Calculating recipe with unknown KOH%

[tyerod]

I recently decided to give shave soap a try. I ordered some KOH as well as other items from WSP. I then tried to find the % purity of their KOH. The MSDS they offer indicates it is 90-95%. Questions asked about this just reiterate this information and I was directed to their soap calculator, a licensed version of SoapCal, with has the percent already set up. When I asked what the default % for KOH was set at it was indicated it was set by the vendor and they do not have that information.

My question is when calculating the amount of KOH needed should I just assume 90% and super fat for any additional or maybe split the difference and go with 92.5%?

 

[DeeAnna]

The WSP version of soapcalc is set up for 100% KOH purity according to the check I did today. That's likely to cause separation problems if you use this calc but make liquid soap with KOH that is decidedly less pure than 100%.

If you're guessing, I wouldn't get overly fancy about tweaking the superfat. In that case, I personally would use the real soapcalc and choose 90% purity, or I would use Soapee.com and enter a best guess. Set the superfat to 3% or less and go with the recipe.

Or test your KOH and use soapee with the actual purity you find -- see http://classicbells.com/soap/purityCheck.html

 

[tyerod]

Thank you for that link. I have been wanting a way of checking purity without a bunch of burets and reagents. My mad scientist side might just start doing this for all of my lye usage

 

[DeeAnna]

It's not a super accurate method. But it's good enough for soaping.