Soap Challenge: Glycerin Rivers


I wasn't planning to sign-up for the February 2019 Soap Challenge Club - but organizer Amy Warden enlisted the expertise of one of my soap SHEroes, South African soap maker/chemistry geek, Clara Lindberg of Auntie Clara's Handcrafted Cosmetics. (Dammit, Amy!) 

The February Challenge featured "glycerin rivers." Contrary to the name's implication, these aren't liquid rivers - just areas of soap where the pigment has migrated out, leaving clear "rivers" of soap in the bar. To me, the process leaves an odd, visual texture reminiscent of the crackled appearance of an aged oil painting.

Most soap makers' first encounter with glycerin rivers is usually alarming - wondering if something has gone terribly wrong in the production of their soap (yes - this was me years ago). But aside from the unexpected look, assuming your formulation is on point otherwise, there's nothing wrong with a soap containing glycerin rivers.

(Auntie Clara has pursued studying this and other soap chemistry phenomenon, and has written blog posts about how to intentionally create glycerin rivers. A great read, if you're into that sort of thing. I am.)

For the 200+ soap makers participating from dozens of locations around the globe,  Amy offered two versions of the challenge: the regular category features glycerin rivers throughout the bar, the second, more advanced category, requires that some section(s) of the soap contain glycerin rivers, contrasting with other river-free, smooth portions on the same bar.

Why is the second category more advanced? In the regular category, the formulation would be consistent, even if using several colors.  The advanced category requires formulation changes in the same batch (by varying water amounts) to achieve smooth soap in some sections, glycerin rivers in others.

Both versions require CPOP-ing - Cold Processed/Oven Process-ing - the batch after pour, to achieve the heat needed for full gel. "Gel" refers to a version of saponification that produces not only more intense colors and a lovely translucent soap quality, but is also a critical step in producing glycerin rivers. (Note to Clara - I'm pretty sure I had inadvertently achieved them without CPOP-ing in the past).

The other requirement of the challenge (no matter the category) is that designs had to be accomplished in "one pour" - that is, you wouldn't be able to make a plain loaf of soap, allow it to saponify, cut into cubes, then drop into the  glycerin river batch, thus BOOM, providing a contrast of river-ed and non-river-ed design. Nope.

How hard could this be?

Pictured above was my first attempt, in the "regular" category - but some background, first: Here in Colorado, we've had a years-long run of Pine Bark Beetle infestation (climate change suspected), resulting in swaths of dead trees in our forests, including the Western slope of our beloved Rocky Mountain National Park.

As awful as brown trees blanketing random mountain slopes look, the planks cut from the beetle kill are curiously beautiful, with varying degrees of grays and blues throughout. You can see from my concept sketch (based on this online image), the planks look very different from the golden/white hues of typical (healthy) knotty pine. Tree-hugger that I am, I thought it would be interesting to recreate the look, using the natural texture of glycerin rivers in the design. 

And in a nod to my #useitchallenge, I incorporated oils that I don't typically use, but had on hand - grapeseed and rice bran  - along with more typical coconut, sustainable palm & olive oils.

Alas - the rivers only showed up in the white areas. And the soap thickened up so quickly (probably from using copious amounts of Titanium white in the entire batch) that I had to abandon the design before all the raw soap was used. I quickly tossed it into another mold, which came out like this:

Still intriguing looking soap, but again, the glycerin rivers only showed up in the white sections, not the other colors. Why couldn't this go in the advanced category, you ask? Because the formulation was the same throughout - a requisite of the advanced category was that you manipulate the formulation of the same pour in different ways. (Dammit.)

Ironically, the advanced category was sounding easier than the regular one, so my next attempt would purposely produce rivers in some sections, others without, by varying water amounts. I used a base oil combo of olive/coconut/rice bran/tallow/castor, along with titanium white (entire batch), plus Brambleberry's Stormy blue, Queen's purple, and  Moss green micas. The scent was a lavender/spearmint combo - the end result was this:
Thawed Soap

This was more like it: I was going for a smooth white base with smooth green and purple topping (check!). By adding extra water and color to each of the two stormy blue layers, hoped to get a few rivers in the lighter blue and a lot of rivers in the darker blue, then accented with a hanger swirl to bring some of the layers up through each other (visually, like a pond thawing).

Once more, the soap thickened up ultra fast - perhaps from floral essential oil, Titanium white, working at warmer temps, or a combo of these factors - so the hanger swirl was more subtle than if this had been a more fluid soap. As for the rivers? The darker blue section came out great, but the lighter blue seemed to have formed more of a "glycerin creek" - with color migrating out in a band along the white base - rather than a fine layer of rivers throughout. Curious.

As with the first batch, I still really like this soap, but not sure if it fulfilled the requirements of the challenge.

Third time's a charm, right?

I had been tweaking the design and formulation of one of my women's soaps, Incorrigible Flora, for years. Something was not quite right with the background color (Moroccan red clay) in the previous version - the hue didn't allow the stamp detailing to pop. Until this challenge, I hadn't considered how glycerin rivers might provide a striking, yet still neutral background to the stamp. 

I used a palm-free blend of base oils: olive, sweet almond, coconut, castor, babasu, and Shea butter. The scent blend had me a little nervous - geranium rose, spearmint and various citrus - as florals tend to accelerate set-up and, since I was trading out the Moroccan red clay for titanium white, I was already concerned about a speedier rate of trace. 

I did what I could to compensate: heating the essential oils slightly and gently stirring them into the bottom layer of soap (no scent in the top design). I also added an additional 60 g of water and a high amount of titanium white. The soap separated out for the top "bulls-eye" design had a normal amount of water and was further divided out into 3 colors: madder root/raspberry mica, Moroccan red clay, and titanium white. 

As predicted, the main/bottom section of soap thickened quickly, but was still easily poured into a 2-lb mold. As I mixed the top colors, the base soap set up nicely. However, the other colors started setting up quicker than I was accustomed to, despite the fact that I hadn't added any of the EO's nor additional water - I ended up with interesting looking mounds rather than a smoother bulls-eye pattern. 

Figuring out how to cut this loaf was intimidating: 

top of Incorrigible FloraBut - deep breath - cut it I did, and happy to report that the glycerin river'd (main body) /non-glycerin river'd (top) differentiated sections had come out as intended:

And the main section provided a fantastic backdrop to the Milagro Heart stamp:
22019 Incorrigible Flora

So there it is: my Glycerin River journey.

Thanks again to Amy Warden for organizing this intriguing soap challenge and to Clara Lindberg for her continued inspiration. If I hadn't done this challenge I wouldn't have found the missing design piece to this soap.

(...until I once again decide to tinker with it. You never know.)

Soaping pals - did you do this challenge? How did you like your results? Would you do this again or incorporate glycerin rivers into your product line (on purpose)? 

Non-soaping pals: 1) hope that this post wasn't too technical (boring) and 2) what do you think of this effect? 

LMK in the comments below (and thanks for reading this far).

- LMG


8 comments


  • Lisa Melli Gillespie

    Debi – yes – as Coloradans we’re totally bummed about the devastation to our forests, but the resulting wood is super intriguing, which is a bit emotionally conflicting. I hope that you make something really wonderful from your stash, whenever you get to it.
    I’m planning to revisit the beetle-kill design soap without the glycerin river parameters – just thickened up too quickly for what I had hoped to do with the design. But I think the colors worked well and the scent is great, so…another attempt is in the works!


  • Lisa Melli Gillespie

    Helen – Thanks so much for your feedback!


  • Helene Glemet

    Very beautiful design! The crackles from the glycerine rivers really work well!


  • Debi Olsen

    You did such a fabulous job with this, Lisa! I truly love your entry, though I have to admit I’m super drawn to your beetle kill design. Seeing the devastation of our mountains is truly heart breaking but some of the wood salvaged from the pines is breath taking. I have a pile of boards stashed for an amazing “some day” project. Thank you so much for sharing your process and especially, your beautiful soaps!


  • Lisa Melli Gillespie

    Thanks so much, Amy – OK, this challenge WAS actually great fun.
    (I forgive you.) ;)


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