There are a lot of reasons to rebatch your soap. Maybe you don't like the color or scent. Maybe it separated into a greasy mess or is lye heavy. I always end up with a lot of shavings & end cuts that are not usable as they are, but are perfectly fine soap.
Basic Rebatch
You want to grate up, shave up, or chop up your soap into very small, fine pieces. The smaller they are the easier they will melt. Coconut oil soap, & probably some other extremely hard oil soaps are really difficult to work with in a rebatch. The fresher the soap is, the easier it is to rebatch. So if you have some old coconut oil soap, you have a challenge. If your soap is fresh & ground up finely you can dribble some water or spray some water on it to dampen it & cook, right away. If it is old hard soap you may want to cover it with water & let it soak for a few hours or overnight. Pour the water off. You can save it to add back in later, if needed. I like to rebatch in my microwave in a 2 qt pyrex measuring cup covered with cling wrap, on a low power like 2 or 3. You can rebatch in a crockpot, in the oven, or even in a double boiler. The idea is to dampen the soap to soften it, so it melts faster, & then apply enough heat to melt it. Stir the soap up as it is melting to get a more even melt. Continue to melt until smooth or as lumpy as you like. If the soap starts to get thick before it is melted just add more liquid & stir it in until it is the consistency you want. Then color, scent, swirl. Beautify to your taste & mold.
You do not have to use water in a rebatch, you may chose instead, another liquid like aloe vera juice, a milk, or even a fruit or vegetable juice.
Dry Soap Rebatch
Follow directions for Basic Rebatch, but add a bit of oil, too. This can also be done if you forget your superfat or didn't add enough, & have soap that is drying on the skin.
Oily Soap Rebatch
Check your recipe. If you are sure you added everything correctly, then the soap may have been molded too early or too hot, or in the case of CP, got too hot in the mold & separated. The oily part is part of your recipe so make sure you add all, or as much as you can, back into the rebatch pot. Sometimes a soap will be made with too much superfat that needs to be corrected. his can be done by adding a bit more lye solution. If you know the amount of superfat or extra oils that were added to the soap. Take the amount of lye you added and rerun the batch with a lower superfat in the lye calc to get the new amount of lye. If you added 2 oz lye, and superfatted at 15% & the soap is way too greasy, you want to adjust this. There are a couple different ways to correct this.
1. Run the recipe back through the calculator at the % of superfat you want. Lets say you want 5% superfat. As an example, 2 oz lye gave you 15%, 2.7 oz is what you need for 5% so... you need to add 0.7 oz more lye. Dissolve the lye in at least as much water by weight & add to your rebatch. Heat & stir until you have no zap or pH test is in the normal range for your soap.
2. Make a new batch of soap. Add the shavings of the oily soap to it. If the old batch has a superfat of 15% and you want 5% superfat in the total batch (both combined), then you need to make the new batch at a SF of -5%. You have 10% SF you need to use leaving 5% in the old batch. So making the new batch at -5% will give you 5% in the new batch, too. -5 + 10 = 5. You can adjust the superfat on the new batch to compensate for whatever superfat you need to thin out.
Lye Heavy Rebatch
You will need to add oil and water to this one! If you were unlucky enough to add a lye solution where the lye was not completely dissolved, your rebatch may not be successful. Lye is not soluble in oil so you need water to dissolve the crystals. Once they are incorporated in the soap batter, it can be really difficult to get them to contact enough water to dissolve, or tell they are dissolved, but you can always try. Better than tossing it out! If the lye was dissolved but somehow it is a lye heavy soap, then it needs more oil so that lye can react with the oils you add & complete the saponification. You can add oil to the melted rebatch a bit at a time until it no longer zaps or pH tests safe. Make sure you add even more oil so the soap has a superfat. Unless you know how much additional oil you need, try 1/2 oz ppo (per pound of oil) at a time. Stir it in, give it a few minutes & test, continue until soap tests safe.
