Calculated mold volume but it made too much

[ewhitake]

Calculated what I thought was total volume for a new mold using the following formula. Measured in cm's:
8x5.5x7
Took the total and multiplied by .40 and turned that total into grams. I ended up with too much soap.

What went wrong?

 

[justsomeguy]

It's usually measure in inches, run through the formula, weight in ounces. Excellent write-up about it by @DeeAnna, here

 

[dmcgee5034]

Additives? Could be those, if you use them.

 

[artemis]

Did you use the result as your oil weight or as your total batch weight?

 

[ewhitake]

Did you use the result as your oil weight or as your total batch weight?

Total batch weight. But I think I have it figured out. I don't work in ounces. Grams are easier for me when weighing but inches are easier when measuring. I watched a Youtube video made by an Australian and she measures in cm. I mixed up inches and cm while measuring so my numbers are all wrong.
Also length x width x depth x .4 doesn't work in cm. I found something on this forum about multiplying cm measurements by .7. I thinks this will work out better.

 

[Ekuzo]

You can also measure the weight of water the mold can hold and use it as total batch weight in your calculations. You'll end up with just a little bit of extra batter which you can fine-tune with your next batch

 

[DeeAnna]

If measuring in centimeters, the scaling factor is.0.7, not 0.4. And the answer is grams, not ounces. Link to more info is in JustSomeGuy's post, see above.

 

[ewhitake]

You can also measure the weight of water the mold can hold and use it as total batch weight in your calculations. You'll end up with just a little bit of extra batter which you can fine-tune with your next batch

You know, I originally tried this for cavity molds. Poured water in one while it's on the scale and multipy by the number of cavities. Didn't work very well. Always ended up with way too much :-(

 

[ewhitake]

If measuring in centimeters, the scaling factor is.0.7, not 0.4. And the answer is grams, not ounces. Link to more info is in JustSomeGuy's post, see above.

Yep - this does work better. Still ended up with a little too much but I'll just adjust my measurement numbers down a bit and it should work

 

[KimLynn]

You know, I originally tried this for cavity molds. Poured water in one while it's on the scale and multipy by the number of cavities. Didn't work very well. Always ended up with way too much :-(

That’s been my experience, too. Soap batter is heavier than water, so it’s not a very precise measurement.

 

[Ekuzo]

That’s been my experience, too. Soap batter is heavier than water, so it’s not a very precise measurement.

Actually, soap batter usually has a lower density than water - that's why the same weight of oil/lye at emulsion gives you more volume if measured with water - and you end up with extra batter. But I understand why this method doesn't work well for everyone, it gives you perfect result only the second time if you don't adjust additionally the first one

 

[FrayGrants]

I always just take the volume of the soap mold and divide by 1.37 to get the oil weight, i.e. standard loaf mold is 40 ounces so you need 29 ounces of oil. You can determine the volume by weighing water or looking up the capacity of your molds. Works perfect for me every time.