Blue Aspen Originals

aspen leaf
Fine soaps hand crafted in small batches

How to Rebatch (Handmill) Soap

The most common reason a person would go through this process is to save a batch of soap that didn't turn out right using the cold process method. Some people prefer to rebatch, or handmill as it is also called, in order to add ingredients that would be lost to the lye in the cold process method such as benefits of essential oils, emu oil or oils with special herbal infusions. Another benefit is you can keep a large batch of plain soap and customize small batches from it that are ready to use. Colors that might get eaten up by the lye are safer to add during rebatching as well. I feel rebatching soaps gives the bars a different look than cold processed soap, they are not as smooth and sometimes you can see bits that have not fully melted down.

I have rebatched soap that I forgot to add an oil to when I was making it, one that the fragrance oil siezed the batch when it was added and some soap that did not turn out as planned. When you are rebatching a messed up batch of soap you are able to correct mistakes like forgotten oils or to try and even out a batch you added too much oils or lye to if you can calculate how much of the missing ingredient is needed.

There are 3 ways to melt down the soap in rebatching; microwave, oven and double-boiler.

1. The first step is to process your soap into small pieces. I find that using a grater to grate the soap up works well. Some people also use a Salad Shooter or food processor and shred the soap similar to grating cheese. If the batch you are rebatching is fresh this goes very quickly. I just grate it up into my stainless steel soap pot or pyrex depending on the amount I am rebatching or method I choose to remelt the soap.

Rebatching equipmentThe bars of soap that didn't turn out right, cheese grater, stainless steel pot, a little oil to add and some more fragrance oil. This batch of soap was very brittle and developed cracks all the way through the bars. I was experimenting with different amounts of stearic acid in the recipe.

Shredded soap

The soap is now shredded, took about 5 minutes for the 3lb batch. I have 2 oz of olive oil to add to this batch to try and get it less brittle. The addition of 2 oz olive oil will superfat the finished soap at 9%, that's not too high.

2. For 2 week or older soap only The next step is to add a little milk or water to the shredded soap if the soap is older than 2 weeks and has been sitting out to dry. I prefer to add milk as it seems to allow the soap to melt smoother and also doesn't suds up the soap when you are mixing it around. I generally add 1 - 1½ tablespoons of milk per pound of shredded soap. Then I cover the pot and allow it to set overnight and absorb the liquid. The soap shreds can also be put in a ziplock bag and left for a few days until you are ready to rebatch.

3. Melting the soap. There are several methods to melting down the shredded soap. My favorite and quickest is the microwave, then the oven and very last the double boiler method. Your goal to melting down the soap shreds is to get a thick gloppy almost translucent look to the soap. The addition of heat will speed up the saponification process of the soap if it is newer and not fully cured. This makes it ready to use after it has cooled. After it is melted and before you put it in your molds, mix in the fragrance and additives you want. It will be hard to incorporate in the fragrance as it is a thick gel. Remember it will take half as much fragrance oil than making cold process soap so don't scent it too heavily. The soap will not be liquid thin and easy to pour but rather thick and gloppy. You will have to spoon it into your molds and bang them on the counter to get air pockets out. When all the soap is in the mold I push down on the soap with my gloved hands and bang it around a few more times. If you want you can marble the soap by coloring different portions of it and glopping them into the molds in layers with uncolored or differently colored glops. It won't be finely marbleized as with cold process swirls but it does add color interest to the bars.

Microwave method: this is the quick method for melting down the soap. I use my pyrex measuring cup (or casserole dish with a lid) filled with the shredded soap and microwave it for 4 minutes at a time. Stir the soap as usually it will begin melting and getting a clear look in the center. Microwave for 4 more minutes, stir and continue the process until its completely melted.

Double Boiler method: There are really two methods that can be used in this one. My favorite is to put the soap slivers in an ovenproof baking bag or heavy duty ziplock and boiling that in a pot of water to melt the soap down. This method makes it easy to take the whole bag out of the water and poke at it with oven mits on to stir it up. Then when you are ready to put the melted soap in the mold, just cut a corner off and squeeze it into the mold similar to pipping icing on a cake. Make sure to bang out all the air bubbles. The second method is to use a regular double boiler or a smaller pot inside a larger one. Fill the larger pot with water and put a couple butter knives in the bottom or glass marbles or anything to keep the smaller pot from getting direct heat from the stove. When the water in the large pot is simmering, put the smaller pot in the water so the heat from the boiling water heats the smaller pot and melts the shreds. I have also heard of people using direct heat to melt shreds but I would be afraid of burning or scorching the soap.

Oven method: Preheat your oven to 175-230ºF and move the racks so your large stainless steel pot or casserole dish sits in the middle of the oven and you can pull the rack out to check it periodically. Place the pot with the lid on in the oven for about an hour. Check the soap to see how it is melting and stir it a little. I put it back in the oven and keep checking it every 30 minutes until it is melted and translucent.

melted soapHere the soap has been in the oven for an hour or so. It's fully melted and looks translucent. If you cool a little bit on a gloved finger and touch it to your tongue (tongue test it for harshness) it won't tingle so the saponification process is done. Let it cool a litte and add more fragrance to replace the scent that got cooked off. Stir it up real well and glop it into your mold.

glopping into the moldGlop in the soap and bang it down into the mold really good to get rid of any air pockets. I am just using my regular mold. Since the soap is finished it won't react to metal so you can use any metal molds you have for rebatching as well.

filled moldNow I put my rubber gloves on and really squish the soap down into the mold. And bang it on the counter a few more times, sure scares the kitties.

cover the mold

Here I cover the soap up and let it cool overnight. I feel that keeping the heat in and letting it cool slowly smooths out the soap.

The soap logThe unmolded soap log

Smooth finished bars

These turned out nice and smooth.
Saved that batch of soap!