A math question..

[samirish]

So, I am going to try my hand at making soap in a round silicon cake pan. I read one of the stickied posts here regarding how to figure out how much oil you will need for your particular soap mold. That thread has 12 pages of replies! Oh geeze....

So I started reading and some people supplied links to different calculators, however I think those posts are old as none of the links worked. Then volume vs weight vs mass started to be discussed and at that point I was just lost.

I have no idea. Could someone pls help me. My cake pan is a 9 inch round that is 1.5inches deep.

Thank you!

 

[seven]

when i did my soap cake i just put water inside the mold and place it on the scale. then minus the number with the weight of the mold itself. bear in mind, that the final number you have is the total weight of the soap (lye + water included).

and yes, water and oil have different consistencies, but you get the rough idea. give or take slightly, you won't miss much.

sorry i can't help more with the proper calculation. i suck at math.

 

[judymoody]

Fill your pan with water. Weigh the water. That's roughly the amount of your total recipe. Oils are about 2/3 of the recipe weight, more or less. Hope this helps!

 

[samirish]

Thanks so much. Those answers are pretty much what Ive been looking for. Simple and to the point.

Thank you

 

[songwind]

From the thread referenced:

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

Not helpful with a round mold/pan, right? Or is it? LxWxH is volume, and we can get the volume of a cylinder.

pi*r^2 is the area the circular bottom covers. pi*4.5*4.5 = 63.61 sq. in.

Area x Height = Volume, so 63.61 * 1.5 = 95.42 cu. in.

95.42 * .4 = 38.xx oz of oil.

With the "weigh it full of water" approach we get:

95.42cu. in * .55oz/cu. in = 52.48oz total.
52.48 * (2/3) = 35oz of oil, give or take.

So, it's not exactly right, but it won't overflow, which is perhaps just as good.

 

[Seawolfe]

Aaaagh I HATE those volumetric calculations!!!
{pant pant}

Pour water into the mold to the height you wish your soap to be. Get the weight of that water. If you use soap Calcs default 38% water then the rest will be oils - lets call it 60% to compensate for the lye.

TADAAA!!

This actually is a little short (which is ok for safety sake) and 66% or 2/3 might be more accurate, but hey, heck of a lot easier than finding the ruler, measuring in 1/16ths of an inch, trying to remember what pi is .....

 

[Wellingtonchase]

You rock Eric thank you.

 

[samirish]

Thank you all for the helpful replies.

 

[saurian]

Can I just add - have a second mould handy just in case, a little cheap silicon muffin mouild can save the day if you do make too !much.

 

[Susie]

Can I just add - have a second mould handy just in case, a little cheap silicon muffin mouild can save the day if you do make too !much.

I learned the hard way to keep a small mold of some sort right by where I am soaping. You just never know when you are going to have a couple of ounces that need to go somewhere. I have a silicone mold that makes 1.5 oz bars, or I have used a Rubbermaid food storage container(that the lid got melted, so not used for food any longer). It has a 5 on the bottom in the triangle.

 

[kyliecoast]

Will 100ml of oil weigh 100gm? I believe 100ml of water weights 100gm.

 

[The Efficacious Gentleman]

Different oils have a different weight/volume ratio. Olive oil, for example, is about 900 grams per litre.................

 

[Dennis]

Roughly, but oil is lighter than water. Some would say close enough. However, it depends on density and if you wish to be exact the answer is a resounding no. Here's an example robbed from the internet using my growing copy and paste skills. It is always amazing to me how much knowledge is available at our finger tips.

Density of olive oil is about 0.918 g/ cubic cm at 15 degrees Celsius.
D=M/V
0.918=M/100ml
Mass should be 91.8g

For me as a rule of thumber, close enough to say yes.