Additive to prevent soap bar from dissolving too quickly?

[Doug]

Hi.

When rubbing a soap bar with my hands, it seems some soaps dissolve faster than others. Or, when sitting in a soap dish, some bars of soap quickly turn to mush.

Is there an additive that can be added to slow down this dissolving so the soap bar doesn't rub off so quickly?

Thanks,
Doug in Oakland, CA

 

[earlene]

Two things:

Recipe: What are your recipes, specifically? Depending on the formula of the soap, some are going to melt away faster than others. Some are going to be longer lasting than others. So what are your recipes for the ones that perform as you describe?

Soap dish/storage method: How you store your soap between uses matters a lot for the life of your soap. It is best for soap to be stored on a self-draining soap dish with good air flow around it to facilitate drying between uses. Sitting in a soap dish with no way for the water to drain off will create a wet bar of soap. Some soaps are prone to attact water (recipe matters here), while others are less so, but regardless, all soap will last longer if kept dry between uses, rather than wet.

 

[shunt2011]

If you share your recipe and process we would be better able to help you. My soaps last a good long time in the shower.

 

[cmzaha]

My soaps last around 30 showers and if used as a hand soap they last 2-3 months. Of course it depends on the fatty acid profile of the bar, how it is stored, how it it used etc. As Shunt mentioned if you post your recipe we can troubleshoot it.

 

[lsg]

Sodium lactate and stearic acid will make a harder bar. You might also try adding a little bees wax or soy wax to the recipe. A bar lower in oleic fatty acids will also last longer.

 

[Rune]

Add more hard oils and less soft oils in your recipe. Add sodium lactate or vinegar to the lye water. If using vinegar, you have to do some calculations or use a lye calculator that does the maths for you, like soapmakingfriend.com.
Also don't use a too high percent of superfatting.

I don't know your recipe, how much soft and hard oils you use, which oils and your level of superfat. But keep in mind that if your lye is not very pure (for example have become lumpy from soaking moisture from the air), then your superfat will be even higher than you think it is. The same if you add acids without adding extra lye. Tomato juice, for example. Or add extra fat but not include it. For example coconut cream.

If you have many oils, butters and fats to choose from where you live, it might be possible to replace one or two oils in your recipe with something that has a higher percentage of stearic acid. If not, you can add some in the form of soy wax, for example. Pure stearic acid can be almost impossible to soap with in cold process, depending on how much you add.

And yes, use a good soap dish. I have a very, very good one, one that is not a soap dish at all, but anyway as perfect as it can be! It is a refill for an old style dishwashing brush, turned upside-down. When it gets dirty with soap, just wet it and wash the sink with it, then rinse and shake and it is good as new. Looks stylish too, plus very space saving. It is one of these (just turn it upside down and place te soap on the brushes. The soap will not slide off):

 

[Obsidian]

Doesn't matter how hard soap is, if left in a wet dish it will get soggy. I even have issues with plastic or wooden soap dishes, I have to keep mine on wire racks in the shower.

 

[bluethegrappler]

Keep in mind that not all hard oils make a long-lasting soap. Coconut oil is high in lauric and myristic acids, which make a hard soap but one that dissolves quickly. Stearic and palmitic acids, on the other hand, contribute to a long-lasting bar. If you use the Soapee calculator, it has a longevity property to help with this.

Of course, proper storage, letting the soap dry between uses, and ensuring it is properly cured before use is important. Any soap will turn into a soggy mess if is left sitting in a puddle.

 

[linne1gi]

I've heard there's a formula for determining how long your soap will last. The hardness factor minus the bubbly factor. Is this correct?

 

[Rune]

I have no idea if that is correct or not, but it sounds very logical, since you will get more bubbles the more easily the soap can dissolve in water.

 

[DeeAnna]

Hardness = % stearic + % palmitic + % lauric + % myristic
Bubbly = % lauric + % myristic
"Longevity" = % stearic + % palmitic = Hardness - Bubbly

Stearic and palmitic fatty acids reduce the water solubility and add hardness to your soap. Lauric + myristic acids also add hardness but increase the water solubility. So if you want a hard soap that also has a longer life, you will want a reasonably high % of stearic and palmitic acids and a reasonably low % of lauric and myristic acids.

The Soapee soap calc and I believe the new SMF soap calc have longevity included in their calculations. SoapCalc and most older soap recipe calcs do not.

edit: But the fatty acid profile is not the only factor in getting a long lived soap. As others have pointed out, there are many other factors that affect longevity. These include letting the soap bar dry thoroughly between uses vs sitting in a puddle of water, a decently long cure, some additives such as salts that add hardness (examples: sodium lactate, sodium acetate made from vinegar, and sodium chloride (table salt)), the frequency of use, how the soap is used (for example, rubbing the bar against hairy skin rather than lathering up a cloth).

 

[glendam]

The lyecalc.com calculator also determines longevity of soap bar

 

[KiwiMoose]

How about salt water - brine?

 

[Rune]

The lyecalc.com calculator also determines longevity of soap bar

Oh my goodness what a great calculator that is! I have never seen that one before. It would have been perfect if they only done two things to improve it, added vinegar and did the calculations for much lye you have to add extra for citric acid, vinegar and other acidic additives. They do that (except for vinegar, which is not represented), but they don't add it to the total lye. So you have to do the calculations yourself, it seems.

 

[Steven]

How about salt water - brine?

@KiwiMoose - I am also curious about salt water. I've been coming to the conclusion that CO is really drying for me based on my first couple recipes. Been reading about gentle(r) bars of soap (Zany's no slime castile and Genny's shampoo bar) and thinking about doing a hybrid of the two for a regular bar of soap. A modified genny's recipe (>10% CO) with some salt water seems like a good experiment. I read an old post from @IrishLass where she commented that salt water seems to help with the initial hardening/setting of the bar, but long term there was no noticeable difference between a bar with brine and without (in terms of hardness and longevity). The plot thickens! Curious what others have to say...

 

[Rune]

Less CO and adding salt, wouldn't that mean less lather? What about less CO, add sodium lactate and/or replace the water or some of the water with vinegar, perhaps add a little sugar, use slightly more castor oil and use dual lye, 95% NaOh and 5% KOH. Perhaps you can omit CO alltogether and try palm kernel oil as a replacer? Some say that helps, I don't know.

 

[Arimara]

Salt water nets you a harder bar. If bubbles are a concern, you can make a simple syrup at a ration of 1:1 water to sugar and us a tsp or a tbsp of it per lb oils. You can also just be lazy and get some castor oil and use 3-5% of it in your soap recipe.

 

[KiwiMoose]

@Dawni posted a really good time-lapse video of a brine bar versus a regular bar she might be able to locate for us.
I've recently made a 25% (salt to water ratio) brine bar with added sugar (1tsp PPO) AND 5% castor. Not ready for testing yet (it still has 20% coconut oil though).

 

[Dawni]

Hi guys.. This is that time-lapse page Incidentally, I had posted that in a thread that talks about salt n hardness and there's good info in there.

Most info I've read regarding soleseife says to up the coconut in any regular recipe because the brine will cut lather. I have a feeling even if you use a low amount, you'd still get bubbles with sugar and/or castor oil like KiwiMoose had done.

Now regarding regular amounts of salt and longevity, I can't say. I have yet to test a bar specifically for that.

I will point out one thing that hasn't been mentioned. A big factor is storing your soap between uses but I feel a bigger factor is how you use it. I compare my soap that my mom currently uses (high lard) and one I am using (high canola) that we started on the same day.

While mine gets oleic gel (I need to clarify that I would not class this as slime), which I wipe off and soap with, the rest of the bar is still hard and not much smaller than when I first used it a week or so ago. Hers is significantly smaller.

Why? She has the water running on while she lathers the bar all over, whereas I turn off the shower when I soap and I lather in my hands and then proceed soaping the rest of me. I've noticed it's the same no matter what soap she uses lol

Just something else to think about..

 

[glendam]

Oh my goodness what a great calculator that is! I have never seen that one before. It would have been perfect if they only done two things to improve it, added vinegar and did the calculations for much lye you have to add extra for citric acid, vinegar and other acidic additives. They do that (except for vinegar, which is not represented), but they don't add it to the total lye. So you have to do the calculations yourself, it seems.

The guy who developed it might be able to add that. I will copy your message and let him know. (His name is Jeff). I have added citric acid on the past for soap scum but lately I switched to EDTA, but there is probably a way to select which additives you want added to your total. It’s the lye calculator I prefer, I like the visual representation of the soap number values