Sodium Citrate or Tetrasodium EDTA

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It is my understanding that used in soap-making, both Sodium Citrate and Tetrasodium EDTA act as chelating agents. I would like to know however if Sodium Citrate is also effective as a DOS inhibitor in the same way Tetrasodium EDTA is.

I have Sodium Citrate and would like to use it if it is useful for both cheating and DOS.
 
From what I've seen, most people are using 2% to 3% citric acid ppo (20 to 30 grams citric acid per 1000 grams of fat) plus the appropriate extra amount of lye. Maybe others can chime in with their preference.

If using sodium citrate, then the equivalent dosage is 2.6% to 3.9% citrate ppo (26 to 39 grams citrate per 1000 grams of fat). No extra lye is needed if using sodium citrate.

These dosages are for controlling soap scum as well as reducing the chance of DOS. Use more for hard water, less for soft.

If you only want to use citrate for DOS control in bar soap, then you can go much, much lower in dosage. More info here: http://classicbells.com/soap/citricAcid.html
 
From what I've seen, most people are using 2% to 3% citric acid ppo (20 to 30 grams citric acid per 1000 grams of fat) plus the appropriate extra amount of lye. Maybe others can chime in with their preference.

If using sodium citrate, then the equivalent dosage is 2.6% to 3.9% citrate ppo (26 to 39 grams citrate per 1000 grams of fat). No extra lye is needed if using sodium citrate.

These dosages are for controlling soap scum as well as reducing the chance of DOS. Use more for hard water, less for soft.

If you only want to use citrate for DOS control in bar soap, then you can go much, much lower in dosage. More info here: http://classicbells.com/soap/citricAcid.html


Thanks DeeAnna - I haven't seen that source. I have Kevin's book and read the part about sodium citrate not seeming to help with DOS. The link you posted says that some soapmakers think it does. Well, I use s. citrate for scum reasons, and if it help dos - all the better. I'm seem to be discovering that my recipe tends to dos after 9 - 12 months. Still observing. Not sure what route I want to take if dos remains a problem as I want to avoid EDTA. I have yet to use ROE. (should probably start testing that soon)
 
The link I gave is to my website. I have started to store some of my answers there so it's easier to reply to questions people ask a lot. Not to say my stuff is the last word, however. I'm always learning. :)
 
I was just looking at Dr. Dunn's book (page 284). His experiments showed that sodium citrate alone did not help much at all with DOS, but when used together with BHT, it worked great at keeping DOS at bay. :thumbup:


IrishLass :)
 
I was just looking at Dr. Dunn's book (page 284). His experiments showed that sodium citrate alone did not help much at all with DOS, but when used together with BHT, it worked great at keeping DOS at bay. :thumbup:


IrishLass :)


That's right, I forgot about BHT. But I'm concerned about its safety. The lard and some of the tallow I buy has bht, but I've turned a mostly blind eye to that simply because the alternative is so expensive. But adding more bht is something I hope to avoid.

On the other hand, if I knew a really smart chemist type person who knew if bht survived lye or not, I would ask their opinion! Now, where would I fine one...?:think:
 
Yep, I saw that too, IL. But I'd say BHT is perceived to be even less "crunchy" than EDTA, so I honestly doubt someone who wants to use citrate with the idea it's more "natural" will also jump on the BHT bandwagon.

What puzzles me is that people here on SMF are seeing reasonable results from citrate, despite what Dunn's findings showed. He used less citrate, however -- I think he tried 1 g per 1000 g oils and (edit) was only looking at color change as an indicator of possible DOS, not at actual evidence of DOS. (end edit) Folks here are using considerably more (1% to 3% ppo) with the goal of scum control. This may be the difference between his conclusion about citrate vs. the opinions of soapers here.

ETA: Lenarenee -- according to Dunn, yes, BHT does survive the lye -- at least enough so it helps prevent DOS in soap. I've not used BHT, so I'm just passing on info from a reliable source.
 
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He used less citrate, however -- I think he tried 1 g per 1000 g oils. Folks here are using considerably more (1% to 3% ppo) with the goal of scum control. This may be the difference between his conclusion about citrate vs. the opinions of soapers here.

Good point! :thumbup:


IrishLass :)
 
I was just looking at Dr. Dunn's book (page 284). His experiments showed that sodium citrate alone did not help much at all with DOS, but when used together with BHT, it worked great at keeping DOS at bay. :thumbup:


IrishLass :)

Any information about BHA and soap? The Walmart shortening that is usually around half of my recipes has both BHA and citric acid, and I'm proactively adding sodium citrate as well.
 
Yep, I saw that too, IL. But I'd say BHT is perceived to be even "crunchy" than EDTA, so I honestly doubt someone who wants to use citrate with the idea it's more "natural" will also jump on the BHT bandwagon.

What puzzles me is that people here on SMF are seeing reasonable results from citrate, despite what Dunn's findings showed. He used less citrate, however -- I think he tried 1 g per 1000 g oils. Folks here are using considerably more (1% to 3% ppo) with the goal of scum control. This may be the difference between his conclusion about citrate vs. the opinions of soapers here.

ETA: Lenarenee -- according to Dunn, yes, BHT does survive the lye -- at least enough so it helps prevent DOS in soap. I've not used BHT, so I'm just passing on info from a reliable source.

Interesting. Wonder if the BHT in packaged lard has any carry over affect (effect?) to the soap (60 to 75% lard). I've been using 2% sodium citrate for about 6 months, too early to tell how it does for dos.

On the other hand, its also to early for me to know if high lard does suffer more dos. I've only been soaping 21 months, high lard only a year, and initially 1 lb batches only, and now 4 lbs at a time. Still very much a learning process.
 
"...Wonder if the BHT in packaged lard has any carry over affect (effect?) to the soap (60 to 75% lard)...."

Yes, it should. Whether the dosage is high enough to have an effect in your soap -- dunno the answer to that one!

I have always used store-bought lard until recently and most of my recipes have been at least 50% lard right from the start (started actually making soap about 3 years ago). I began to use EDTA, oh, maybe a year ago based on suggestions made by Irish Lass. It definitely helps with soap scum. EDTA also seems to prevent the occasional freckles of DOS that come from specks of impurities, although I want to keep evaluating my soaps as they age before deciding this is a good conclusion to draw.
 
In researching my answer to another thread, I came across these tidbits that might be interesting additions to this thread:

"...The formulation of soap bars has become more complex over the years due to an ever-increasing number of soap bases that incorporate more and more additives. The “green” and “natural” market segments have led to soap products with new materials. Also, consumers have become more accustomed to multifunctional products offered by the cosmetic industry, including conditioning shampoos, antiperspirants, sunscreens, lotions, and creams.

"Traditional soaps were designed for cleaning skin and clothes, but as time passed soaps came to be used as a delivery system for perfumes and superfatting agents. Today, the cleansing aspect seems almost secondary to the effects of the various additives that are delivered through the soap system.

"...Antioxidants are useful as fat, oil, and fatty acid preservatives. However, when these materials are converted to soap, we have found that chelators provide better protection than antioxidants such as BHT.

"We have found that as a preservative in traditional soap systems at a pH of 10, chelators provide better protection than antioxidants such as BHT. Additionally, BHT can cause severe yellowing of soap products when stored under certain wrapping and warehouse conditions. It is hypothesized that certain quinones form when BHT reacts with nitrogen-based exhaust products produced by warehouse motor trucks and lifts, which lead to the undesirable yellowing.

"Virtually all of the preservatives listed in Table 4.1 are chelators. This is because pro-oxidant metals, such as iron, copper, zinc, and magnesium, have extremely negative effects on soap chemical stability, and therefore need to be deactivated. Pentasodium pentetate and tetrasodium etidronate are particularly effective preservatives for color and odor stability in these systems, and are often needed at levels below 0.10% for each.

"Chelators may be most functional when used in combination, depending on the type of metals ... needing to be chelated. A single chelator may only be effective against certain metals and not at all effective against others. The formulator must be familiar with these properties in order to develop additive packages that are stable and functional...."

Source: George, ED, and DJ Raymond. Formulation of Traditional Soap Cleansing Systems. Chapter 4 in Soap Manufacturing Technology. Spitz, L, editor. Emphasis is mine (DeeAnna).

soap preservatives Soap Mfg Tech Spitz L.jpg
 
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