# Soap Mold Volume Question



## SoapSap (Dec 2, 2014)

I often calculate the wrong amount of soap batter for my loaf molds. If I am filling a 3 pound mold should I be using 3 pounds of oil, and not be accounting for the water weight? Or do I account for the oil weight plus the water weight?  

I do measure my molds using the math formulas I have read about. However, I am never sure if this formulates for total batter weight or just the oil weight. 

How do others do this?  I have found that what I purchased as a 3 lb mold may not be exactly that. So I do calculate the volume mathematically.


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## Susie (Dec 2, 2014)

A 3 lb soap mold will hold 3 lb soap batter.  I use the "1.5 times the oil weight rule of thumb" to get the soap batter weight if my calculator does not already show it.  It is not perfect, but is close enough to avoid having to scramble for more molds.


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## dixiedragon (Dec 2, 2014)

Do you have the volume for the mold? Your soap will be roughly 2/3 oil and 1/3 water. 

My mold holds 50 ounces. I make a 2 lb batch of soap - that's 32 ounces. 32 ounces of oil + 16 ounces of water = 48 ounces.

Volume ounces and weight ounces are not interchangable as far as calculating lye, etc, but they're close enough for calculating volume.


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## new12soap (Dec 2, 2014)

SoapSap said:


> I do measure my molds using the math formulas I have read about. However, I am never sure if this formulates for total batter weight or just the oil weight.




The formula of length x width x height x .40 = total oils


I dislike how molds are rated for 3lbs or 5lbs because those are totol batch size and I never refer to my batches by total size but by oils. To me, a 2lb batch is 2lb of oils. So I just use the above formula and it works out pretty well.


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## The Efficacious Gentleman (Dec 2, 2014)

There is a sticky in the cp section that deals with mould calculations - well worth a look for some great tips


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## IrishLass (Dec 2, 2014)

I use the same calculation as new12soap. Works out pretty well for me, too. Here's something to keep in mind, though- depending on the water amount you decide to use in whatever given batch you make, you may end up having slightly more or less batter than you had calculated to fit your mold perfectly, but you can easily adjust things for next time. Just take notes.

 IrishLass


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## DWinMadison (Dec 2, 2014)

new12soap said:


> The formula of length x width x height x .40 = total oils
> 
> 
> I dislike how molds are rated for 3lbs or 5lbs because those are totol batch size and I never refer to my batches by total size but by oils. To me, a 2lb batch is 2lb of oils. So I just use the above formula and it works out pretty well.



This method works great for me.  Also, for the record, the 40% of volume works for round or columnar molds too.  The calculation is

Radius (not diameter) of the container squared  x Pi x Height x .40

so for a 3" PVC pipe that is 12" tall:

1.5 x 1.5 x 3.14 x 12 x .40 = 33 ounces of total oil.  

You would then run this through your calculator to get your lye and water measurements.


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