Irishlass - Can you tell me how much EDTA you use and how you incorporate it? I tried using it about a year ago and gave up since I could not dissolve it.
Thanks!
Sorry so late in responding! Just got back from a very lovely, much needed vacation.
For my soaps, I like to work from a master-batch 39% solution of EDTA that I make myself out of powdered Tetrasodium EDTA and warmed distilled water, which gets stored away in a plastic bottle with a flip-top cover to use as needed. I normally make 12 oz of the solution up at a time, which is plenty enough to last me through several 2.7 pound batches of soap (the size batches I normally make).
Why a 39% solution, you might ask?
Well, from all that I've read, a 39% solution is a good % for the Tetrasodium EDTA to be able to dissolve properly without precipitating out of solution during storage.....so that's the % solution that I make, and for what it's worth, it stays nicely dissolved for me and is very convenient to use.
To figure out the proper amounts of warmed distilled water and EDTA that I'll need in order to make enough 39% solution to fit inside my 12 oz. bottle, I like to use Roxanne's DWCP Water Calculator :
http://rivercitysoaps.com/dwcp/watercalc.php . I simply type '39' in the 'Desired Solution Strength' box, then I play around with the water and EDTA amounts until their combined weights equal out to as close as 12 oz as possible without going over (I use the 'Weight of Lye' box for the EDTA amount).
Once I've weighed out the proper amounts of each, I mix them together in my trusty lab beaker with pour spout (a measuring cup will work just as well), stirring until fully dissolved, then I pour the solution into my 12 oz. bottle, cover tightly, and store at room temp until needed. You can make a larger or smaller amount than 12 ounces by the way. I make 12 oz. simply for convenience sake because I happen to have lots of 12 oz bottles on hand.
No matter how much or how little of the solution you make, please make a note that the total weight of the finished 39% solution
in grams divided by the gram weight of the powdered EDTA with which you used to make the solution should always equal out to 2.56g. You don't need to overly concern yourself too much about that fact at this point in the discussion, but write it down in your notes, because it will come into play shortly.
The usage rate of EDTA that I like to use in my soap is .5% per my
entire batch weight (as opposed to just the ppo weight), but since I'm working from a 39% solution instead of adding straight-up/full-strength EDTA powder to my batch, I need to do a little bit of extra math to make sure I add enough of the solution to my batch that will equal out to a .5% amount of powdered EDTA. Here is how I calculate things out when working from a 39% solution (it's a simple 2-part equation):
1) First, I total up the weights of all my batch ingredients
in grams, including the gram weights of the FO, colorants, and any other additives I might add.
2) I then take that sum total batch weight in grams and multiply it by .5%. The resulting sum will be the amount of powdered EDTA in grams that is required for my batch.....oh, but wait.... my EDTA is in a 39% solution, so I'll need to do one more calculation to account for that. Do you remember that amount of 2.56g that I metioned a few paragraphs above? Well, now's the time to put it to good use. Take the resulting sum of powdered EDTA that you just calculated out when you multiplied the total batch weight in grams by .5%, and then multiply it by 2.56. The resulting sum from that is how much of the 39% solution in grams that you'll need to weigh out for your batch.
I like to add my EDTA solution to my batch right after I add in the lye solution. It mixes in quite nicely for me without any problems.
I hope that helps! It all may sound confusing at first, but just stick to the 2-part equation (even if you don't fully understand it), and it will all come out right in the end since the math doesn't lie. Please let me know if you need me to clarify anything!
IrishLass
