How To Make Hot Process Soap in the Microwave

Making soap in the microwave is a great way to make a small batch of hot-process soap. It’s probably not any more dangerous than making hot processed soap with any other method. However, I must make some necessary warnings and cautions before we begin. This method is an advanced soapmaking technique, and should not be attempted by anyone who is not familiar with cold-process soapmaking, or anyone who is not prepared to watch the microwave continuously while the soap is cooking inside! I made my entire one-pound batch of soap in about an hour. Watching the microwave took about 10-15 minutes. Please read through the entire tutorial and familiarize yourself with the process and photos before you begin.

Formulating a recipe: I use my regular soap recipe, and calculate a one-pound batch using Soapcalc.com. This is a great size because it is small enough to fit inside the microwave (must have room for expanding soap), and large enough that I can still submerge my stick blender. I use the water amount recommended by Soapcalc, which is 38% of oils.

Equipment needed:
The same equipment you normally use for making soap is what you will need to make soap in the microwave. Since you’ve made soap before, you know what this is, right? The only thing that is different for me is that I use a 64-ounce pyrex batter bowl to melt the oils, and mix and cook the soap. You must have a bowl that is clear so you can see the soap climbing inside.

Let’s begin!

The first thing you must be acquainted with on your microwave is how to set the power level to 5, or half power. I NEVER use full power to melt the oils, or cook the soap. On my microwave, I have to push “time cook”, then the time, for example: “2” “0” “0” for two minutes, then “power level” then “5” and “start”. Yours might be different.

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The buttons on my microwave


Step 1: Measure and melt the solid oils and butters. Using half power, I melt my oils a minute at a time, stirring after each minute until they are mostly melted. Then I stir until the rest melts, and add the remaining liquid oils.

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Solid oils & butters are mostly melted

Step 2: Measure and mix your lye solution. Mine is a simple water and lye mixture. Be sure to start with cold liquid!

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Lye solution in a plastic pitcher

Step 3: This is the best part about making hot processed soap – you can add the lye solution directly to the oils as soon as it is properly mixed without paying any attention to the temperatures.

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Lye solution has been stirred into the oils with a spoon.

Step 4: Stick blend the soap until it’s too thick to blend any longer. Now it’s ready to cook!

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Soap is at heavy trace

Step 5: Cooking soap in the microwave involves a repetitive process of cooking, watching, and stirring. With a one-pound batch, I start cooking the soap in the microwave for two minutes at half power. Since different microwaves cook differently, you will have to watch your soap carefully the first time you make it in the microwave. This is what my soap looks like after cooking two minutes at half power, and stirred down:

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Soap after cooking for two minutes in the microwave.

Then I cook it another two minutes at half power. The soap was still actively bubbling when I took this photo:

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Soap is bubbling up after the second two minutes of cooking

Step 6: Continue cooking, watching, and stirring. I set the time for about five minutes at half power – BUT I DON’T LET IT GO THE ENTIRE TIME. Watch. When the soap looks like the photo below, OPEN THE DOOR OF THE MICROWAVE IMMEDIATELY AND STIR. (You don’t have to let the soap get this high to open the door and stir it down. This was getting precariously close to volcano stage!)

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View through the microwave door of the soap bubbling up.

Stir down the soap each time it bubbles up. This photo shows the “applesauce” stage, where there is a bit of separation. You can see some liquid, and the solid parts are little balls of soap:

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Stirred down soap

Continue to cook, watch, and stir.

Time saving tip: If you just open the door of the microwave and don’t hit “stop/clear/off” each time, then you can just put the soap back in the microwave and hit “start”. You won’t have to re-set the time and power level each time. If the time is running out, I hit the “add 30 seconds” button a couple times to keep it going.

When the soap is mostly translucent after stirring it down, it’s done! The soap will hold together and the consistency is like mashed potatoes. (This process varies each time I make soap in the microwave. This time it took about 2-3 times of cooking and stirring down before it was done. Sometimes it takes a lot more. If you find that the soap is bubbling up after just a few seconds in the microwave, it probably has plenty of heat and just needs to be stirred longer.)

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Mostly translucent soap

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Close-up of mostly translucent soap

Step 7: Add color and fragrance. I didn’t add fragrance to this particular batch. You will want to test the temperature of the soap and know the flash point of your fragrance before adding it, so it doesn’t burn off. As a general rule, you will use less fragrance for hot processed soap than for cold processed soap. If you normally scent your CP soap at 0.8 oz per pound of soap, you can back that off to about 0.5 oz. per pound. I add colorants at the same rate as cold processed soap.

This is going to be plain RED soap:

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Red colorant added

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After red colorant is stirred in

After the fragrance and color is mixed in, you can mash the soap into your mold and let it sit overnight. You may be able to cut it the next day, but if it’s still soft, you might have to wait a little longer. When I make soap balls, I let the soap cool in the bowl, then scoop it out with a spoon and form balls with my hands. I can get consistent sizes by weighing soap pieces on my scale before I form them.

Technically, hot processed soap is ready to use right away. You may want to let it cure out some of the excess liquid if it’s still a bit soft. However, if you’re planning to make soap balls to put in another batch of soap – it’s ready as soon as the balls are rolled!

Any questions?