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From the PBSW Archives: So, What’s This Hot Process Thing?

Posted by Hayley on

Originally published February 1, 2012:

As many of you know, I’ve been working on my hot process soap formula for the past few months. It’s finally ready to see the light of day, & I couldn’t be more excited. I’ve been asked a lot of questions during development, so here’s a quick Q&A to slightly demystify the world of Real Soap…

Wait, “Real Soap”? What were you selling before?

Alright, yes, my luxury bars that you know & love are, in fact, Real Soap. They are glycerin soaps, or melt-&-pour, as some of you may know it. I get my glycerin base in huge 50-pound blocks from a wonderful manufacturer in California. They use real oils & no propylene glycol or artificial foaming agents, unlike the stuff you find at the grocery & craft stores. Technically, glycerin base is already soap, ready to use – it’s just not very pretty, or smooth, or nicely scented. To make my luxury bars, I chop the base, melt it down, scent & color it & cast it in molds. Not rocket science, no, but I have a good time & get to focus most of my energy on making amazing scent blends.

Making soap from scratch, on the other hand, is a journey in applied chemistry, taking oils & butters & caustic soda & water & making magic. It requires very close attention to detail, an exceptionally accurate scale, & protective eye wear. It’s not the kind of project one launches into all willynilly, as sloppy technique or a bad recipe can result in soap that leaves the skin dry, irritated or, worst-case scenario, with chemical burns. So. Soap from scratch – not for amateurs.

But. Well made, thoughtfully-formulated soap from scratch can be a beautiful thing, silky & moisturizing & tailored specifically to the maker’s needs. That last bit is what drew me into wanting to develop my own soap formula.

Hot-press? What’s that?

Not hot press, hot process. There are two main ways to make soap from scratch. The most common method is cold process, where the oils & butters & lye are combined at a fairly low temperature (around 100 degrees Fahrenheit), & the necessary chemical reaction is allowed to take place over a 4-6 week curing period before the soap is able to be safely used. The end texture can be smooth & hard as marble, with delicious peaks & swirls & all kinds of awesomeness. My friend Britton makes some of the best cold process soap around.

The less common method is hot process, which uses heat to speed up & complete the chemical reaction between the lye & oils, allowing the soap to be used immediately. Hot process soaps tend to look more rustic, slightly shaggy & marbleized compared to their cold process cousins. What they lack in sophistication, though, they more than make up for when it comes to scent retention & clarity. Cold process soap requires the scent to be added to the batter while the lye is still active, which can distort or even eat the scent entirely – and you never know quite what’s going to happen until the soap is fully cured. Hot process soap, on the other hand, is fully cooked before the scent is added, meaning that it stays much truer to the original fragrance – a very important advantage to scent hounds like myself.

So wait, you cook soap?

Yeppers. In a slow-cooker, no less. Here’s what it looks like while it’s working!

When the soap batter has fully cooked, I stir in the fragrance & colorants & glop it into the mold. Once cooled overnight, I can cut it into bars. I’m letting my bars dry on the rack for a few weeks before wrapping & selling them – this helps evaporate some more of the water weight & makes for a harder, longer-lasting bar of soap.

I’ll do a post in the upcoming weeks on the full technique, but I hope this proves a quick & easy introduction to hot process soap & why I’m so excited. Look for additional scents in the upcoming weeks, including an essential-oils-and-beer bar & a sticky patchouli-tea-and-chocolate blend that’s downright edible…