Soap Tester/ Soap Scum and Oils

[loriag]

So I asked a co-worker about the soap I gave her to test out. The recipe was one of the first I tried so it contained 22.2% CO, 22.2 PO and 55.6 OO. She was hesitant to tell me it felt fine but she had more soap scum to clean out of her tub with this soap than other handmade soaps she has tried from bigger companies. She is fanatical about cleaning and baths twice a day. She said it was harder to clean her tub, she had to scrub more with a magic eraser with using my soap.
Since this recipe and batch (that I gave her) I have been adding EDTA. So today I gave her a bar with the EDTA and asked her to see if she noticed a difference. She will be a good one to test this. I shower and really don't notice any issues but only clean my tub weekly. She would clean hers much more often, I wonder if it isn't daily.
Now all this to also ask do certain oils contribute to soap scum from handmade soap or is it just hard water? Do higher percentages of certain oils affect soap scum and handmade soap? I didn't think we had hard water but I am not 100 % sure. I just find this all interesting and am glad that she was honest when asked.

 

[Obsidian]

I notice more scum with lard but using a chelator fixes that right up.

 

[DeeAnna]

Unless you and your friend are both bathing in rain water or distilled water, there will always be some calcium and magnesium in your water. This will always be true even if the water has been artificially softened or comes from a source of water that is not especially high in these minerals. Soft water is not the same as no-mineral water. It's just less mineral-y water. The calcium and magnesium minerals in tap water are the culprits that make soap scum when mixed with lye-based soap.

Your friend is always going to notice more soap scum when she takes baths than you are when you shower. When you shower, a chelator has the responsibility to bind up the calcium and magnesium just in the soapy water on your skin and washcloth. A good chelator added to your soap does a decent (not perfect, but good enough) job of this. Your skin will not be sticky from the scum and there will be less scum on your shower.

When you bathe in a tub of water, a chelator has to be strong enough to treat all the water in the bathtub to bind up the minerals in the water and prevent soap scum from forming and sticking to your skin and tub. That's not going to happen. Your friend would need to add a separate water softening product such as Calgon to the bath water to soften it and reduce scum. She could certainly also use a soap with a chelator as well.

Why would your soap cause more scum than other soap? One thing is perception. Your friend is not in a "blind" scientific study of your soap vs the others she has used, so some of her thought that there's more scum could be subjective opinion. She knows she's using your soap and that knowledge might create some unconscious bias.

There might also be objective reasons for her perception. If your soap is more water soluble and/or physically softer than the other soaps she has been using, there will be more of your soap present in her bath water. More soap in the water means more soap to react with the minerals and thus more soap scum.

edit: Also soap with a high superfat will tend to create more buildup in the tub or shower. I suspect it's because the soap cannot sufficiently emulsify the extra fat so it doesn't wash down the drain properly. Instead, some of this excess fat combines with soap scum to stick to the shower or tub and your plumbing. end edit

Another thing to keep in mind is that those "bigger companies" may not be selling just plain lye-based soap even if they call it "soap." Hand crafted soap can contain synthetic detergents too -- you have to read the ingredients list to know for sure. Syndets don't make soap scum.

 

[zanzalawi]

When you bathe in a tub of water, a chelator has to be strong enough to treat all the water in the bathtub to bind up the minerals in the water and prevent soap scum from forming and sticking to your skin and tub. That's not going to happen. Your friend would need to add a separate water softening product such as Calgon to the bath water to soften it and reduce scum. She could certainly also use a soap with a chelator as well.

this is a very helpful post for it, shifted my perception of the best job a chelator can possibly do, thanks much!

 

[penelopejane]

What DeeAnna said plus for me a lower SF reduces soap scum and a chelator like citric acid. Also cure time effects soap scum and the length of time you shower for and whether you really dry the soap between uses. A friend stands my soaps on end and her bathroom is really breezy and my soap stays rock hard and lasts for ages longer for her than it does for me.

 

[loriag]

Thanks DeeAnna, I always appreciate your thoughts, as well as everyone else's.
I SF at 3% usually, maybe I should drop it to 2%. Originally I was not SF'ing at all. My cousin who was my help to get started doesn't SF. I don't have any issues with 0% SF but decided to add just a bit for possible mishaps. My tester liked how long my bar lasted, so that was good. I asked her to bring me some of her labels if she had any for the other soap she has used.
My soaps last a long time for me as I use a wire holder that lets them drain well and dry. In fact I have 3 wire holders to accommodate all the bars I like to use in the shower.

 

[Lee242]

What are some good chelators?

 

[dibbles]

What are some good chelators?

If you search this forum, you will find lots of threads on chelators. Sodium Citrate and Tetrasodium EDTA are the most often recommended. You can also use citric acid, but will need to add additional NaOH. And here is a link to DeeAnna's explanation: https://classicbells.com/soap/chelator.html

 

[Zany_in_CO]

Your friend would need to add a separate water softening product such as Calgon to the bath water to soften it and reduce scum.

I prefer baths to showers and Calgon or similar water softener is great for reducing soap scum. TIP from DIL: Use cheap hair conditioner to wipe down the tub after you get out. Works like a charm!

 

[loriag]

When you bathe in a tub of water, a chelator has to be strong enough to treat all the water in the bathtub to bind up the minerals in the water and prevent soap scum from forming and sticking to your skin and tub. That's not going to happen. Your friend would need to add a separate water softening product such as Calgon to the bath water to soften it and reduce scum. She could certainly also use a soap with a chelator as well.

My friend did not notice any difference with the soap with EDTA in the tub. I told her she may have to start using Calgon! Now my other boss, raved about the soap I gave her. May just have another handmade soap convert!

 

[Lee242]

EDTA, citric acid, sodium gluconate, sodium lactate, sodium citrate
I have never used any of these in my soap and just ran across this on chelating, interesting, so I take it that salt is not the same. My question is when to use this or is there a time not to use it or just personal choice?

 

[DeeAnna]

Normal table salt (NaCl) is not a chelator, nor is sodium lactate. And citric acid is not strictly a chelator until it reacts with NaOH (or KOH or other alkali) to form citrate, a salt as chemists define a salt (aka sodium citrate or potassium citrate).

Whether or not to use a chelator is a personal choice but there are clear advantages to using one. It greatly reduces the chance of DOS (rancidity) in your soap that is caused by metallic contamination. It reduces soap scum at the sink or in the shower, although a chelator in soap will not reduce soap scum as effectively if used in the laundry or the bathtub, as I mentioned above.