Tests of LS made with Glycerin-Water vs Water-only lye solutions

When making the KOH solution for liquid soap (LS), you can dilute the KOH in all water, all glycerin, or a mixture of the two. Each method of making the lye solutions has its pros and cons:

All water:
cheapest because you don't have to buy the glycerin,
KOH dissolves fast in water,
soap batter takes longer to come to trace,
1/9/2015 update -- may want to use a hot process method to speed up saponification, but can be done cold-process
soap takes a longer time to fully saponify

All glycerin:
more expensive due to the amount of glycerin needed
have to heat the glycerin-KOH mixture to make the lye solution,
KOH takes a long time (maybe 10 minutes) to fully dissolve,
1/9/2015 update -- trace happens very fast, so you can easily use a cold process method to saponify,
soap takes a very short time to fully saponify

Water-glycerin mix:
medium cost because you use only some glycerin,
if you mix the KOH in just water, the KOH dissolves fast,
trace happens fast,
1/9/2015 update -- trace happens very fast, so you can easily use a cold process method to saponify,
soap takes a short time to fully saponify

So far, I've used two different water-glycerin mixtures as well as water only to make my LS. I have not used glycerin only, because I like the ease and safety of dissolving the KOH in room temperature water -- I'm not too keen on the idea of heating the lye solution for 10 minutes or so to get the KOH to dissolve.

1/9/2015 update -- If you do choose to use glycerin only method, mix the KOH and the glycerin at room temperature, and then heat up the mixture. This is safer than adding KOH to hot glycerin and works just as well. (Thanks, Irish Lass, for this tip!)

There are other issues to consider about these three variations that I hadn't quite realized when studying up about the different ways to make LS. For example, a person on a Facebook liquid soaping group complained about her liquid soap thickening after she added lavender EO. She felt the problem was caused by the glycerin method she had used to make the soap -- she thought the added glycerin was causing the problem, so she said was going back to making LS with only water, since she didn't have problems with lavender EO with the water-only LS.

I had seen a similar problem when using some EOs to scent diluted liquid soap, so I got curious about whether it was the added glycerin that was causing this thickening. So here's an outline of the experiments I've been doing lately:

***

Test 1 -- Will EOs thicken a glycerin-water LS?

I already had a LS paste (Batch II) on hand that I had made in September. I had used the IrishLass/3BeesCarrie recipe of 10% castor, 25% coconut oil, and 65% olive. The lye is 100% KOH and the lye solution concentration was 25% (3 parts water to 1 part lye). I used 3% superfat and set my KOH purity at 96% per info from my supplier.

I dissolved the KOH in an equal weight of water, and then I mixed in glycerin at 2 times the weight of KOH. So, for example, if I needed 75 g KOH for my batch, I dissolved that in 1 X 75 = 75 g water, and I added 2 X 75 = 150 g of glycerin.

I diluted the finished paste in a ratio of 1 part paste to 0.75 parts water plus 3% sodium lactate solution, again per Irish Lass' instructions. When diluted this way, this LS has a smooth, syrupy consistency similar to Dawn hand dishwashing detergent.

I measured out 10 g of diluted LS into each of 4 little bowls. I added two drops of just one EO -- peppermint, lavender, fir needle, and a citrus blend. The citrus blend and the fir needle EOs did not change the viscosity or texture of the LS. The lavender thickened its sample of LS, but the texture remained smooth. The peppermint thickened the LS to an unattractive clumpy peanut butter texture -- the LS became stiff enough that a toothpick would stand upright in it.

Conclusion -- Yes, some EOs will thicken this diluted LS.

***

To be continued....

Test 2 -- What is the difference between LS made with more glycerin, less glycerin, and no glycerin?

The next test took a little more doing. Remember I already had a LS made with 1 part water and 2 parts glycerin. That is Batch II -- my "more glycerin" batch.

I made two more batches of the same recipe, changing only the way I made the lye solution. Batch III, was made with a KOH solution made with 2 parts water and 1 part glycerin. This is my "less glycerin" batch. Batch IV was made with a KOH-water solution -- my "no glycerin" batch.

The paste from these three batches looks and feels quite different. The paste from Batch II is a firm, beautifully translucent, golden gel that is shiny and just slightly sticky. I cold processed this batch. It hit a maximum temperature of 185 degrees F, and it reached a thick taffy stage in under 15 minutes. After cooling a bit to a sensible temperature, it was zap free when I tested it about 2 hours later. This was a fun batch of soap to make!

Batch III is a slightly softer, golden tan, partly translucent paste with a slightly shiny luster. It's firmer and a bit less sticky than peanut butter. I cold processed this batch as well. Batch III reached a maximum temperature of 150 degrees F and took just under 20 minutes to hit a thick taffy stage -- so a little cooler and a little longer than Batch II. It was zap free shortly after hitting the taffy stage. I don't think it got as hot as Batch II and it took longer, because Batch III was only 1/3 the size of the other batch (500 g of oils).

Batch IV was the same size as Batch II. This soap is a soft, very sticky paste. It is also golden tan, but fully opaque with a dull luster. It took about 50 minutes to saponify to a thick taffy texture, but I decided to microwave it several times to warm up the batter and keep the saponification moving along -- basically an impromptu hot process method. Batches II and III lost less than 4% of their weight during saponification, but Batch IV lost about 15% of its weight because of the extra time and extra heating it required.

All three batches diluted to a clear solution. Batch II with the most glycerin is a bright clear yellow. The other two are a darker golden yellow with a slight brownish cast. Since the pastes for Batches III and IV are also darker than II, I'm not surprised there is a color difference in the diluted LS. I have to say the true test of the color would be if I had made all three batches the same size and all on the same day. There might be some differences due to Batch II being older and larger.

The lather for the three diluted LS is similar. If I had to pick small nits, I'd say Batch II with the most glycerin has slightly less lather, but the difference is small enough it would not be noticed by the average soap user. Again, this slight difference may be due to Batch II not being made along with the other two.

I did a test with Batch II some weeks ago by diluting the paste (1) with all water and (2) with a mixture of glycerin and water. The discussion is in this thread: http://www.soapmakingforum.com/showpost.php?p=450728&postcount=85 and also see post 76. I did see a difference in the lather in this test -- there was less lather when I diluted with a glycerin-water mixture. I also saw a viscosity difference -- the glycerin-water dilution was more watery. After the two dilutions sat for several weeks, this viscosity difference was still obvious.

Conclusion: The way the KOH solution is made does affect the color and texture of the paste and the time and any extra heat needed to saponify the batch. A cold process method will work if you use some glycerin to make the KOH solution. ** edit: A hot process method may be more convenient if you only use water to make the KOH solution, but according to other LS makers, a CP method will still work with a water-only LS recipe. ** I'm not sure the way the KOH solution is made has a big effect on the color and lather of the diluted soap -- there may be slight differences.

Photos:
First 2 photos each show, from left to right: Batch II (more glycerin), Batch III (less glycerin), and Batch IV (no glycerin).
Photo 3: Batch II lather
Photo 4: Batch III lather
Photo 5: Batch IV lather

***

to be continued...

Test 3 -- Do EOs thicken LS made with glycerin and do EOs not thicken LS made with only water?

So now I repeated my first test with the EOs, but now I used my three different diluted LS. I only used lavender EO and peppermint EO this time, since the citrus blend and the fir needle EO didn't have any obvious effect in Test 1.

I measured 10 g of each diluted LS into a small bowl and added 1 drop of lavender EO to each bowl. I stirred with a toothpick and waited. I added a total of 3 drops of EO in each bowl. I realize that is EO overkill, but in this small of a batch, the differences didn't jump out at me until I had added this much EO.

Lavender EO thickened all of the LS, but Batch II (more glycerin) and Batch III (less glycerin) only thickened a slight amount. Batch IV (no glycerin) became quite a bit more viscous (syrupy). When I poured a dollop of each LS onto waxed paper, the thickened Batch IV soap stood up thicker on the paper. The other two LS spread out thinner.

I washed out the bowls and repeated the test, but this time with peppermint EO. I added a total of 3 drops of EO to each bowl, stirred well, and waited. The results were reversed. Peppermint EO caused Batch II (more glycerin) to thicken and even become unpleasantly clumpy. This goopy thickening of Batch II is pretty much a duplicate of what I saw in Test 1 (see Post 1 above). This change was much more pronounced than the thickening caused by the lavender EO. The other two LS (less glycerin and no glycerin) thickened slightly from the peppermint, but remained smooth liquids.

What is interesting to me is the "less glycerin" batch III was the least affected overall by the two EOs tested. I would have thought if one LS made with glycerin would thicken and even get clumpy, then both would do so.

Conclusion: Essential oils can indeed thicken diluted liquid soap, but it is clear that EOs will thicken liquid soap made only with water as well as soap made with a glycerin-water mixture.

Photos:
First 2 photos: Lavender EO test. Left to right: Batch II (more glycerin), Batch III (less glycerin), and Batch IV (no glycerin)
Last 2 photos: Peppermint EO test. Left to right: Batch II (more glycerin), Batch III (less glycerin), and Batch IV (no glycerin).

Awesome explanations, as usual!

Have you ever tried to speed saponification using 0.5 oz grated NaOH soap? Works well for me.

No, Susie, I haven't, but I've read about it. I know you've mentioned it a few times and like how it works for you.

The old soap makers from the 1800s occasionally wrote about recycling a dilute soap solution back into the next batch. Their thinking was the ready-made soap allowed the fats and lye to emulsify and saponify more quickly. And it was also a way to harvest soap that they could not otherwise recapture.

I find that grated NaOH soap gets me to trace faster than KOH paste. I am not at all sure why this is, but the difference is definitely there.

Awesome thread! Thank you so much, DeeAnna, for giving us a peek into your 'lab', so to speak, and taking the time to share your findings with us.


IrishLass

This was fun, although time consuming. I can tell I'm out of practice designing and doing research experiments. I wish I had the resources and time to do more of this kind of thing -- I'm a bit of a Kevin-Dunn-type at heart, sans chemistry lab, funding, and eager grad students.

My day job is extremely busy from September through December and I get really tired and worn out by the end of this annual busy season. We shut the shop down from Christmas through New Years so I get some time to rest and recuperate -- and do some kitchen chemistry like this. I think my dear, sweet husband was happy to see the soapy mess in the kitchen because he knew was getting his usual cheerful and curious wife back, even at the cost of not getting regular meals!

Very useful information and in depth experiment. Thank you for sharing! I am confused though, I have been successful at making multiple batches of cold process soap with a water only/lye mixture. All of which have fully traced and saponified??? I am curious as to why you state you must need heat to reach saponification, or is that just with the current oils you are using? Thanks!

As always with your very informative posts, DeeAnna, WOW! That's a lot of time consuming, but fascinating, kitchen chemistry. I REALLY appreciate the work it took not only to perform the experiments, but to sit and write it all out then include photos. Serious kudos to you!

I had many small, seemingly insignificant, questions running around in my head regarding KOH with water/glycerin/split that you just cleared up for me. I haven't made any LS in about a month because I've been trying to decide what changes I want to make and what the possible outcome would be in lather, ease of dilution and % of dilution, etc. You've just given me a definite direction to take and a well needed kick in the rear to get it done, lol. Thanks SO much! :clap:

Cleangrip -- Susie (a more experienced LS maker on this board) has explained to me that she also does water-only LS with a cold method and has good results. This was my first water-only LS batch, so it's my inexperience showing.

In hindsight, I think my ingredients in the water-only batch were too cold to saponify quickly without adding heat during saponification. So I used the microwave to speed things up, rather than be patient and wait.

I'll tweak my technique next time to see if I can do a CP method with a water-only recipe.

DeeAnna said:

Test 3 -- Do EOs thicken LS made with glycerin and do EOs not thicken LS made with only water?

So now I repeated my first test with the EOs, but now I used my three different diluted LS. I only used lavender EO and peppermint EO this time, since the citrus blend and the fir needle EO didn't have any obvious effect in Test 1.

I measured 10 g of each diluted LS into a small bowl and added 1 drop of lavender EO to each bowl. I stirred with a toothpick and waited. I added a total of 3 drops of EO in each bowl. I realize that is EO overkill, but in this small of a batch, the differences didn't jump out at me until I had added this much EO.

Lavender EO thickened all of the LS, but Batch II (more glycerin) and Batch III (less glycerin) only thickened a slight amount. Batch IV (no glycerin) became quite a bit more viscous (syrupy). When I poured a dollop of each LS onto waxed paper, the thickened Batch IV soap stood up thicker on the paper. The other two LS spread out thinner.

I washed out the bowls and repeated the test, but this time with peppermint EO. I added a total of 3 drops of EO to each bowl, stirred well, and waited. The results were reversed. Peppermint EO caused Batch II (more glycerin) to thicken and even become unpleasantly clumpy. This goopy thickening of Batch II is pretty much a duplicate of what I saw in Test 1 (see Post 1 above). This change was much more pronounced than the thickening caused by the lavender EO. The other two LS (less glycerin and no glycerin) thickened slightly from the peppermint, but remained smooth liquids.

What is interesting to me is the "less glycerin" batch III was the least affected overall by the two EOs tested. I would have thought if one LS made with glycerin would thicken and even get clumpy, then both would do so.

Conclusion: Essential oils can indeed thicken diluted liquid soap, but it is clear that EOs will thicken liquid soap made only with water as well as soap made with a glycerin-water mixture.

Photos:
First 2 photos: Lavender EO test. Left to right: Batch II (more glycerin), Batch III (less glycerin), and Batch IV (no glycerin)
Last 2 photos: Peppermint EO test. Left to right: Batch II (more glycerin), Batch III (less glycerin), and Batch IV (no glycerin).

Click to expand...

I recently made a batch of LS using IrishLass' receipe:
co 35%
oo 10%
castor 30%
shea 5%
cocoa butter 20%
3%sf

IrishLass diluted hers at 1:0.41 water to paste. Mine didn't dilute at that ratio and I ended up using way more water, about 1:1.3. Needless to say, it was runny. When I stumbled across this thread, I was thrilled and thought the eos could salvage my LS.

So I did exactly what DeeAnna did. Put 10g LS each to 2 cups. Added 3 drops of peppermint eo to one cup and 3 drops of lavender eo to the other. To my dismay, they didn't thicken up.

So I thought why DeeAnna could do it and I couldn't. The answer lies in the oils and their fatty acid components.

The fatty acids of my recipe and DeeAnna's (in brackets) are:
Lauric 17 (12)
Myristic 7 (5)
Palmitic 10 (11)
Stearic 10 (3)
Ricinoleic 27 (9)
Oleic 20 (47)
Linoleic 4 (9)
Linolenic 0 (1)

So the main difference is the levels of ricinoleic and oleic acids.

Conclusion: like salt, peppermint and lavender eos can only thicken LS high in olive oil.

After 24 hours of my experiment (see above post), both batches turned jello! I don't know whether it was the eo that did the trick or the water in the soap had all evaporated (as I had just left them uncovered in the room and the daytime temperature was like 90 degrees).

I will make another two batches again tonight, cover them and see how they are on Saturday.

My apologies if someone has already taken note of my conclusion.

If the test batches were small and you left them uncovered, I bet there was enough evaporation to thicken the soap. When I stirred up the small batches of EO and soap shown in the pictures above, the same thing happened to me too. But I think your second experiment is a good idea -- I'm curious to see what happens.

I do know soap can change its thickness over time even if there is no evaporation. The reason why is that soap molecules can take some time -- days or even weeks -- to develop a final structure. They can be found as individual molecules floating around in water or they can organize into small balls or large sheets or sausage shapes. When they change their structure, the viscosity (thickness), opacity, and other qualities of the soap may change as well.

Here is the result of my second experiment.

Both thickened up a tiny bit, noticeable, but the consistency is not as thick as honey. There is no difference between using peppermint eo and lavender eo. My view is it is not worth using eo for thickening LS that is not high in oleic acid because the cost is high and the effect is little, unless you want to scent the LS anyway.

"...I ended up using way more water, about 1:1.3...."

An issue with your experiments that I didn't pick up on earlier is this point. Your soap may have simply been too dilute to respond to the added EOs.

What salt and EOs are doing is shifting the solubility and physical structure of the soap molecules in water. To explain briefly, soap can create different types of pourable but syrupy gels when the water content is in the middle range -- for most soaps, this sweet spot is very, very roughly somewhere between 30% and 70% water with the balance being pure soap.

The gel you get in this sweet spot is created because the soap molecules are banding together to form balls, hotdog shapes, and flat layered sheets. These large structures floating around in the dilution water essentially cause the soap (from our human point of view) to become thick and syrupy. At the low water extreme you'll get non-liquidy paste or solid soap. At the high water extreme, the soap will be a "true" solution that is watery because the soap has fully separated into individual molecules. To thicken a LS with salt or other additive, you really want to start with the LS somewhere inside its sweet spot and thicken from there with additives.

What it sounds to me that you were trying to do is thicken your LS from a watery consistency and all you got was ... a watery consistency. Now that I've picked up on that point, I suspect that might be the main reason why you didn't have very good luck. If your soap is too far out of the "sweet spot" area, you may never get it to thicken with something like EOs or salt -- you'd have to use a separate thickener that thickens a LS independently of the concentration of soap.

That said, it is true that a LS higher in myristic and lauric acids (aka high in coconut oil and similar fats) will have a smaller "sweet spot" than a LS high in oleic acids. So your point in that regard is valid.

In my little experiments, I was using liquid soap diluted at Irish Lass' dilution ratio of 1 part soap paste to 0.75 parts water (compared with your 1 part paste to 1.3 parts water), so my soap was in a much different place in the solubility diagram than your soap was.

DeeAnna, that is a very good point which I missed myself. But I am not sure that my LS was not within the sweet range. It should be because I added water slowly until there was no solid paste. Anyway, a sure way of having thick LS is to keep coconut oil below 10%, which is perfectly fine with hand and body soap. I will have to live with liquidy dish soap.

I don't know why the paste did not dilute at 1:0.41(not 0.75 as the recipe I used is IrishLass' cocoa butter recipe). One probable cause is I used all-water, no glycerine. Has anyone done experiment on this

"...One probable cause is I used all-water, no glycerine. Has anyone done experiment on this..."

Uh, what about the info in my Post #2, above? Is that what you mean?

DeeAnna said:

"...One probable cause is I used all-water, no glycerine. Has anyone done experiment on this..."

Uh, what about the info in my Post #2, above? Is that what you mean?

Click to expand...

I used only water to dissolve the KoH and the paste diluted at 1:1.3. IrishLass used the glycerin method and the paste diluted at 1:0.41. I wonder the amount of dilution water needed will be affected by whether the soap was made with all-water, all-glycerin or part-water-part-glycerin.

I wonder if the glycerin can be subtitute with sugar water? the price will be significantly cheaper.