Glycerine Rivers: Secret Revealed

Glycerine Rivers: Secret Revealed

posted in: Auntie Clara's Blog, Blog Post | 69

Most seasoned soapmakers are well familiar with the phenomenon commonly known as glycerine rivers, TD (titanium dioxide) rivers, TD crackle or glycerine separation. The terms are all descriptive of what the phenomenon looks like: translucent rivers or streaks in a body of opaque soap. I’m not a chemist so I won’t attempt to give any conclusive explanation of the chemistry that goes into the formation of glycerine rivers, but when soap goes through gel phase, particles of colour pigment added to the soap seem to gravitate and stick to the greasy, water-repellent tails of the soap molecules while leaving the water-soluble heads of the molecules without pigment. This happens sometimes when soap coloured with titanium dioxide and other colour pigments goes through gel phase – but not always.

Glycerin Rivers In Cured Soap
Glycerine rivers in cured soap. Though glycerine rivers often occur in soap with titanium dioxide (the white top part), they can also occur with other pigments such as the yellow iron oxide in the lower part.

Soap with glycerine rivers is not technically inferior to other soap. However, the translucent ‘rivers’ are more water-heavy and will shrink more than other parts of the soap as water evaporates during cure. This can be seen as a slight indentation of the translucent areas. Some soapmakers like the look and ’embrace the rivers’, others think the rivers are ugly and some, like me, would just like to be able to understand the glycerine rivers so that we can make them happen or not make them happen as we please.

Over the years I’ve tried to read up on the reasons for glycerine rivers and I’ve asked more experienced soapmakers about it, but the only decisive answer I got was “it’s because of heat” and “don’t gel if you don’t want rivers”. Well, I wasn’t satisfied with that because I let almost all my soaps go through gel phase and sometimes when using colour pigments I would have rivers – but sometimes not. So yes, colour pigment and heat are prerequisites for glycerine rivers, but I felt there had to be more to the true answer.

Glycerin rivers in blue ultramarine and titanium dioxide
Glycerine rivers in a blend of blue ultramarine and titanium dioxide. No rivers in the parts without added colour pigment.

Going over my own soaping history I often had glycerine rivers when I first started soaping. That frequency has decreased and I rarely have them at all these days. Interestingly other soapers have said the same thing. So what have I changed? Yes, I have tweaked recipes and I like to go with lighter trace than I did in the beginning, but the one big difference is water discount. In the beginning I would always use a lye/water ratio of at least 1/2.3. Now I regularly use a lye/water ratio of 1/1.4. So, my feeling was that it was water-related. I’ve been talking about this, but yesterday I decided to finally put my hypothesis to the test – properly.

To test the significance of water-content on the formation of glycerine rivers I had to rule out as many other variables as possible. I felt the best way to do this was to test it in one single batch. That way I could make sure that the oils, colour, fragrance and temps including ambient temp and meteorological circumstances were all exactly the same.

To keep my experiment as simple as possible I chose a very basic formula for my test soap: 20% coconut oil, 40% palm oil and 40% olive oil with a 5% superfat. Since I wanted to avoid anything that would cause acceleration of saponification I chose straight lemongrass eo for fragrance (I also anticipated ugly soap for home use and hubby likes lemongrass  ). For colour pigment I used 1 tsp of titanium dioxide mixed with a small amount of glycerin for my batch of 1000g of oils.

I added the colourant and fragrance to the oils and stickblended carefully before adding the 1/1.4 lye/water solution which was warm but not hot. I stickblended the batter to very light trace. I then divided the batter into two identical jugs, weighing them to make sure that I had divided the batch exactly in half. Then, while stirring with a whisk, I added enough warm water to the one half for the lye/water ratio to be 1/2.4 in that half.

I wanted to ensure that both halves got equal heat. Since heat travels upwards I felt that placing one half of the soap on top of the other might jeopardize equality and so, using a lengthwise divider I poured both halves of the batch side by side in the same log mould and placed it in a 60C oven for 4h to ensure that the soap would go through gel phase.

Glycerine River Soap With Inverted Stamp Decor
Freshly poured. Gave the two sides different top treatments – to be able to tell them apart in case they’d look the same inside. The squiggles are on the low-water side, the parallel ridges are on the high-water side.
Glycerin River Soap With Inverted Stamp Decor
Fresh out of the oven, still hot in the mould.
Glycerin River Soap With Inverted Stamp Decor
Just before cutting. What will be revealed?

I cut it this morning and yes, you guessed it, I wouldn’t have been doing all this talking if the results hadn’t been pretty spectacular! The same batch with the same oils, same amount of colourant, same fragrance and same external heat produced plenty of spectacular glycerine rivers on the water-heavy side but no rivers at all on the water-discounted side. The only other variable here except water content is that I hand-mixed the high-water half a little more than the low-water half to incorporate the added water.

Glycerin River Soap
I rarely set out to make ugly soap, but this time I had – and I was richly rewarded. The low-water half (on the right) does not have any sign of glycerine rivers despite the titanium dioxide and the heat whereas the high-water half (on the left) is swimming with rivers.
Glycerin River Soap
The end of the log. The high-water half reached slightly thicker trace than the low-water half, but it was still fluid enough to pour easily into the mould.
Glycerin River Soap
The inside end of the log edited to add contrast showing off a fine crackle of glycerine rivers running throughout the high-water half of the log. It will be interesting to see how the shape of the bars change during cure. Because the left half has a significantly higher water content than the right, I predict that the left half will shrink more than the right. Time will tell.

So, for all of those who say “I’d love to get rivers but I don’t seem to be able” this is pretty good news. Just up the water and your chances will grow. And for those who say “I’m bummed because I want to force gel but my soaps are full of rivers” it’s equally good news: by doing a steep water discount you may be able to avoid them. What this experiment does not tell us is where the line is drawn; at what exact water concentration (heat, pressure, formula, fragrance, colourant etc being equal) do glycerine rivers start showing up? But that’s a different experiment and I will leave it up to somebody else 🙂


69 Responses

  1. Wow, how interesting, this is pretty groundbreaking stuff!! Come to think of it, a lot of the soaps I have made with no water discount (florals typically) have been the ones I get ‘rivers’ in them, well this just proves it, if you want to avoid those rivers, choose a non accelerating fragrance and discount like mad! Thank you soooo much for sharing your experimentations, and your soaps are gorgeous too! 🙂

  2. Yasmine

    Thank you for doing this experiment. It has helped me a great deal.

  3. Marie Descent

    Thank you Clara for such an excellent post on the dreaded glycerin rivers! Your experiment was very well thought out and executed. And for sure, the results are indeed very telling. (You say you’re not a chemist, but you should be!) As with so many other soapmakers, I had also made the connection between heat and the formation of rivers, but never thought about the water component playing such an important part in the process. I will definitely put this new information to good use in my future soaping endeavours.
    Thank you again and best regards.

  4. But??? If you do a heavy water discount won’t the soap be lye heavy???

  5. This is one of the most exciting posts I’ve read since I started making soap and blogging! Thank you for sharing your experiment and discovery. 🙂
    I had glycerine rivers in one of my earliest soaps, but afterwards, I rarely had it. I hardly used TD during my first couple of months, and by the time I started using it, I had already increased my lye concentration to 33% from 28%. Nowadays I use a lye concentration of 37% or a lye/water ratio of 1/1.7. At this ratio, I almost never get glycerin rivers. If I did, it would just be minor streaks. I always gel my soaps as well.

  6. Wow! Thank you for this!

  7. You are a genius! Excellent experiment. Thank you very much. 🙂

  8. Kimberly H

    Wow! I never would of made the connection to water. When I first started soaping I never once encountered rivers and I always soaped at full water. I often look at my older soaps with the colors so perfect and seamless and wonder, “What am I doing now?”. The only thing that is different from then to now, years later, is that I almost always use a water discount. It is now that I get rivers where I never did before. So in my case is backwards to your theory. Hmmm :/

  9. Very beautiful experiment!

  10. Fascinating! I happen to love the crackly, glyerin river look. I have noticed this in plain soap too. You just have to look harder to see in plain soap. Thanks for sharing!

  11. I don’t think water plays as large of a part as most people think. I’ve commonly had rivers in soaps made with a 50% solution. The largest driving factors I’ve observed are heat and poor mixing, which I blogged about on Modern Soapmaking some time ago. Hand stirring extra water versus not hand stirring the other side is a pretty big variable that can greatly contribute to the duration of saponification and uneven speed of the chemical reaction. Interesting experiment, Clara! It would interesting to take this further and eliminate variables like additives, stirring variances, etc.

  12. I find this really interesting. I can honestly say I have never experienced glycerine rivers in any of my soaps and that means in 20 years of soap making and an enormous variation in soap base oils. When I began making soap I used 30% water but then changed to 33%. The evidence you demonstrate is pretty conclusive but really odd that I have had such a different experience using a much higher ratio of water.

  13. Denise Snow

    Wow! Thank you for sharing this.

  14. Well done, informative and well documented. Thank you for sharing your time and knowledge. I have a few scents I enjoy but get the dreaded glycerin rivers. Have never tried discounting the water, but I will now. Love your deco swirl tops.

  15. Great experiment….I also noticed that I haven’t gotten them in years and that is when I started drastically reducing my water. I knew it couldn’t be the heat alone because I always go through full gel. Thank you so much for sharing your knowledge with everyone!

  16. Your experiment is so clear! And what a surprise that lye concentration can make such a big difference in the outcome of the soap. Thank you so much for sharing your results. You’ve really shed light on what was a soap mystery.

  17. This is BRILLIANT. Love the experimental design, with all the controls. Love the results. And really love the design on top of the soap, which I’ve never seen before. Can I be you when I grow up, LOL. Thanks so much for figuring this out. Your fellow soapers thank you!

  18. Thanks for sharing it, Clara!So useful!

  19. Thanks for all the valuable feedback! I’m happy if my experiment gives others food for thought and perhaps inspiration for more experiments around the rivers. My experiment was very basic and I only tested for water, ie there may be lots of other contributing factors that can be tested such as eg type & amount of pigment used, type & amount of fragrance used and fatty acid profile of the formula. More than one person has questioned my method of gradually mixing in the additional water by hand, and while the old mayonnaise chef in me is pretty confident that my emulsion was very stable (and my colourant, of course, was already carefully mixed into the oils), it’s a valid concern and so my follow-up experiment is in the oven as we speak. One thing I would like to point out is that in my experiment I kept heat constant at 60C. If you increase the heat enough you may well get rivers or streaks in low-water soap as well.

    • Desert Rose Handmade Soaps

      Thanks for sharing, Clara. Do you think this woul apply to milk soaps?(replacing water with milk and/or half milk/half water).thanks

      • At 60C liquid concentration seems to be a significant factor. What you need to take into consideration is that milk contains sugar and sugar will affect the heat generated in the soap. What the practical implications of that are I don’t know; you’ll need to test it. Chances are though, that you’re more likely to see rivers in milk soaps with full liquid than in milk soaps with a big liquid discount – at an ambient temp of 60c.

  20. This is BRILLIANT! Great work and thanks so much for sharing! I’ve been battling glycerin rivers through my last few batches and can’t wait to whip up another batch with a water discount! THANK YOU!

  21. Claudia Wilson

    Absolutely fascinating! Thank you so much for the info.

    It’s also interesting that the higher water volume soap traced slightly thicker than the lower volume water soap.

  22. Concepcion

    Very nice experiment, when you talk about the ratios, you make them in ounces or grams? example lye/water 1/2.4 that means that is 1 part lye and 2.4 parts of water? the .4 is what confuse me, unless you mean 1 oz/gms by 2.4 oz/gms?
    Hope you can help me to understand this, I normally use lye/water ratio 1:2 = 1 part lye by 2 parts water.

    Thanks for sharing such a great experiment, by the way love the top of your soap, how did you make the squiggles?

    • The ratios work in any weight unit you choose. A NaOh/H2O ratio of 1/2.4 means just like you say, 1 part NaOH by 2.4 parts H2O. If you are measuring in tons and your NaOH is 3 tons then your H2O would be 3 tons x 2.4 = 7.2 tons. That’s for a REALLY big soap! 🙂
      The squiggles are made in inverted stamp technique. If you scroll through my blog posts you’ll find a tutorial about it.

  23. Eucalypta

    Interesting theory; love the test soap!
    I do’t know if you noticed, but when the glycerine rivers occur with TiO2, the ends of the soap don’t display the crackles.
    This is the part where the soap doesn’t gel! So heath certainly is a factor.
    Accellerating FO’s tend to create glycerin rivers in a (plain or coloured) soap as well – even sometimes “geodes”. In this case less water makes the problem worse, so I fear that water reduction on its own is not the solution to avoid crackles.
    IME this fenomenon occurs quite randomly. When I use oil soluble TiO2 I never experienced this problem.
    (I would use a bit of water i.s.o. glycerin to mix the regular TiO2).

    • I’ve definitely noticed that the surface of the soap (both top, sides, bottom and ends) rarely show rivers even if the interior has lots of them. Not so sure though that that’s because these areas don’t gel. If you make an identical soap using identical method but with colour pigment instead of TD you’ll see that you have uniform deep, gelled colour all the way to the edges. Likewise, when you force gel in a relatively hot oven the soap often gels from the outside in as well as from the inside out, ie it definitely gels all the way out, yet you are more likely to see streaks inside the soap than on the surfaces. I think the lack of surface rivers has got to do with temperature differentials but not necessarily with incomplete gel.
      When an fo ‘accelerates’ it increases the rate of saponification and therefore the generation of heat. If it happens in a high-water soap the soap will rapidly hit gel phase and if unlucky, overshoot typical high-water gel temp and overheat (perhaps with ‘stalagmites’ as a result). The likelyhood that a low-water soap will overshoot its typical gel temp is smaller since that temp will be higher.
      I don’t think there’s much randomeness here 🙂 : it depends on temp and what exact temp that is will depend on the water concentration. How quickly the soap reaches that temp, how much it overshoots that temp or how long it stays at that temp depends on variables like mixing temps, fragrances, oils used, ambient heat, agitation etc. But if you regularly bring high-water soap with TD to full gel without ever experiencing rivers, that’s very interesting. Of course, if you add water to your colourants without discounting that water from your lye solution you increase the water content of the soap, ie you bring down the temp at which the soap will reach gel phase.

  24. What a great experiment! Thank you for all those comments, both yours and your visitors. I am learning a lot! It happened only once to me, The soap turned out even more beautiful I think. I was wandering how I could do it again! Thanks!!!

  25. Fiona Greiffenberg

    Hi Clara, Do you use an anatase or rutile grade TiO2? Best Regards,

    • Sorry Fiona, I don’t know in what kind of crystal form this titanium dioxide occurred in nature or how it was treated later on. I’m based in South Africa and soap making supplies here rarely come with that kind of information.. All I can tell you is that the titanium dioxide I use is readily dispersable in both water and oil. It’s suggested that rutile might be safer but since soap is not a leave on product I’m not overly concerned with the possibility of it being anatase. My personal preference is to formulate soap with oils light in colour rather than using titanium dioxide..

  26. Sherri Blair

    Can you clarify the benefits of gelling vs. non-gelling with regards to the quality/appearance/coloring of the final product?

    • Gelled soap is typically more translucent than un-gelled soap. Un-gelled soap has a creamier look but colours tend to be deeper and more intense in gelled soap. After a full cure un-gelled and gelled soap may feel equally hard to the touch when dry but in use un-gelled soap absorbs water more readily than gelled soap, ie un-gelled soap becomes ‘mushy’ faster when placed in water and dissolves more readily. Everything else equal you could say that gelled soap lasts longer in use.

  27. […] interest in heat and gelling related issues of late (you can read about my previous experiments here and here) I tend to home in on images related to that. A couple of months ago I saw a striking […]

  28. I had just discovered this. Since using my pigments dispersable in water, I’ve had a heap of glycerin rivers!

    • By adding water to disperse your pigments you add to the total water content of the soap bringing down the temp at which the soap goeas through gel phase. That in itself could be adding to the formation of rivers. Also, some pigments may well be more prone to separation than others.

  29. […] blog posts: Auntie Clara’s first experiment and Auntie Clara’s follow-up […]

  30. Kevin Dunn

    Hi Clara,

    I was asked about glycerine rivers recently, and a little googling pulled up your blog. I’m not sure I can do much better than you have. I had suspected (a) partial get (b) something added at trace. Your experiment is quite wonderful. As a further experiment, I would suggest repeating it, but this time separate the oils into two batches before adding the lye. To one batch add your 1/2.4 lye and to the other add your 1/1.4 lye. This would answer the question as to whether the “rivers” develop during saponification or whether they are simply rivers of high-water soap. I have a few other experiments to suggest if you have the time and inclination. I do a regular bi-monthly column for the Saponifier Magazine. Would you be interested in my showcasing your experiments in one of my columns? Congratulations! You are a natural born scientist.

    • Hi Kevin! I feel tempted to say that great minds think alike, but that would seem a tad presumptuous 🙂 A week after conducting this experiment I repeated it and did just what you suggest: I combined oils and added everything except lye solution. I divided this mixture in two equal parts and added high water lye solution to the one part and low water lye solution to the other part. Then continued just like I did in this first experiment – with pretty much identical results. I described the second experiment in this blog post:

      What remains a mystery to me – and to many others – is the exact why and how of the movement and ‘separation’ of the pigment in the soap, and the interesting transparent look and chemical composition of the ‘rivers’. They are commonly known as ‘glycerine rivers’, but I doubt that they are higher in glycerine than the surrounding, opaque areas. They don’t wear down faster in use and they don’t attract moisture more than the surrounding soap. They do, however, pull back on themselves when the fresh soap is cut, creating indentations in the cut surface of the soap. This seems to be be an indication that the transparent areas, whatever their chemical composition, expand more than the surrounding soap while the soap is hot and then become low-pressure areas as the soap cools down. I have some pictures illustrating this in this blog post:

      Anyway, I’d love to discuss experiments and I’d be very honoured to have my work featured in one of your columns.

  31. Kevin Dunn

    We have investigated low and high water soaps.. There is a chapter in Scientific Soapmaking. The water content makes a huge effect on the temperature at which a soap gels. If the water is low enough, the temperature will never get hot enough to gel.. I suspect your low-water soap never gelled and your high-water soap did. That’s not an explanation in and of itself, but it would be good to know whether you observed that. I have heard it said that titanium dioxide (or some pigment) is needed to see the rivers. It would be good to document this as carefully as you have done. That is, repeat your experiment exactly, but without any pigment. That would establish the importance of pigment, rather than just a partial gel. The next experiment I would run after that would be to repeat your experiment in a transparent (but insulated) container and do time-lapse photography on it. Gel phase often starts in a few spots that then get larger and larger. Does the gel exclude TiO2, or is TiO2 drawn into it? I would then repeat the experiment using water concentrations intermediate between your low and high-water soaps. Is there a threshold water content? My students this semester are already working on other projects. If you have time to do some more experiments, I would love to consult with you. Otherwise, it will be the fall before I have time to devote to it. You have really done some fine work here.

    • Thanks! With reference to Scientific Soapmaking I did devote quite a bit of discussion to whether the soap gelled or didn’t in the follow-up experiment . Transition to gel phase is definitely required for rivers to occur, but since I don’t know what the rivers are I don’t know whether the relatively quick rise in temp and gradual transition between phases of low-water soap creates less favourable circumstances for rivers to occur than the slow rise and fall in temp but quick phase transition of high-water soap. If you push up the temp enough on a low-water soap you will get rivers there as well, but by keeping the water low, mould size small, and temp relatively low you can get away with oven processing low-water soap for faster saponification and shorter production time – without getting rivers. This is a fairly important practical aspect from the soapmaker’s point of view.

      In my experience, pigment makes the ‘rivers’ visible by creating a contrast in colour or shade, but invariably the rivers will also be visible as indentations in the cut surface. TiO2 shows off rivers particularly well, but you get the same effect with a range of pigments including ultramarines, oxides, charcoal and beer. What I think is of particular interest is that rivers tend to show up on the border between areas with different water concentrations. In practice this may happen where colourant or clay dispersed in water has been added to one part of the soap but not to another. The difference in water concentration will cause differences in temperature and phase development during saponification and between the two areas a transparent, dark line will form. This is clearly visible in some of the pictures in the blog post
      An interesting practical update on the glycerine river experiment is that the line on the border between the high-water and low-water soap was the area to wear down the fastest when the soap bars were used. This happened on all the bars from the first as well as from the second experiment.

      Next, I’ll go and hunt for a transparent soap mould 🙂

  32. Oh, wow! What a simple solution to such a frustrating problem! TD crackle has been an on going issue in my soap bubble and I’ve been driving myself crazy trying to figure out how to make it stop! I can’t wait to test this idea. Thank you so, so much!!

    • It’s worth trying a sizeable water discount. With less water the soap needs a higher temp to reach full gel phase which is when the rivers happen. Many who have tried have told me that a steep water discount solved the problem for them.

  33. Thank you so much for the experiment! I had quite a few batches with glycerin rivers a recently, I tried different temperatures, switching from TD for oil to TD for water, and many other “fixes.” Your water discount solution is the only one that consistently works for me!

  34. Bonny Soap Scotland

    Thank you very much Clara, you have helped me understand a problem I have had. I started using a wine box mould with a divider. (1500g per side.) Every time I use it I get one log with no rivers and one with. I have been using different oxides and colours in each but the log that I had Lake powder in was always the one with the rivers so I have been blaming this., This morning I unmoulded two logs and noticed a great deal of moisture on the lining paper on the side with the rivers and no moisture on the no river soap. I will try a water discount today and see if I get rid of the rivers as it happens every time I use this mould. Many thanks Yvonne.

    • Water content could be the culprit, but uneven heat distribution could be another if you say that two logs in the same mould behave differently. Is there a pattern in the progression of how you fill the mould? Is it the side that you fill second that gets the rivers? Or do you keep the mould in a place where it’s warmer on the one side than the other?

      • Bonny Soap Scotland

        Hi Clara, Thank you for your reply. Yes there is a pattern to my filling the moulds. It seems to be the first soap in the mould that gets the rivers but I have noticed I tend to sit my soaps near the old range we have. I am probably not turning them evenly. I tried a water discount., it did improved the rivers by a great deal. I only could see a few of them in the very centre of the first soap in the mould where I guess it is the warmest. I live on a very small Scottish Island so have got used to sitting the soap near the range over the winter when it is freezing but they were single moulds and were fine, may be time to go back to the single moulds and follow your advice about heat distribution. 🙂 . Your advice has helped a great deal. Many thanks I have learned a great deal from your website. Yvonne.

        • Thanks! I hope you find the solution. Making small adjustments and watching the outcome carefully each time is probably the way to go.

  35. […] Soap Labels Large Collection of Cold Process Soap Recipes How to Add Milk to Lye for CP Milk Soaps Understanding Glycerin Rivers in CP Soap Understanding Gel Phase Calculating the Amount of Soap to Fill a Soap Mold Soapmaking Oils Chart […]

  36. I personally love the “antique” feel that glycerine rivers give certain soaps! Nice to know that a water discount can help ward them off when they aren’t wanted though. I think your half and half soap is lovely, not ugly at all. It has a nice weathered look to it which is the rage in interior decor these days!

    • I also think glycerine rivers can look cool – sometimes more so than others. Being able to make them happen at will – or avoiding them if that’s what the design calls for – is also pretty cool.

  37. Dragonfly

    Thank you, thank you, thank you!! I was beating my head trying to figure out why all of a sudden my soaps, which I wanted creamy suddenly started having glycerin rivers. I have been using more water. I had kind of suspected this might be the case but didn’t have the experiment to prove it. I also feel better that some seem to like the look of rivers as maybe all is not lost for all my loaves with rivers. I love the one opinion that it looks “antique”. Great to know now if I don’t want it them (or do) what I can do about it. Be in control so to speak. Well as much as one can be in the soap world. LOL 🙂

    • I think there is a whole design chapter waiting to be unveiled in the glycerine rivers. To be able to not just get them but make them at will either wide and deep or the finest crackle, straight or curved etc, that would be very cool. When we stop talking about how to get them and start talking about what to do with them now that we have them we will have taken a step in the right direction. Rehabilitating the glycerine rivers, as it were 🙂

  38. You by far are one of my favorite soaping gurus. I aspire to be as knowledgeable as you someday. Wonderful results!!!

  39. […] experiments on creating glycerine rivers had me captivated and led me to try creating these amazing […]

  40. Thanks for the great information! It seems like my trace speeds up with a big h2o discount and makes it difficult to swirl. …might be my recipe? Any suggestions would be greatly appreciated.

    • Together with a row of other things water content influences the rate of saponification, i.e. the speed at which the oils and lye in the batter turn into soap and glycerine. Everything else equal a stronger lye solution will cause quicker saponification. This means that you have to carefully manage other factors that accelerate saponification such as mixing temperature and agitation (stickblending) as well as additives that may speed things up. When soaping without extra water you need to keep temps low, be careful not to overblend and don’t use essential oils and fragrance oils that speed up trace.

  41. Clara,

    Thank you so much for your experiment. I saw some pictures on glycerine rivers and found them beautiful so I wanted to attempt them for my “Frost” soap to make it look like ice. I made a batch of soap, colored with charcoal to achieve a medium blue/gray. Temp of lye was about 125 F (with water : lye ratio 2.7 : 1) and oils about 115 F. Let it come to a thick trace, poured in three molds that I then put in a preheated oven (200F) for about 15 min before turning it off with the oven light on and kept it there for 4-5 more hours. Then put took them out and left them wrapped in towels over night. When I cut them I got only a few single rivers towards the top of the loafs just in a few spot. Say about 6 bars out of 30. Any suggestions in what to change to get a higher probability in getting them? Recipe: ca 27% Coconut, 27% Olive Oil, 27% Palm, 9.5 Avocado Oil, 9.5 Apricot Kernel Oil

    • Hi Cecilia. It’s possible that the amount of pigment wasn’t enough to really show off the rivers. On the other hand it’s also possible that the thickness of trace had something to do with it. When I’ve made rivers on purpose I’ve kept the high-water soap at 60C for several hours. High-water soap will go through full gel phase right around 60C so by keeping the soap at that temp I prolong gel phase. In this recent article by Kevin Dunn he mentions prolonged gel phase as a contributing factor. So, instead of putting the soap in a hot oven and turning it off it’s probably more effective to keep the temp around 130F-140F for 2-3h.

  42. Hi Clara,
    Thank you for your article, this is a very interesting experiment. I am now having a great deal of trouble with major rivers appearing in my soaps that contain titanium dioxide resulting in many logs of spoilt soap that I will not be able to sell. I am using the same recipes, ingredients and techniques that I have always used, the only variant that I have is the room air temperature as I have recently moved to a colder climate.
    I always gell my soaps, using timber log moulds which I cover with a blanket in winter and a towel in summer.
    The air temperature at my previous home was between 14C to 26C. My soap would usually fully gell within 2 hours of being poured and I would keep the soap covered for the full 24 hours. I did not remove the blanket even after gell stage was reached. I found that if I did not cover the soap I would get a partial gell and sometimes unsightly white patches around the edges if the soap got too cold. The only time that I got the glycerine rivers was one very hot summer when the temperatures were around 35C and I used oil dispersible Titanium Dioxide. I switched to water dispersible titanium dioxide and on very hot days I did not cover the soap and I had no problems.
    At my current residence the air temperature ranges from 0C to 14C. I have a heater on whilst I am making soap so the air temperature is around 18-20C but the heater is turned off overnight. I insulate the soap, covering with a box and a blanket but I rarely see visible signs of the soap gelling. I can have 2 batches of soap side by side and 1 will split and 1 wont. It is driving me crazy – so much wasted time and costly ingredients. I was wondering if the rate at which the soap heated up and cooled down impacted the outcome? In my situation a prolonged gell phase does not result in more rivers. My current lye/water ratio is 1:2.5, so it is on the high side so I will reduce the water content of my recipe as you suggest and hopefully it will resolve my problems.

    • In a fairly recent article ( Kevin Dunn found that both level of temperature and time exposed to that temperature influenced the formation of glycerine rivers. It’s not impossible that extra insulation (because of low room temp) raises the internal temp in the soap more than light insulation or no insulation on a warm day. The water content as well as any accelerating additives are likely to play a part in this. Also, the size and shape of the mould will have an impact on how the heat generated by saponification is retained or emitted. Keeping mixing temps low and cutting down drastically on water would be my first advice. Next up: use smaller moulds.

  43. Clara,
    Of course, let me just say you are the master. . .quite gifted indeed and thank you so much for sharing your art/knowledge with us. On that note, why not just use the standard 1.5 times the amount of water as lye as a standard (unless you want rivers)? I’m not sure I can think of other ways a high-water discount would be helpful.

    • Wish it were that simple 🙂 If you never make anything but unscented, uncoloured soap there is little reason, as you say, to use any more than minimum water. However, many scents and some colourants and other additives accelerate trace to such an extent that you won’t be able to make intricate designs with relatively fast-moving low-water soap. A higher water concentration slows down saponification significantly and gives more time for decorative work. Also, if full gel phase is something you are looking for (eg because you want a certain texture or intensity of colour) you’ll struggle to get that with low-water soap if your moulds are relatively small and you don’t have the option to add extra heat e.g. in an oven.

  44. Thank you, thank you…. since I almost always CPOP my soap I had actually given up on using Tit. Dioxide to prevent glycerin rivers or crackles. Your carefully prepared experiment is so very valuable – and has rekindled my interest in new fancy colored patterns.

    • You just need to be aware that the cpop I do here is different to what most soapers do. You specifically don’t want the soap to enter full gel phase so you need to keep mixing temps low and oven temp no higher than 60C max.

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