How to figure how much oil for mold.

[JazzKitten]

hey paul, thanks for the helpful thread!!..


just curious, where does the .40 come from??

It will be to do with the density of oil. For instance, 1 cubic metre of water weighs one tonne, 1 litre of water weighs one kilogramme. So the volume calculation that Paul has given has the volume of the mould multiplied by 0.4 because I oil is heavier than water - also it's given in inches so that constant of 0.4 will account for the weight conversion to ounces.

 

[earlene]

One caveat: In spite of this standardized conversion formula for determining how much oil to use when making soap batter to fit into a specific mold, it does not take into account any variables for lye concentration, which can alter the amount of water (or water replacement), which in turn will alter the total batch weight (and density or volume) of your raw soap. Nor does it take into account additional additives and their density, as when one adds pumice or salt, etc. to the batter. All these sorts of things will alter the final total density of your soap and it may be a greater or lesser volume than will fit your mold to the particular depth you thought it would, remembering that neither volume nor density are the same thing as weight.

And there is one other factor that alters density of a substance, and that is heat. Heat causes many substances to expand, including soap, so the same recipe may produce a larger volume when hot than when cold.

Not to burst anyone's bubble about a tried-&-true formula for determining how much oil to use when altering a soap formula to fit a particular mold. But as many a soaper has discovered, sometimes the formula doesn't always produce the amount of batter we thought would fit the mold perfectly and sometimes it falls short, while other times we need a back-up mold to put the extra batter into, such as an individual mold or two.

 

[stephswan]

Hi all, a little late to the game, and I probably should just start a new thread, but I found the formulas in this thread helpful, so just want to double check I'm doing the math correctly for my individual silicone molds:

I have a cloud mold (12 in total), so i poured water in 1 and got: 2.2 fl oz.
2.2 FL oz x 12 (number of molds) = 26.4 fl. oz
Then 26.4 x .554 (to transfer into cub in) = 14.63
14.63 x .4 (the magic number of calcing oils) = 5.85 oz of oil needed for this mold

this is math correct? just seems like such a small bit of oil.

 

[SoapDaddy70]

Hi all, a little late to the game, and I probably should just start a new thread, but I found the formulas in this thread helpful, so just want to double check I'm doing the math correctly for my individual silicone molds:

I have a cloud mold (12 in total), so i poured water in 1 and got: 2.2 fl oz.
2.2 FL oz x 12 (number of molds) = 26.4 fl. oz
Then 26.4 x .554 (to transfer into cub in) = 14.63
14.63 x .4 (the magic number of calcing oils) = 5.85 oz of oil needed for this mold

this is math correct? just seems like such a small bit of oil.

I do not think your second equation is correct. Once you get the total volume in fluid ounces you should be multiplying that number by 1.8 to get your cubic inches and then multiply by the .4. So it would be.
26.4 x 1.8 = 47.52 cubic inches
47.52 x .4 = 19 oz of oil needed

 

[stephswan]

I do not think your second equation is correct. Once you get the total volume in fluid ounces you should be multiplying that number by 1.8 to get your cubic inches and then multiply by the .4. So it would be.
26.4 x 1.8 = 47.52 cubic inches
47.52 x .4 = 19 oz of oil needed

THANK YOU!!! I was thinking the final oils looked way too light.

 

[AAShillito]

Thank you! This is super helpful!

 

[ameliashawn]

Multiply the number of fluid ounces of water by 1.8 to get the total cubic inches of the mold. For example, if your mold holds 12 ounces of water, 12 X 1.8 = 21.6 cubic inches. 21.6 cubic inches in the mold X 0.4 = 8.64 ounces of oils in that recipe.

 

[Spice]

Hi everyone.I wanted to post this as a sticky so all could learn how much oils are needed for your mold. Here is the way to figure it.

Lets use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.

You take length X width X height of pour, that number X .40. So;

12 X
3.5=
42

42X
2.5=
105

105X
.40=
42 ounces of oils needed for this mold.

Apply these same numbers for your mold size, weather a log, slab, or block.

Paul

is the .40 the %of lye?

 

[lshone]

is the .40 the %of lye?

No. The .40 is ratio of the weight of oil to cubic inches, for 1 cubic inch.

Multiply the volume of your mold, measured in cubic inches, by .40 to get the weight of oil required for your mold.

Keep in mind that the .40 is an approximation, so you will need to experiment with amount for your mold and receipe, and adjust up or down as required.