Sometimes when I want a new recipe, I browse handmade soaps on Etsy for inspiration. I always like the look of hot processed soaps the best, and my favorite often turn out to be salt bars. They have a pale marble look I find lovely, and I’ve been meaning to try my hand at a recipe for ages.
The salt is supposed to contribute to a harder and longer lasting bar, as well as provide exfoliating and moisturizing qualities. And healing. Everything in homecrafting supposedly has healing powers. As with all the other folklore, take it with a grain of salt. Heh heh. See what I did there?
If I’m being honest, I might just like the look and the concept of salt bars. In any case, I did four separate batches: one cold processed; two hot processed and made with distilled water; and one hot processed and made with beer. The results were great, I love the bars I’ve tried so far, and the following is how I did it.
What Type of Salt? From what I can tell, you can use any type of salt you like, table salt, sea salt, Himalayan pink, fine, coarse, kosher, whatever.
But not Dead Sea Salt.
Apparently, Dead Sea Salt contains a lot of other minerals, which have a tendency to turn the soap into a weepy or gooey mess.
I haven’t seen any recipes where people use Epsom salt either. Since it seems to have minerals other than what’s in regular salt, I wouldn’t recommend it.
For my first batches, I used coarse grained Sea Salt that I bought at the grocery store.
How Much? The range I have seen is from 50% of the total oil weight up to 100% of the total soap weight (oil plus liquid plus lye). I chose to try 100% of the total oil weight in my first batches because I had read that less than that sometimes turns out too much like an ordinary soap bar.
How To Size the Recipe to Fit a Mold? In Part II of my original soap tutorial, we went over how to fit your batch to your mold. This link has additional methods for sizing a batch of soap to cylindrical or irregularly shaped molds. Briefly:
For a normal square or rectangular mold: 1) calculate the volume of the mold in cubic inches by multiplying the length by the width by the height; 2) multiply the resulting volume by .40.
So if your mold has a diameter (width) of 4 inches, its radius is 2 inches. 2 squared is 4. Multiplying that by pi (3.14) = 12.56. Times 12.56 by the mold’s height (length) in inches. Multiply that result by .40.
For an irregularly shaped mold: 1) fill the mold with water; 2) measure the water in ounces (an ounce of water by volume is also an ounce by weight); 3) multiply that number by 1.8; this is the cubic inches of the mold; 3) multiply that number by .40.
As I have said before, the numbers that result are your total oil weight in ounces. You don’t have to worry about accounting for the lye and liquid. Either room for the lye and liquid is already accounted for in the calculation or those components fill space between fat molecules in a way that does not increase the size.
But what about the salt? We’re adding (potentially) 100% of the oil weight in salt. Won’t that substantially increase, perhaps even double, the size of the batch?
Here’s the part where you have to get a little bit experimental. As you can see on this LovinSoap.com tutorial, you can just play around with the numbers until you get something close to your mold size.
If you want to be more scientific, figure out the percentages of the total that each component (oil, liquid, lye and salt) comprises. Derive them by running the recipe through SoapCalc for any size batch (the percentages will remain the same) being sure to add in the salt you intend to use. For the recipe that I made (using salt at 100% of oil weight), they worked out like this:
Oils 40%, Liquid 15%, Lye 5%, and Salt 40%. Using those numbers, if you have a 5 lb. mold, your oil weight needs to be 40% of 5 lbs. in order to accommodate the 40% of 5 lbs. that will be filled by adding the salt.
I hot processed all but one of my salt bar batches. Hot processed soap mixture is so fluffy that adding salt did not increase the size of the batch in the way you might expect. In fact, the visible volume of the cooked soap did not appear to increase at all when the salt was added. It just got denser. Not bigger.
That being said, it did add a small amount of volume. I had just used the normal amount of oils that I would use to fill one of my 1.9 lb. molds. I had other molds on standby in case the salt made me go over. It did, just not by much. I couldn’t get the whole batch into one 1.9 lb. mold. But nor could I come anywhere close to filling a second one. The overflow amounted to about one thick bar of soap.
NOTE: I did make one batch of cold processed salt soap. Cold processed soaps are molded before going through the fluffy, expansive phases of hot processing. So I could see how adding salt at that pre-expansion point would make the recipe bigger. But then again, no one takes hot v. cold processing into account when sizing batches. I used a slab mold that was plenty big to handle any extra depth contributed by the salt, but I can’t say I noticed any difference in the size.
The best I can say is play around with your numbers, stick with small batch sizes at first, and keep standby overflow molds on hand until you get a feel for how the added salt affects the volume of your batch.
What Method of Processing? To briefly review:
In cold processing (CP), being mindful to keep the temperatures of the components low (say under 100 degrees F), you combine them without any added heat; blend until they have reached the point of “trace” (emulsification); mix in any additives, including salt, hurrying to keep the soap from reaching the next stage of saponification; and pour the mixture into the mold. Ordinarily, you would unmold it the following day and cut into individual bars if necessary (it still has to cure for awhile before it is safe to use). With salt added, you will need to unmold it more quickly, potentially within an hour of pouring into the mold, so that it doesn’t get too hard to be cut.
NOTE: As explained in this discussion of “trace” at the SoapQueen blog, in cold processing, additives may be blended at the point of a thin trace and the soap molded while it is still a smooth, easily pourable consistency. Alternately, it can be stirred further to the point of a thick trace, which allows for various decorative techniques. I believe the main allure of cold processing is those various decorative techniques.
With hot processing (HP), you don’t have to worry as much about the temperatures of the components; you are going to cook the mix anyway. You bring the batch to trace the same as with cold processing. Certain additives can be blended at that point (I always add sugar syrup). Then you let it cook. Other additives can be mixed in after the cook, which protects them from undergoing the saponification process. The final consistency of hot processed soap is thick and fluffy. It does not pour into a mold so much as get glopped into one. It does not take the fine details of an ornate mold. It does not permit the fancy techniques that can be used in cold processing. But it is safe to use that day (although it will get harder if allowed to cure).
The vast majority of salt soap recipes and tutorials are for cold processed soaps. Other than the aforementioned Etsy ads, which contained little information about the process used, I could only find a couple of tutorials—mostly by people like me who prefer hot processing so strongly they had to make the attempt.
The big question for me was does the salt have to go through saponification for the concept to “work?” If so, could you still hot process the mixture after adding salt at trace? Was hot processing salt soap even, like, a possible thing?
The couple of hot processing tutorials that do exist all added the salt after the cook, so I decided to go with that. I did one batch of CP to compare (of course, the whole aggravation of CP in the first place is that you have to wait for it to cure before you can even try it). I did NOT try adding the salt at trace and then attempting to cook it. I have no idea if that’s a viable thing.
Which Oils to Use? Technically, you could just add the salt to any old soap recipe. The problem is that the salt acts against the lather. To overcome the lather-killing effect of the salt, it is better to use a recipe designed specifically for that purpose.
One of the bubbliest oils used by soap-makers is coconut oil. Almost all the salt bar tutorials recommended 70-80% minimum coconut oil to ensure the soap still lathers despite all the salt. I chose to go with 80%.
Weighed against coconut oil’s bubbly propensity is the issue that it is considered by many people to be potentially drying. Soaps with high coconut oil content are often heavily superfatted to compensate for this. Most of the tutorials recommended 20% superfat for a salt bar, and that’s what I used.
After playing around with the results on SoapCalc, I came up with: Coconut 80%, Olive Oil 10%, Castor 9%, Mango Butter 1%.
Other Lather-Related Considerations. Besides choosing the oil combination, there are two other tricks (that I know of, there might be more) to maximize lather.
One is to add sugar (just ordinary white table sugar). The usual rate given is 1/2 to 1 teaspoon of sugar per pound of oils used. There are various methods for incorporating it. The one I use is to reserve 1-2 ounces of my total water measurement for the recipe and dissolve 1 t. per lb. of oils into that water. (If I’m using a liquid other than water, I use 1-2 ounces less of that liquid than the recipe calls for and dissolve the sugar in 1-2 ounces of distilled water to make up the difference). I mix it into the batch at trace.
The other possibility I considered was to use beer as my liquid. The best and bubbliest soaps I have ever made are beer soaps. I used to think this was from natural sugars in the beer. A home-brewer friend of mine recently pointed out that there is no sugar left in the final product of beer (also no yeast, which is sometimes cited as the source of the benefit to soap-making). I therefore no longer have any clue as to the chemical explanation for what beer contributes to soap making.
However, I remain convinced that it does add something.
The most profuse compliments I get are for my beer soap batches, and I have personally observed the difference in lather. After my conversation with the home-brewing friend, I considered the possibility that the difference was just a product of my imagination and expectations. However, in cooking the various batches of salt soap for this tutorial, I tried one batch using beer as the liquid. The difference was so pronounced that I have gone back to believing it is real and not imagined.
NOTE: One word of caution about using beer as the liquid. Beer and lye generate an even hotter chemical reaction than water and lye. Not only could this lead to a volcano (of the lye-liquid itself or of the whole mixture after it is added to the oils), but burned beer lye-liquid stinks. The smell will fade from the soap as it cures, but it is better to avoid it altogether; soap cooked with non-burned beer lye-liquid has a distinct and (to me) pleasant scent. It is vital therefore to follow all the precautions for keeping the temperature of the lye-liquid low.
Rather than getting the liquid just on the brink of freezing, I actually let the beer freeze. When it was frozen, I took it outside and set it in a snowbank before adding the lye. The lye instantly melted the frozen beer. I kept it in that snowbank until I could remove the container without having it feel warm to the touch. After adding the lye-liquid to the oils, I had to stay right there at the crock pot as it cooked. It would have overflowed otherwise. I had to repeatedly stir it back down to release heat. At some points, I turned the heat off altogether.
Putting It All Together. I think I mentioned I had decided not to worry about fitting the salt into my mold. I just used the normal weights of all the other ingredients for my 1.9 lb. mold. I didn’t know how much volume the salt would add, so I just kept a second mold on standby for any overflow. The recipe came out as:
Coconut Oil 24.32 oz.
Olive Oil 3.04 oz.
Castor Oil 2.74 oz.
Mango Butter 0.30 oz.
Liquid 11.55 oz. (of which 1.5 were reserved to make the sugar syrup)
Lye 4.21 oz. (20% superfat)
Sugar 1.9 t. dissolved in the reserved water and added to the mix at trace
30.4 oz. salt (equal to the total oil weight) mixed in at the end of the cook
The Process. I followed my usual hot processing method.
- Measure the oils into the crock pot on high to get them melting.
- Measure the distilled water into a container and put it in the freezer to get it cooling.
- When the water is on the brink of freezing, take it outside and put it in a snowbank (or tub of ice water) and add the lye. If you are using beer, go ahead and let it freeze first. Avoid breathing the fumes while mixing the lye and liquid together. Let the lye-liquid cool in the snow bank or ice water.
- When the oils are fully melted, turn off the crock pot.
- When the lye-liquid container is cool to the touch, pour the lye-liquid into the crock pot with the melted oils.
- Mix with a stick blender until trace is reached. Some soapers recommend only turning the stick blender on in brief pulses to avoid burning out the motor. I have never worried overmuch about this, as most of my recipes reach trace quickly. Then again, I have burned out a stick blender too.
- When trace is reached, mix in the sugar syrup made by dissolving 1 t. sugar per pound of oils into some reserved distilled water. Mix with the stick blender until it is fully incorporated and a nice thick trace, re-achieved.
- Turn the heat back on, cover the pot, and set the timer for 45 minutes. DON’T STOP WATCHING. These mixtures can overheat and volcano out of the pot if you turn your back. If it starts to creep up, do any combination of the following: 1) keep mixing it to let some of the heat out and tame it back into submission; 2) turn down the heat; 3) turn off the heat altogether, the chemical reaction occurring generates its own heat and may be enough to cook itself; 4) keep the lid off the crock pot. This is especially a concern if you used beer for the liquid.
- During the cook, the soap will go through different stages. First, it might try to separate a little and you will see separated oils or liquids pooling. Feel free to blend it back together when this occurs (arguably, you don’t have to, but it might make you feel better and will also release some heat). It might look like runny apple sauce during this phase.
Second, it will stop separating and go through a fluffy, expansion phase. This is when it is very likely to overflow the pot if you forget to pay attention. Just follow the steps listed above to deal with it if this starts to happen. It might look like expanding mashed potatoes during this phase.
Third, it will stop expanding and settle down and just cook for awhile. It might look like vaseline or glossy mashed potatoes during this phase.
- Once you’ve reached both 45 minutes and the third phase of the cook, you can test for doneness. There are scientific ways of doing this, using pH test strips or phenolphthalein to confirm a range of 7-10 pH, or you can just do the “tongue test.” Use a tooth pick to swipe up a little of the mixture. Blow on it to cool it off. Spread it over the tip of one finger like warm candle wax. Touch it to your tongue. If it zaps like a battery, it’s not done yet. If it doesn’t give an electrical zap but just tastes like soap, it’s done.
- Turn off the heat.
- Mix in any additives. This will of course include the salt. You could also add colorants or essential oils. You have to work fast here. The more it cools off, the harder it will be to mold into one uniform slab. It will start to break apart into crumbles that won’t stick together.
- Get it into the mold fast, ideally while it’s still quite warm.
- Check it in an hour. With normal hot processing, you let it sit in the mold overnight. With salt, the mixture hardens quickly and may get too hard to cut.
As soon as it feels solid and not squishy to the touch, unmold it. An hour is a good estimate of when this might occur. Now is the time to slice it into separate bars.
- Try it. The bars will harden the longer they cure, but the soap can be used as soon as you like. Take pictures of all those suds so you can show your friends.