Hot & Cold Process Soapmaking- What’s The Difference?

[Hot process overview starts at 3:41]

Hot process soap making and cold process soap making can use the same ingredients and the same recipe but have different processes for making them.  First I’ll tell you about the long process of cold process soap and then I’ll let you know why I prefer hot process.

In cold process soap, the oils and lye solution are mixed separately, with the oils in a double boiler on the stove.  Then you must bring them to a similar temperature- it has to be within 5 degrees of each other, usually between 105-120 degrees F; then they can be mixed.  It can be a hassle trying to get them to the same temperature at the same time- with additional heating or ice baths. 

Once the soap is colored, scented, and molded, it has to be set in a specially curated place overnight to try to make the soap go through a gel phase.  The gel phase is when the soap becomes gelatinous and translucent and it heps the colors come out nicely.  The soap has to be in a warm place, often insulated with towels and a cardboard tent over the mold.  But it can’t be too hot or it can crack and it can't be too cool or it will not have the same colors throughout the bars. 

And after about 48 hours, you hope it comes out of the mold nicely.  Otherwise, you leave it longer until you can unmold it.  After it's out of the mold, wait another 48 hours, and if it’s dry enough, you can cut it. 

And then it needs to cure for 4-6 weeks (so the lye completes the process of saponification and is no longer caustic) and you need to flip it every 4-6 days during those 4-6 weeks while it’s curing to ensure it cures evenly. 

All this, not to mention precautions taken to avoid white soda ash developing on top, ricing, or dreaded orange spots. 

Where I live here in Hawaii, we have a lot of humidity and my cold process soaps tended to sweat even after a long curing process, meaning they’d gather condensation and be a wet mess.  So all in all, with cold process, a couple of months after you began, your soap is finally ready for use.  

Don’t get me wrong, I liked the whole saga of cold process… for a while.  I enjoyed taking time in each step and the beautiful swirls you can make.  But when I started having more orders and going to the farmer’s market with my soaps, it became harder to predict what I should make. And people don’t really love it if you say, “thank you! your order will be ready in 2 months.  I have to go start a batch of cold process soap now!”

Now flip to hot process… the oils heat up in the crock pot and you make the lye solution while you wait.  When the oils are all melted you can add the lye to the crock pot and mix them together.  You wait for the vaseline stage (which is sort of similar to the cold process get phase- more details are coming on all of this), then it’s done cooking!  When it’s cooled down a bit, you can add colorants and scents, mold it and set it somewhere to solidify.  Later that day or the next morning, you can unmold it, cut it, and USE it!  A couple of days to harden sometimes helps, but it’s safe to use that same day!

You don’t have to wait 4-6 weeks and in my opinion, there’s much less room for tragic mistakes and unlucky disasters with hot process.  And hot process is less demanding and particular.  Hot process is how pioneers made soap over the fire!  It’s an oldie and a goodie!  And you can have handmade soap you made by the sink as soon as tomorrow!