How to Rebatch Cold Process Soap

Rebatching is a great way to “recycle” soap. If you have bars sitting on your shelf that the scent has faded from or an appearance you don’t like, turn it into something new! Here are the steps to rebatch cold process soap in a slow cooker.

Rebatch cold process soap in a slow cooker

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If you are a soap maker, you probably have some soap scraps left over or bars and loaves that didn’t quite turn out how you wanted. Don’t throw them out! You can rebatch and recycle that old soap into something new!

I make cold process soap with raw goat’s milk (click here for my four-ingredient recipe), but you can rebatch any kind of cold process soap. There are different ways to rebatch soap, but I am going to show to you an easy method to do it using a slow cooker. This process takes me between 2 and 3 hours, so plan accordingly.

Table of Contents

Rebatched vs. Regular Cold Process Soap

Rebatched soap can be described as more rustic in appearance. It is difficult to make the top very smooth or do any kind of swirling patterns during pouring, but it is still good soap.

One nice thing about rebatched soap is that it is ready to use sooner than regular cold process soap (which requires a 4-6 week cure time). Rebatched soap isn’t undergoing a chemical change after pouring, saponification already happened when it was first made. Allowing 2 weeks for the added water to evaporate will leave you with a solid, long-lasting recycled bar.

Materials Needed to Rebatch Cold Process Soap

Soap scraps
Kitchen scale
Silicone soap mold
Slow cooker
Cheese grater
Rubber spatula
Mica powder or other colorant (optional)
Fragrance (essential oil or fragrance oil)
Distilled water
Soap cutter

I weigh out my soap scraps before I start so I know how much I need to grate down to fill my mold. I use large, rectangular, 2-pound silicone molds that nest inside pine insulating boxes, but any kind of soap mold will work.

I have a slow cooker that I use just for rendering tallow or lard and making soap. I recommend keeping soap making utensils and appliances separate from the ones that you use for preparing food for your family. The same goes for the cheese grater and spatula.

Grating cold process soap takes a lot of elbow grease. If you’re using a traditional cheese grater, I recommend a flat one that you can lay right over the slow cooker, it’s less messy! What makes the job even easier is a rotary grater that suctions to your countertop.

If you want to make the rebatched soap a different color and scent then the scraps that you are using you will need to add colorants and fragrance. You can use mica powder, clays, activated charcoal, or spices to color your soap. For fragrance you can use your favorite essential oil or a fragrance oil.

If you are opting for fragrance oil, I recommend sourcing from Brambleberry.com. Their products are made especially for soap making and are skin-safe, phthalate and paraben free, and made from superior ingredients. They also have a fragrance calculator you can use so you know how much to add.

Distilled water is used to moisten the melted soap pieces and get the soap batter to a pourable consistency. I use distilled water so that I know there isn’t any bacteria or impurities that could impact my final product.

Once the rebatched soap has cooled and hardened, use a soap cutter to slice it into bars.

Video Tutorial to Rebatch Cold Process Soap

Watch how I use my rotary cheese grater to rebatch cold process soap bars and cut ends of goat milk soap in a slow cooker. See how cool the bars turn out in the end!

Directions to Rebatch Cold Process Soap

With your kitchen scale, weigh out the soap scraps needed to fill the mold. I use about 2.9 lbs.
Use a cheese grater to shred all your soap bars and scraps into tiny pieces and place them in your slow cooker.
Add 4-6 ounces of distilled water to the grated soap and mix with a rubber spatula.
Put the lid on the slow cooker and set it to low.
Every 15 minutes, stir the mixture to keep the soap from burning and sticking to the sides of the slow cooker. The soap should start out the consistency of mashed potatoes, but end up gelatinous.
After about 2 hours have elapsed, most of the shredded soap should have melted down and will be in liquid form. It’s normal for some larger pieces to remain intact, those are fine and will show up as little pops of color in your rebatched soap.
Now you are ready to pour your rebatched soap, but before you do, you can add the colorant and fragrance of your choice. Use colors and scents that will mask the rebatch if that is your goal. I use about 2 teaspoons of colorants and fragrance.
Stir to incorporate the color and fragrance.
Using your rubber spatula, transfer the soap batter from the slow cooker into the soap mold.
Pound the mold firmly on your countertop several times to get rid of any air spaces.
Allow the soap to cool and harden in the mold for 24 hours. I leave it out, uncovered, on my countertop.
After 24 hours, unmold and cut the soap.
Place the bars on a drying rack for 2 weeks.
Use your rebatched soap!