Ingredient purity standards?

[Aloicious]

Hey y'all, so I'm just starting with soap making and while I'm putting together a shopping list I was wondering about the purity standards of the hydroxides (KOH/NaOH) that y'all use.

I have a fairly strong chemistry background (though nothing specific to soap making). and while I'm shopping around I've noticed a variety of purity ratings, specifically on KOH more so than NaOH, ranging from ~90% up through 99+%. In my experience in the lab, a variance of ~10% purity is HUGE and can make or break the entire reaction. I doubt its that severe with soap, but does the purity standards between a 90% pure KOH and 99% make a difference in the end product with soaps?

Most likely I'll end up spending the extra to get 99+% since my OCD will kick in with that kind of thing, but just wondering what y'all have experienced with it.

 

[The Efficacious Gentleman]

If you know you are getting 90% or the (almost) pure stuff then you can adjust soap calc accordingly so it doesn't actually make that much of a difference to your soaps.

 

[MarisaJensen]

I'm not a chemist but most soap suppliers carry good lye. I've used Essential Depot's Lye mainly because I can pick it up within 2 hours. I've never had a problem with their lye quality. I'm not a chemist but I'm interested in what others have to say about this. Now, I'm off to see if I can find the specs on my lye.

 

[MarisaJensen]

Just looked at ED's Lye. They are 99% and affordable (depending on where you live). Shipping is what always gets me with some things.

 

[Aloicious]

If you know you are getting 90% or the (almost) pure stuff then you can adjust soap calc accordingly so it doesn't actually make that much of a difference to your soaps.

yeah I suspect that as long as the lye percentage is calculated to be the limiting reagent in the reaction that would be the most important factor.

 

[new12soap]

As you said, the 99% KOH is a lot more expensive, and the problem is that it is so hygroscopic every time you open it the purity changes.

Purity of KOH used to be a problem, so most people that used it (primarily for liquid soaps) had to calculate a heavy lye excess, then neutralize. Now there are several good lye calculators that account for the 90% purity, so a lye excess is no longer necessary.

AFAIK, most soapers use the 90% with very good results. Just know your calculator of choice.

 

[Susie]

^Exactly what new12soap said! I buy the ED KOH and NaOH, but I live in a humid climate, so every time I open it, the weight(and therefore purity) changes. I just use the 90% purity on the lye calculators, and it works out fine.

 

[cmzaha]

Since you are a chemist, maybe you know of a chem house in your area. I purchase mine from Gallade Chemical and have never had any problems. I am thinking my last coa sheet stated it at 99% pure. It is so much cheaper if you can bypass shipping costs.