Oil weight vs Water % Help please

[BlowinBubbles]

I'm trying to work out the difference in oil required for batches based on their water %. As the water % falls, I need more oils to maintain the same volume of soap (and re-run the recipe through a calculator).
I work in metric on the understanding that I take the LxWxHx.7 to give me 'full water' for my oils but what if I'm only wanting to use 30% or 20% water?

 

[mx5inpenn]

Run it with full water and see what the total amount before cure is. Then you can play with the oil amounts at the water % you want to use til it matches the total again.

 

[BlowinBubbles]

Going by my calcs, my mold would need 1139g of oil at full water (40%) and would result in a loaf weighing 1741g.
On mx6inpenn's advice, In SoapCalc, I dropped my water to 20% and upped my oils to 1300g to acheive the same(ish) loaf weight (14g lighter).
I now have 5 gingerbread men surplus to my loaf! Cute, but I can't afford to make that much extra but I can't keep making batch after batch until I hit the right size.
Mold is 31x5.9x8.9 (cm)
Recipe is 100% OO(1300g) with 5% SF
water 260g
NaoH 158g
KoH 11.7g

No fragrance.
Off now to buy more oil....

 

[mx5inpenn]

Sorry that didn't work out for you! None of the calculations for molds are exact since different oils have different volumes at the same weight. How much do the gingerbread molds hold? That should give you an idea of what to reduce the amounts to.

 

[BrewerGeorge]

You don't need to do more experiments, you have enough info for this recipe now to calculate much more precisely than the general rules of thumb.

Weigh the soap men as soon as you can (to minimize lost water). Subtract that amount from the previous total loaf weight. Now put your recipe into soap calc and select the % radio button in section 6 to lock the oil ratios. Next lower the amount in the green box in section 2 until the new total soap weight before cure matches the new goal (original weight minus overage weight). You'll probably have to take several tries at it, but that's as easy as changing section 2, recalculating and viewing the result again.

After that, if it were me, I'd switch section 6 radio button to grams and round them all to the nearest whole number before a final recalculation for the finished recipe. Just makes things cleaner.

This will work as long as you keep the same mix of oils and water percentage.