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I'm OFFICIALLY lost.


Sponiebr
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OK, so I've finally hit the wall on understanding the whatforthisbe's of soapcalc.net. 

SO... In soapcalc I've started using the % of lye to figure out my correct volume of lye solution for my batches because I'm masterbatching my lye solution... 

No sweat... UNTIL I hit this little snag: I was double checking my amounts and here's the part I don't understand. I want a 40% lye to water solution. Let's take the following as an example:
For 1000g of water 400g of lye would be mathematically 40%.  Let's double check that: 1000*.4= 400. Right? 

WRONG! 
Soapcalc sez I need 666.66g of lye for that solution to be 40%. 

I'm sorry soapcalc but that's 66% and NOT 40%... Ok, so maybe it's like .666 (such an appropriate number for this example) - 1.00= .334... only .334 is 33% and NOT 40%. 

I've checked this across various other formulations and it sticks perfectly. They're ALL listed as 40% lye solutions but are actually 66% solutions... 

So... I checked against perhaps it's total lye solution to oils... NOPE! Turns out to be 34%...

WTAF is going ON here? I mean I don't really question the idea because it's been working PERFECTLY but I don't understand HOW or WHY they're listing it as 40%. The actual lye to water ratio is listed as 1.5:1 which is spot on... 

Anyone?   

Cheers, 

Sponiebr
The Executor of Bad Ideas, Sundry Services, and Mathematical Conundrums.  

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This is that weird math that you need to use the values from the whole solution, not one variable against the other.

 

Let's say the oils in my batch require 100 grams of lye. The calculation for 40% "solution" is the lye x 1.5 or 150 g H2O.

The total solution is 250 grams, of which 100 (40%) is the lye: 100/250 = 40%

the revers of 250 total solution * 0.4 = 100 grams of lye

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1 hour ago, TallTayl said:

This is that weird math that you need to use the values from the whole solution, not one variable against the other.

 

Let's say the oils in my batch require 100 grams of lye. The calculation for 40% "solution" is the lye x 1.5 or 150 g H2O.

The total solution is 250 grams, of which 100 (40%) is the lye: 100/250 = 40%

the revers of 250 total solution * 0.4 = 100 grams of lye

Ok I have 3785g of water I will divide that by 1.5 to get 2523g for my lye 3785+2523=6308  2523/6308=.399999999999999999 (call it 40%).... 

Thank you! 

 

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