch are pretty much the same process.
but, i still didn't have access to everclear, and i didn't want to use the 70% ethyl rubbing alcohol, (which i had used in my first attempts), so, i purchased the perfumer's alcohol from "the chemistry store" as mentioned on my "perfume/cologne" page, this is formula 40B SD ethanol with the only additive being water. formula 40B is 95% ethanol, and with the 10% added water, the end product is 85.5% ethanol, 14.5% water. this approach also produced unsatisfactory results.
this attempt wasn't a total failure since the resulting [opaque] soap was usable, but i'd failed to produce a transparent soap base that could be easily remelted. my difficulties centered around the solvent. even if i did have the proper strength of etoh, the crucial step in this process is "dissolving completely" the cooked soap into the solvent. this requires a considerable amount of stirring and trying to do this while using alcohol only allows the alcohol to evaporate, which rendered the soap less inclined to go into solution. conversely, if you keep the soap "covered" to prevent evaporation, you can't give it sufficient agitation and you still end up with a lot of undissolved soap. i wasn't interesting in either the "plastic tenting" or the other "mixer" option that c. failor suggested in her book. i needed to find a substitution for the alcohol.
i was further encouraged to replace the alcohol because during the curing process, a lot of the alcohol (along with the water) evaporates, making the soap less suitable for re-melting [after it's been cured]. also ...and i'm making an assumption here... wouldn't the alcohol remaining in the soap have a drying effect (?), countering the whole reason for using a glycerin soap in the first place.
in formulating my recipe, i took my cue from the ingredients lists from the last time i bought commercial m&p base. i substituted propylene glycol (which is readily available) for the ethanol. i used the same basic proportions as outlined by c. failor. -- addendum: the supplier, whose ingredients list to which i referred, has since changed his formula and is now using sorbitan oleate (which is also readily available) as the solvent. i suspect this was because propylene glycol, (albeit considered safe for use in many of our foods, drugs, and cosmetics), is a derivative of natural gas, and is not universally accepted. i've not yet done any test with sorbital oleate, so i don't know if it would be substituted in the exact same quantity for the propylene glycol.
being consistent with that ingredients list, i also substituted sorbitol for the sugar, although i suspect sugar would work just fine. again, i based the amount used on the proportions suggested by c. failor. -- most all the commercial bases that list sorbitol as an ingredient make a point of stating that the product does not include any sugars. since sorbitol is more expensive than sugar, there must be some advantage to using the sorbitol, but what? pound for pound, does it cause less sweating ... does it have superior clarifying properties? perhaps [some future] side-by-side comparisons will answer these questions.
the soap, after considerable stirring, all went into and stayed in solution (including all that "soapy gunk" that formed on top). i added the sorbitol solution to the resulting "water-thin" soap, and tested it by placing a few drops on top of a chilled glass bowl. the sample hardened and remained clear. so i went ahead and poured my soap into a form to make one slab of clear* transparent m&p base. -- *because this base is pure soap and has no added detergents, it has a slight "amber" hue; it's not water-white.
after the soap [base] had completely cooled and hardened, i measured off the desired amount, and [very easily] remelted it in the same manner i had with the commercial bases. after incorporating my additives, i molded it, put it into the freezer for one hour, let it rest at room temp for 10 minutes, popped it out of the mold, and voila! i had a beautiful transparent bar.
unlike commercial bases, which have already been cured, this bar can't be used immediately. it has to cure for [at least] 2 weeks. i suspect that i could cure the base for 2 weeks and then, when i formulate it into a bar, that bar would be immediately ready for use.
these conclusions are the results of my intital success with but the one recipe. however, in the future, i do plan to experiment with other oil combinations and different solvent proportions. for now, i'm just pleased to have finally succeeded.
the process

the following outlines my procedure for making transparent soap from scratch and from bar soap: -- (see "soap recipes" for the quantities and ingredients used in these processes.)
select your oils. -- (if you're converting bar soap, skip to step X1)
depending on your preferences, select the oil combination for the batch. the oils typically used to make transparent soap are coconut (10% to 35%), palm (30% to 75%), and castor (15% to 35%) ...and stearic acid.
each oils has its properties and, as with other soapmaking processes, exceeding the limit creates unwanted effects. lard, tallow, or stearic acid can be substituted for the palm oil; palm kernel can be substituted for the coconut oil. if using soft oil substituions (e.g. canola, olive, etc.) for the castor oil, you forfeit some of the soap's transparency as well as requiring more solvent to dissolve it.

prepare lye solution.
the lye amount is determined as usual (using a "lye calculator" -- no discount), and blended with [distilled] water in a ratio of 32.5 : 67.5. this is the same as multiplying your total lye amount by 2.08 to get the water amount.
mix lye water with oils and blend to trace
completely dissolve the lye into the [distilled] water. heat (melt) together all the oils except for the stearic acid -- both the lye water and the oils should be in the same temperature range -- between 135°f and 145°f. aim for the high end for both, since the mixture should not fall below this range during mixing. mix the lye water into the melted oils and blend to trace. when mixture reaches light trace, pour in the [melted] stearic acid and blend thoroughly.
in this particular formula, stearic acid is used [in place of some of the palm oil] to add firmness and hardness to the soap.

the "gel" phase
you now want the soap to go through the gel phase. this is the naturally-occurring phase of the saponification process when the soap turns translucent. you can, however, speed this up by placing the [covered] soap pot in a "bain-marie" (i.e. double boiler) and cooking the soap for 1 [or more] until all the saponification has occurred.
after 1 hour [of cooking], use phenolphthalein to test for neutralization [of the lye], and if necessary, continue saponification.
if you're working with a large enough quantity, you can just wrap the covered pot with a blanket. the heat that's naturally produced by the saponification is sufficient to put the soap into a gelling phase. wth smaller batches, the "double boiler" assures that gelling occurs.

proceed to step 6
X1 start with "clean" bar soap.
"clean" would refer to a soap with no additives, no color, no fragrance, and no superfat. my bar soap would usually have a safety cushion lye discount of 5%, but for this project i'm making a half-pound batch without any superfat -- i'm actually making the "bar soap" specifically for this project.
i prepared my soap in the usual manner using the cpop process, and the next morning removed it from the mold, grated it, and weighed out an exact eight ounces.
X2 melt the grated soap.
i used the double-boiler method for rebatching. i added only a small amount of water (2 tbs.) since the soap was fresh and had not had any drying time. in about 30 - 40 minutes, the soap curls had melted down into a translucent mass.
it's been said that when rebatching soap made with vegetable oils, if you add milk instead of water, the melted soap is smoother and more manageable. since we're aiming for transparency here, [goat's] milk was not an option.

you want to make sure all the soap is melted before proceding. -- proceed to step 6

at this point both the "bar conversion" and "from scratch" processes converge, and the procedure is the same for both.

add the propylene glycol and glycerin to the melted soap. -- (see "the theory" for the addendum on using propylene glycol)
if your soap pot is not already on a double boiler, do so.
mix the propylene glycol (3% - 3.5% of the soap being dissolved ...this is just the fats and lye amounts, not the water.) and the glycerin (this should be 8% - 12% of the finished product), and blend this into the translucent soap. be sure to scrape the sides and bottom of the soap pot to incorporated all the soap into the mixture. stir the soap -- the stock needs to be in the 150 - 160°f range -- until it has all dissolved and the solution is water thin.

prepare sorbitol (or sugar) solution.
only after all the soap is dissolved, prepare the sorbitol solution (this should be 6% - 12% of the finished product) by heating the water to boiling and adding the sorbitol. your solution will be approximately 60% sorbitol / 40% water want to use the least amount of water to dissolved the sorbitol. mix until all (every single speck) of the sorbitol is completely dissolved.
make sure all the sorbitol (sugar) has dissolved. undissolved sorbitol or sugar crystals may cause white patches in the soap as it ages.
before adding the sorbitol solution, you want to make sure all the soap has dissolved. undissolved soap will show as tiny specks in the clear mixture (when a sample in a glass jar is held up to the light). this can cause blooming white patches in the curing soap. if necessary, continue cooking and stiring soap until all the soap is dissolved.

add sorbitol solution to soap.
gently stir the sorbitol solution into the soap, taking care not to create unwanted bubbles.
test soap for clarity
spoon a little of the hot soap onto the back of a chilled glass dish. if the sample hardens and retains its clarity, then you are ready to mold. if it doesn't clear upon hardening, add [in very small increments] more sorbitol solution. re-test after each addition. in the attempt to clear up the cloudiness, be careful to not add too much extra solution as this will cause sweating and stickiness [in the bar] ...and will itself cause cloudiness. this is but one approach to clearing up cloudiness. you could also add more propylene glycol, but too much of this also presents problems -- soft sweating bars.
the propylene glycol, glycerin, and sorbital solutions are expressed as ranges. well, how much do actually you use? you want to use as little as possible, but enough to do the job. this is what's meant by "tinkering" with the recipe. different blends and proportions of oils will require slightly different approaches -- ( e.g. palmitic and stearic fatty acids resist going into solution so formulas with high percentages of palm oil and/or stearic acid may require more solvent for dissolution and clarity).
c failor's book "making transparent soap" covers in much more depth a lot of the situations that can arise and how to troubleshoot them.

pour into molds.
if you choose to scent, color, and add whatever else to the whole batch, you could pour the soap into individual molds. or, as i do, pour the plain soap into a tray mold and, after hardening, cut up and use this plain base as you would any melt and pour soap. the individual bars can be formulated and then cured, or the base can be cured first ...and the resulting bars would be ready for immediate use after unmolding.