[bar] soap from scratch

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i decided to tackle cp (cold process) soapmaking because unlike the m&p (melt & pour) process in which you're reformulating soap that's already been made, I wanted to build my creation from the basic ingredients. i incorporate hand milling* into this process as this allows me to be more creative with the formulation and design than would be possible with just the cp process.
* the terms rebatching and hand milling are usually used interchangeably, and in lay terms, they refer to the same process. however, in the soap industry, milling means a whole different thing; they grate the soap, and form it by pressing it into shape. also, the glycerin has been removed so it's not as sticky (or mild) as homemade.
a variation of cp is cpop (cold process oven process). this is also referred to as itmhp (in the mold hot process) because it's actually one of the many incarnations of the hot process method. simply put, this method "cooks" the soap [in a warm oven] so that all the saponification takes place and the soap is ready for immediate use ...although some additional hardening may still be required.
(i eventually explored "liquid soap" and "cream soap", both of which can be made from scratch and, like bar soap, can be made using either a hot process or cold process method. to round things out, i sequed into making my own "m&p" base from scratch and a variation of the cp process for making "whipped" bar soap.)

a detailed outline of my procedure [for making cold process bar soap] is as follows: -- (see "soap recipes" for my bar soap recipes)
decide the batch size and determine what oils are being used. the "oils chart" lists the ins and iodine values that are used in formulating a recipe that is balanced and produces a hard bar.
i've decided to work in small 1-lb. batch sizes. this will produce one plain bar (for testing and evaluation), with the rest being grated for milling into 2 to 3 bars with various design-additive-color configurations.
the oils being used for this [initial] soap base are 47% olive oil (to produce a mild, gentle bar), 23.5% each coconut oil (to produce a robust, rich lather), and palm oil (to produce a hard, long-lasting bar), and 6% castor oil (emollient).
if the oil/butter is in solid form, it can be weighed in solid form, unless, like palm oil, it doesn't solidify in a homogeneous state and the fats are not evenly distributed. place the oil container in a hot water bath until completedly and uniformly liquid; then weigh. other solid oils, (e.g. coconut oil), can be heated this way for convenience in handling.
determine and measure out the amount of water. place this in freezer to chill. it is okay if ice starts to form, but do not freeze solid.
when you add the lye to the water --(never add the water to the lye)-- a chemical reaction takes place and the mixture gets hot. for this reason you should never mix lye with hot water, 'lest the mixture "boil over". even with the ice water, the mixture will still get really hot.
in the regular cp process, the amount of water [i'm using] is constant 37.5% of the total weight of the oils.

when making goat's milk soap, one method is to substitute the [liquid] goat's milk for the water. with this method, it's a common practice to freeze the milk into ice cubes or an ice slush before adding the lye. this way, the lye doesn't caramelize (read burn) the milk, consequently producing a honey-colored bar ...although there are those who actually prefer this. see "making goat's milk soap" for more on this aspect of soapmaking ...with my personal results and observations.
using your favorite "lye calculator", determine and measure out the amount of lye needed. cover container and set aside.
there are slight variations in the different lye calculation charts available, so i choose to discount approx. 7% - 8% to assure all the lye is being consumed in the saponification process. this is a safe range since the sap for a given oil is a general value for that oil and may not be the exact sap value of the oil you're using. never calculate below 5% unless you are positively sure of the sap value of the actual oil you have on hand. discounting also adds an emollient quality to the soap, which is a good thing.
note: there is a difference between the an oil's sap value (e.g. olive - 190.0), and the lye factor which is derived from this value (e.g. olive - .1354). don't confuse the two. many sap tables are in fact a list lye factors, (the figure by which the weight of an oil is multiplied to determine how much lye is needed for saponification with no lye left behind in the soap). the formula for converting one to the other is built into the various lye calculators, which all use the same formula, but different sap values, so they may generate slightly different results. it's a good practice to pick one calculator [you like] and used it consistently.
mix in the lye, pouring slowly and stirring constantly until all the lye is dissolved. pour the lye into the cold water ...not the other way around. this mixture will heat up. cover and set aside to let cool to desired temperature.
do this outdoors or with plenty of ventilation, being careful not to inhale the fumes and dust from the lye. lye is caustic. never use aluminum utensils since the lye reacts with it ...use high density plastic or glass. wooden spoons are also not appropriate since the lye eventually corrodes and splinters the wood.
prepare mold(s). if using a tray mold, line with plastic wrap. if using individual bar molds, coat lightly with a cooking spray.
even when using a tray mold, spray the mold so the plastic wrap will stick to the sides and stay in place.
melt solid oils in pot, heating just enough to liquefy. add to other oils. if all liquid oils are used, heat to desired temperature.
you'll want to have your oils and lye/water close to the same temperature before mixing. you can accomplish this by heating the oils, heating the lye (by sitting the container in another contain of hot water), or letting each cool down. you'll want both to be in the 120° f - 130° f range.
note that some recipes don't require the mixtures to be in the same range, suggesting the lye water be at room temperature while the oils are to be in the 120° f - 130° f range.
in any case, you don't want to work at too low a temperature or this may impede the saponification process which, (although it produces heat), needs to take place in a "heated" environment.
when using the cold process oven process (cpop) method , i process with lye water and oils at 100°f. processing at higher temperatures will cause the soap to overheat [in the heated oven] and start to foam. this surface foam layer doesn't ruin the soap, but your soap will harden with an unattractive foamy layer on the surface.

place pot in sink. very slowly pour lye mixture into the oils ...stirring slowly (in a figure-8 motion). once all the lye is incorporated, alternate between stirring with a [plastic or stainless steel] spoon and using a stick blender until mixture reaches light trace.
"trace" is where the saponification is beginning, a point where a bit of the mix drizzled on the surface leaves a trace.
do not use the blender beyond the point of "light trace" or you run the risk of whipping air bubbles into the mixture. these bubbles could result in the formation of pockets of un-saponified lye in the hardened soap. you could do this without the blender at all, but it would take forever to trace. also, don't use the stick blender continuously, 'lest you burn out the motor.
at this point, you would add any fragrance, colorant, herbs, or other additives. i add nothing because i plan to add these other ingredients during the milling process.
finish by spoon stirring to incorporate any additives and to eliminate any air bubbles that may have been created by using the blender.
to employ the hot process method, at the point of light trace, you would place the soap pot in a preheated oven (200°f) for one hour, and stir the soap mixture every 15 minutes or so.
after an hour, your soap should be in "gel" stage and have a translucent appearance. remove the soap pot from the oven and let it sit for 5 minutes or so. when the soap has cooled a bit, you can then incorporate your additives, color, and fragrance. since the soap has saponified and there's no lye present, you can use less fragrance, and any [powdered] goat's milk added at this point won't turn the soap brown.
pour the finished soap into your prepared molds, cover, and let sit for about 24 hours. skip step 8; go to step 9.

pour into mold(s) and let sit undisturbed for 48 hours.
during this period, your soap may or may not go through a "gel" stage, the point at which the mixture turns transparent. there are those whose soap never goes through this phase but still saponifies. gelling is caused by the amount of heat produced by the saponification process in insulated molds, (e.g. large, wooden, enclosed, block molds). this amount of heat isn't generated (and there is no gel stage) when soap is made in individual molds or shallow trays.
should you or should you not insulate your mold (i.e. wrap in towels)? there are proponents on both sides of the argument. in either case, the objective is to prevent the soap from catching a "chill" and shutting down the saponification process. if the room is warm and there are no drafts, there are those who claim no wrapping is necessary. if the room is cold, there are those who suggest wrapping the mold, and placing it in the oven with the pilot light and/or oven light. and there are those who say you should wrap the mold in any case. still, there are those who resort to heating pads, claiming you "can't insulate enough". all boast successful results, so in the end, it's a matter of experience and personal preference.
to use the cold process oven process method (cpop), i place the [unwrapped] oven-proof mold in a preheated oven (170°f to 175°f) for two hours; turn off the heat and let the mold remain in the oven overnight (or 6 to 8 hours). if i'm doing 100% olive oil [castille] soap, i cook it an extra 30 minutes.
some recipes call for higher temperatures (say 190°f) for 1 hour. personal experience will dictate what time/temperature combination works for you. however, using the lower temperatures will allow the use of [certain] plastic molds ...those designed to withstand temperatures around 180°f to 190°f. keep in mind that while saponifying, the soap will get hotter than the oven temperature.

remove soap from mold(s). if tray mold was used, cut the soap into bars.
trays and block molds line with plastic wrap unmold easily. if the soap doesn't want to unmold from individual bar molds, placing the molds in the freezer for 15 minutes facilitates the soap removal.
if this is the end product, skip step 10; go to step 11.
10 if milling (rebatching) is the objective, cut soap into 2-inch cubes, grate, mill. (if soap is still somewhat "soft", let cubes sit for six hours before grating.)
to mill the grated soap, i followed my own special procedure describe in "my rebatch". -- (see "hand milling" for an overview of the different approaches to this process.)
with regard to the additives, colorant, and fragrance incorporated into the base soap, i follow the same [general] guidelines i use for the reformulation of the soap base in the recipes on the m&p "recipes & design" page.
the prepared soap is then placed into individual molds. this mixture is thick and doesn't pour so it'll have to be cajoled into the mold being sure to fill all the space and eliminate any air pockets. i covered the top of the soap with plastic wrap and use the back of a spoon to force it down into the mold and smooth out the top.
let the soap cool and then unmold, freezing for 15 minutes (if necessary) to facilitate unmolding.
11 let finished bars sit on rack to cure. (see the "curing times" for this and other soapmaking processes)
this curing process has two functions. the first is to allow all the excess water to evaoprate leaving a hard, dry. long-lasting bar. the second is to allow any remaining lye to finish saponifying the oil. a six-week curing period is plenty to assure all the lye is gone, but you can still test the bar with a ph strip.
not all ph strips are equal; different kinds give different results. see "ph strip comparisons" for a clarification of the types and use of ph strips for testing your soap.
since most of the saponification has already taken place, you can test your soap as soon as it comes out of the mold. there will be some addition saponification that occurs during the long curing process, but not that much. this way, you can see if you're in the right range. you don't have to wait 6 weeks only to find out that something has gone wrong.
i was surprised to learn that some [seasoned] soapers test with their tongues (ewww!). if they experience a tingle, or what is referred to as a "bite", the soap needs more curing.
12 tah-dah!

"plain (base) soap"

"milled soap"
this "milled" example is the plain base re-formulated with goat's milk, honey, gel colorant, and fragrance, in a rectangular mold with a victorian surface design.
see "my rebatch" for other examples of rebatched soaps.