Yes, Virginia, you CAN make a 50% EDTA solution!

[DeeAnna]

Tetrasodium EDTA (just EDTA for short) is a chelator that protects soap from rancidity (also called DOS or Dreaded Orange Spots). It also reduces the amount of soap scum created when soap is used in hard water.

EDTA is usually available from suppliers as a powder, but because so very little is needed, it's easier and more convenient to make a mixture of water and EDTA and measure that instead. When I first started using EDTA, I accepted the common wisdom that the highest concentration of EDTA that could be dissolved in water was 39%. Turns out that isn't the case.

I came across some info recently from Sigma Aldrich who makes EDTA. The tech sheet I looked at suggested tetrasodium EDTA can be made into a solution with water at up to a 55% concentration (55 grams EDTA plus enough water to make a total of 100 grams of solution). I thought, hey, a 50% solution would make the math simpler, so I tried it.

I'm now here to tell ya ... it really does work. The EDTA powder takes awhile completely dissolve at a 50% concentration. To help it dissolve, I warmed the water slightly (warm to the touch -- maybe 95 F, 35 C) as well as stirred for minute or so. I do not think the warmth is strictly necessary, however. Just a little patience is all that's needed.

The solution remained cloudy for several minutes after the powder was obviously dissolved, but the cloudiness looked more like fine gas bubbles rather than solid particles. After about 5 minutes, the solution became clear. Now that several days have passed, I can confirm that all of the EDTA has stayed in solution and the mixture has remained crystal clear.

So ... there ya go. Have fun with it. :mrgreen:

More about using EDTA in soap -- http://classicbells.com/soap/EDTA.html

Geek background about "The 39% Solution" -- The 39% concentration comes from how EDTA is used in industry. It turns out 1 gram of 39% EDTA solution will chelate 1 millimoles of metal ions. When you are frequently adjusting the chelation dosage in an industrial process, such as treating the water used in steam boilers, then using an easy-to-remember number like this makes the calculations simpler and reduces the chance of error. For us soap makers, 39% is a pain in the patooty -- a 50% concentration makes more sense!

(Any Sherlock Holmes fans out there? I couldn't resist the allusion to "The 8% Solution".

 

[KristaY]

Once again DeeAnna, you rock! I had math problems with the 39% solution and it was indeed and pain in the patooty.

I tried adding the granules to the lye water before the lye and it, of course, dissolved no problem, but I ended up with mad ash in the lye water. Then I tried adding the granules to the lye water after it was cool and it never fully dissolved so had to strain it out. I finally ended up mixing it separately for each batch which is time consuming and another pain in the patooty.

Then last week I mixed EDTA/water for a batch and realized I'd done a 50% solution and it dissolved just dandy. I didn't watch the progression because I was working on the oils, lye, other additives, etc, but saw it was clear when I was ready to add it. I quickly dumped it into my lye water then that into the oils because I was afraid it might fall out of suspension. Now I know I can mix a bigger batch without worry. Time saved, simple math, win-win.

Thanks DeeAnna!!!!! :razz:

 

[DeeAnna]

Yep, you can pre-mix your EDTA solution -- a <gasp!> EDTA masterbatch.

Just keep it in an airtight container to prevent evaporation. I use a squeeze bottle with a cap that has a flip spout. I also store it in a dark cupboard. I don't specifically know that it is sensitive to light, but there's no sense in inviting trouble.

 

[KristaY]

..."I don't specifically know that it is sensitive to light, but there's no sense in inviting trouble."

Good point. I was going to use the exact same bottle you described but I think I have colored ones. I usually leave my additives out on my counter in a specific spot that gets no direct sunlight but will get florescent light from my overhead work light. I guess I'd better find a darker storage spot just in case.

 

[DeeAnna]

Ah. I finally realized what additive I use that's light sensitive **** deleted ****

See Posts 8 and 9 below.

Sorry for any confusion.

 

[SoapSap]

How much of the 50% solution should be used per pound of oil?

 

[DeeAnna]

SoapSap -- More about using EDTA in soap -- http://classicbells.com/soap/EDTA.html

 

[KristaY]

Ah. I finally realized what additive I use that's light sensitive -- it's not EDTA, it's sodium lactate solution. I store my EDTA solution in a dark cabinet right next to my sodium lactate solution -- but it's the SL that does best in the dark.

Sorry for any confusion.

I had no idea SL was light sensitive! I don't remember reading it on any websites I buy from. It's always on my work counter, out of direct sunlight but exposed to my work light. What will happen with the light exposure? Decreased effectiveness? Chemical morph into something unpleasant? Now I'm seriously annoyed with myself I didn't know that.

I just went to WSP and looked at the MSDS for SL. Under "Chemical Stability" it says "Stable at ambient temperature and under normal conditions of use." Then I read "Conditions for safe storage, including any incompatibilities" which states "Take all necessary measures to avoid accidental discharge of products into drains and waterways due to the rupture of containers or transfer systems. Keep container tightly closed and dry. Protect from heat and direct sunlight. Keep away from ignition sources."

So based on the MSDS, is my SL okay being exposed to florescent lighting a few times a week, several hours at a time?

 

[DeeAnna]

I think I'm going to have to eat some crow on this point. I can't find the reference that led me to believe sodium lactate SOLUTION is light sensitive. The MSDS for SL powder at Lotioncrafter (where I bought my SL) doesn't mention this point either. I did find an MSDS from a manufacturer of SL -- it says the powder decomposes with exposure to light or high temps (much higher than we would ever use in soaping.) But that's still not saying anything about SL solution.

So ... Krista, thanks for pointing this out. I stand corrected. I am now going to stand in the corner for 10 minutes....

 

[Dahila]

I use 1400 oils or 2200 whole batch Deeanna can you check my calculation with 50/50 solution?
5 g per 1000 g
2 g per 400g
7 g Edta +7 g water = 14 g solution (50/50) for 1400 oils,

If I want to do it with whole batch it is 0.5% x 2200 then x 2 to get amount of 50/50 solution I need for this batch

2200 whole batch 11 g x 2=22 g of solution. I am not sure I do it right,

 

[DeeAnna]

"...7 g Edta +7 g water = 14 g solution (50/50) for 1400 oils..."

"...2200 whole batch 11 g x 2=22 g of solution...."

Your answers look correct to me, Dahlia. Well done -- bravo!

 

[Dahila]

Thank you so much DeeAnna <3

 

[SoapSap]

SoapSap -- More about using EDTA in soap -- http://classicbells.com/soap/EDTA.html

Thank you. This answers all of my questions.

 

[KristaY]

"I am now going to stand in the corner for 10 minutes...."

Well shoot! I'm sorry I didn't see this yesterday or I would have made you get out of that dang corner! Hopefully you took a glass of wine with you or a bag of cookies.

Basically we were just talking about different types of SL - yours is powder and mine is solution so just a bit of confusion on my part. So cough up those blasted feathers and get out of time out, it's all good!

 

[Arimara]

I think I will do myself the favor of writing .5% as.005 so I won't get confused like I've been for the last 10 minutes. I suck at math and my job doesn't make numbers any friendlier.

 

[DeeAnna]

Arimara -- When I taught "high school algebra for math phobic college students", I told my students (most of whom made it clear they did NOT want to be in algebra class) about how algebra is a language just like English or French.

The "per" in things like "miles per hour" was a clue that the English words were hinting at a division problem.

In English, we write "percent" all together nowadays, but it's one word made originally from two -- "per cent." The "cent" in "per cent" is like "100 cents in a dollar" or "100 years in a century".

So "per cent" or the symbol "%" means "a division problem where you divide by 100". So anywhere you see the % sign in English, to translate that to the language of Math, you'd want to divide by 100.

0.5% = 0.5 / 100 = 0.005

Krista -- Thanks for encouraging me to come out of that corner. I didn't stay there too long! I had a good day yesterday teaching a class on wet felting. It went pretty well and we had a lot of fun.