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"Real" Calculations RE: Water Hardness and Sodium Citrate

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BrewerGeorge

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Sorry if it seems like I'm spamming questions but finding people with ACTUAL knowledge after so many weeks searching through the wilderness of the Internet has me a bit giddy. ;)

We have softened water at home so scum hasn't been an issue, but my daughter has asked me to make her some (vegan) soap and she does not enjoy soft water. The water here in central Indiana is HARD. So hard that I have to add acid to brew a stout, if that means anything to you. If it doesn't, think Indiana limestone. H. A. R. D.

I've now read all the threads about using chelaters and seen the typical usage rates, but I'm wondering if anybody has done the math to relate actual ppm of Hardness to the amount of sodium citrate needed to counteract it. (I have sodium citrate on hand for making cheese sauces...) I send water samples for testing periodically because I need to know exact numbers for brewing. Can I use this info to calculate a good starting point for sodium citrate? And is there any downside to using too much?

Thanks again!
 

ngian

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Hello

Soft water isn't about how hard the water is? Maybe your daughter does not enjoy the soap film that is very noticable on long hair, and palmitic/stearic fatty acids makes this phenomenon more intense. And I think that chelators can't do anything with soap film.

In my humble opinion it is generally better to have a water softener at your bathroom instead of adding over 3-5% of sodium citrate or EDTA without knowing how the bar will be. I think that the chelators can't cope up with the gallons / litres of hard water that will be flowing on us.

I also have hard water

Units | mg/l Calcium carbonate
Maximum value | 250
Minimum value |
150

and I only have a little problem bathing long hair (my little daughter's hair). Sodium citrate is what I use at 3% of oils, and I've seen bigger bubbles and that makes me feel that soap is working a bit better/easier.

Hope that someone else will chime in and answer you about the calculations you seek...

Nikos
 
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BrewerGeorge

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Hello

Soft water isn't about how hard the water is? Maybe your daughter does not enjoy the soap film that is very noticable on long hair, and palmitic/stearic fatty acids makes this phenomenon more intense. And I think that chelators can't do anything with soap film....
Sorry if I wasn't clear. When I said she didn't enjoy soft water above, I just meant that her house didn't have it. She grew up with it and would love to have it, but it's not an option at her rental house.
 

DeeAnna

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I personally do not think you can "use a formula" to neatly relate water hardness to the dosage of EDTA or citrate you would add to soap. I also know (from having done the calculations) that if you try to add enough chelator to a soap to absolutely treat all the anticipated "hard water" ions in the water, you'll end up with chelator being a huge percentage of the soap. That's not realistic nor necessary.

The chelator in the soap needs to treat only the water that comes in direct contact with the soap and only for the time the soap is also in contact with whatever body part is being washed. How much water that is and how much time that it will vary greatly depending on how the soap is being used, the body parts being washed (hands vs. body skin vs. hair), running water (shower) vs. still water (bath), etc.

The worst case scenario is soap for the laundry or hand dishwashing. In those cases, the chelator should theoretically treat the entire body of water in the washing machine tub or dish pan, but again we're back in the impractial situation where the chelator is a large % of the soap. Situations like this are really the province of a whole-house water softener or the use of a zeolite water softener additive that is measured into the washing machine tub or bath tub (http://www.amazon.com/dp/B004VL3ZPQ/?tag=skimlinks_replacement-20).

Going back to the use of a chelator in bar soap -- it really IS a bit of a trial and error matter depending on the hardness of the water, how the soap is used, and the preference of the bather.
 
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