water reduction and cure times

I know cure time helps to somehow make a bar 'better' just by sitting... but in regards to having a 'harder' bar with less loss when using, can a water reduction allow for quicker use and less loss? I'm guessing yes since part of the cure time is to also allow for water loss.

Those who do reductions.. do you still do a 6 week cure on bars that typically only need a 6 week cure with full water? Like.. even though I did a reduction I still need to let it get 'better' anyways and it still needs to sit?

I did a salt bar just now with pumpkin and did 25% water. Turned out great but I'm wondering how this reduction will really help me in the end.

Using a stronger lye solution (less water) does make the bar harder. A physically harder bar will last longer because it does not abrade away as fast on the washcloth.

This assumes you are comparing harder and softer bars made with the same blend of fats. If you compare bars made with a different fat composition, this rule of thumb might not hold as true, because solubility comes into play too.

I do not shortcut the cure for the best results. Even if you choose to ignore the mysterious cure process, a soap made with a stronger lye solution still needs to dry enough to reach a stable moisture content and that takes at least 4 weeks.

DeeAnna said:

Using a stronger lye solution (less water) does make the bar harder. A physically harder bar will last longer because it does not abrade away as fast on the washcloth.

This assumes you are comparing harder and softer bars made with the same blend of fats. If you compare bars made with a different fat composition, this rule of thumb might not hold as true, because solubility comes into play too.

I do not shortcut the cure for the best results. Even if you choose to ignore the mysterious cure process, a soap made with a stronger lye solution still needs to dry enough to reach a stable moisture content and that takes at least 4 weeks.

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Hello Jenneelk! I agree with DeeAnna. No matter how much water is used we should wait at least 4 weeks and more. If we take the time and materials to make a good soap then I think we should not sabotage the results by trying to speed up a cure. Curing is a major part of the soap making process. It's also the most difficult for we are all very impatient. We have to learn to wait. I have seen this written many times that soap making is like making excellent wine - it takes time to make a good "vintage".

Thanks. I'm ok with waiting but thought there must be some benefit to a water discount since I know many use them. And if you still need to cure for 4-6 weeks so the bar is nicer.. then why discount water? That was kinda what I was wondering.

Maybe just for un-molding purposes? That would kinda make sense I guess.

I've seen other forums where people think it does shorten cure time and sell bars that have cured less than 4 weeks.

I discount and cure for 4 weeks, but have rushed that to 1 or 2 weeks in a pinch. I saw no difference. I've experimented and packaged 1 week old soap in cello and kept it for a year to see what would happen and it was just fine.

However, the recipe you're using may make your results vary.

Besides, most of the time the bar will be sitting somewhere not being used for quite some time anyway. I don't as a general rule put bars cured less than 4 weeks in my Rubbermaid boxes or cello bags.

jenneelk said:

Maybe just for un-molding purposes?

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A more concentrated lye solution tends to accelerate trace so it's a good strategy to use especially with slower tracing recipes.

Less water in the soap batter reduces the chance that the soap emulsion will "break". I'm sure you've read posts by beginning soapers who bemoan their soap has separated in the mold and made a lye-heavy, oily mess. If you keep track, you'll learn that most of them are using "full water" recipes and may not have mixed the batter quite long enough or thoroughly enough.

As Dagmar said, the soap is harder after saponification so it will be easier to unmold and/or can be unmolded sooner.

The soap may remain slightly harder even after a 4 week cure than a higher-water soap.

The soap will shrink less during cure.

All nice reasons, but YYMV.

I'm going to just shoot a non-experienced reply to this. If you did a discount and still waited the 4 weeks, you still end up with less water in your bars in the end anyway. You may not have sped up the cure process but you still end up with less water and a harder bar as the result. I am kind of curious though. I'm sure it may be preference, but do people typically tend to like the harder bars more? I know they are nice because the last longer and I'm sure that's desirable. But as far as having a hard bar versus a soft bar, is that also more desirable?

Crazy8 said:

I'm going to just shoot a non-experienced reply to this. If you did a discount and still waited the 4 weeks, you still end up with less water in your bars in the end anyway. You may not have sped up the cure process but you still end up with less water and a harder bar as the result. I am kind of curious though. I'm sure it may be preference, but do people typically tend to like the harder bars more? I know they are nice because the last longer and I'm sure that's desirable. But as far as having a hard bar versus a soft bar, is that also more desirable?

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A hard bar of soap is the most desirable IMO. If I sold soft bars of soap that hadn't had a 6-8 week cure time, I wouldn't have any repeat customers. One of the most popular comments at my booth is the fact that the customer bought some natural soap from a different vendor and it turned into a soggy mess in their shower which then in turn turned them off of natural soap.

A soft bar will turn into a soggy mess in your shower. A hard bar will last much longer and not make a mess.

Makes perfect sense to me. I guess when I am formulating my recipes and start getting the hang of it, I can start developing them to be harder. I have a number of men already getting interested in my warez and plans with all of this, so this is good to know. Didn't want to hijack the thread or anything so thanks for the info. No back to your regularly scheduled program...

There are two issues in soap longevity -- hardness and solubility.

Hardness is a physical characteristic -- is the soap hard like brick or soft like clay? Hard soap will not abrade away on the washcloth as fast as a softer soap. Although most people think a hard soap is a long lasting soap, that will be true only if the soap is not overly soluble in water as well.

Solubility is a chemical thing -- how fast does the soap absorb water and/or dissolve in water? A more soluble soap will disappear quicker in water and a less soluble soap will not. An indicator of solubility is how quickly the soap soaks up water if left sitting in a wet soap dish. Low water solubility sounds like a good thing for a long lasting soap, but it has to be coupled with reasonable hardness as well.

A soap made with "brittle" fats -- coconut oil or palm kernel oil -- will be relatively hard ... but it will also be very soluble. The traditional "cold water" or "hard water" or marine (salt water) soap is a coconut or palm kernel soap known for it's abundant lather.

A soap made with soft liquid oils -- monounsaturated oils (olive, almond) or polyunsaturated oils (safflower, sunflower, corn, etc.) -- will not typically be a hard soap, but it will be a less soluble soap. As the water temperature goes up, however, so does solubility, so soaps made with some unsaturated fats will lather better and clean better in warm to hot water.

The base oil in a typical soap recipe should be the firm solid fats -- palm, lard, tallow, etc. -- with high levels of palmitic and stearic fatty acids. Soap made from these oils are abrasion resistant and not overly soluble. This type of soap can be mild, hard, and long lasting, but the lather can be minimal especially in hard or cold water.

So how to make a long lasting soap that is nice to use? Lots of ways, obviously, as all the discussion on this forum shows.

But one approach is to choose a firm solid fat as the base oil in the recipe to add firmness and longevity. Include some brittle fat to increase the lather, get better performance in cold or hard water, and add to the physical hardness. Add liquid oil to add some mildness and good performance when used in warm to hot water.

And finally look at additives that can add to the properties you want to enhance -- sodium lactate for hardness, sugar for more lather, a chelator (citrate or EDTA) to reduce soap scum, etc.

Thanks for the explanation, DeeAnna. Another thing to consider is that if too much of your fats are very hard it seems to suppress scent. So I do like to have at least a third liquid oils.

Just for my own information I have been tracking the weight of two bars from the day they were made. One was made with the full default amount of water that SoapCalc uses, 38% of oil weight. The other was made with a 2:1 water to lye ratio, which works out to a water weight about 28% of oil weight. As you can see from the plot of the data, at every age the full water bar had a higher amount of residual water than the water-discounted bar. Which makes sense...the more water you start with, the longer it takes to dry out. Also interesting is that at 4 weeks the bars have lost only about half their original water and the loss is continuing, although slowing down even after 14 weeks. The chart is plotted as percent of water-free weight, so 100 on the Y-axis would be completely dry.

I would not vouch for the accuracy of this data in court, but as an experiment it is interesting. The two bars were from different batches but were made with the same recipe (apart from having slightly different FOs), so the composition of the oils should not be a factor.

Based on this I am thinking that my standard 4-week dry time may not be quite long enough, and these bars were drying in an upstairs room through a hot summer. In winter I would expect it to take even longer.

Timber -- here are similar data to compare with yours: http://www.soapmakingforum.com/showthread.php?t=35831

DeeAnna said:

Timber -- here are similar data to compare with yours: http://www.soapmakingforum.com/showthread.php?t=35831

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Thanks DeeAnna, that's interesting. My % weight loss curve was a little steeper than yours (at 50 days I was at 86-88% of original weight) but the shape of the curve is similar. The fastest water loss was in the first 14 days, as your results also showed.

It's nice to see similar results from completely different situations. I didn't formally weigh my test soaps after 50 days, but I do know they continued to lose weight-- a rough clue is that the cigar bands I put on the soaps after 50 days became very loose in the weeks that followed.

One of the criticisms of my little experiment when I shared it on SMF is that I was keeping my soaps in the bathroom (an airy well-ventilated room compared to most bathrooms). I'd say the continuing weight loss and the results comparable to yours are proofs my bathroom isn't too bad of a place to keep my soaps.

If anything, your environment is probably more representative of actual use. But it looks like we will get to a usable water content eventually either way; it just might take a little longer in a humid area. One thing that was interesting to me is that the little hump in the middle of my data plot coincided with a cool rainy spell we had. When the weather warmed back up the water loss accelerated again. (Both bars responded similarly; they are not time-aligned in the graph because they actually had different starting dates.)

I don't know if my testers will ever completely dry out; I plan to keep the plot going until the curve essentially flattens out and see where that is. I expect it to stabilize at some low, but non-zero value. I have a theory that the more water the soap loses, the shrinkage causes the structure of the soap to tighten up which makes it progressively more difficult for the remaining water to escape.

Here is the dry time graph updated through today. My test bars are still losing weight incrementally, but the curve has really flattened out. Interestingly, the bar with the higher original water content has stayed higher throughout the dry time and appears to be reaching equilibrium several percentage points above the other bar. I would have expected it to catch up at some point. Granted, this is one trial so no trend has been established, but I find it interesting. I think I see distinct phases in the curves, with a high rate of loss in the first 3 weeks, then a secondary phase from 3-14 weeks. At about 100 days the rate flattens again with much slower changes from then on.

Keep in mind that solid bar soap is not a solid like a block of metal is solid. Solid soap is an unusual water-in-soap colloid. What this means is water molecules are held inside a regular structure of soap molecules. Water can migrate out of the soap up to a point, but some is going to be deeply trapped within the soap structure. This trapped water will never ... or only very slowly ... migrate to the surface and evaporate out of the bar. The upshot is if you start with more water in the soap at the time it's made, some of that "extra" water will remain trapped within the soap structure, which is what you're seeing with your two soaps. Nice work!

Which is the minimum quantity of water you can use for, let say, 100g of lye?