How to figure how much oil for mold.

[Sprag]

144 oz's divided by 16 = 9lbs

 

[Hazel]

And I am like you, I will use 70 oz of oil and any left over go into yogurt cups for sample soaps or guest soap.
We think alike. haha

Kathie

The excess does make nice guest soaps. Candy molds work great for tiny decorative soap.

Are you going to try another batch with 144 oz of oil?

 

[kmarvel]

I went to Summer Bee calc and put the 12 x 12 x 2.2" in for the oils and came up with 132 oz of oil and total soap before CP cure with 193.5 oz of soap. Which with the 132 oz of oil comes to an 8 lb mold. DANG!!!!!! I made a honkin' soap mold!!! hahaha

Live and learn!!! I quickly (fastest ever) lined a 3 lb mold and repoured my soap in that along with 4 yogurt cups. haha I think it will be ok.

Decided to make them 2.2" high instead of 2.5".

 

[Hazel]

At least you made your own soap mold. I wish I could make my own. Please post pics of this batch and let us know how it turned out.

 

[kmarvel]

Hazel, I will do that! This weekend it is back to making a "smaller" soap mold. 144 oz of oils sound like a lot to me!!

 

[LBussy]

Hey all ... sorry for bumping this thread but I thought I would share:

[Link no longer functional. Removed by SMF Modmin Team]

This is a spreadsheet that will allow you to figure mold volume in ounces or grams, in rectangular or round molds, with 0.40 or 0.38 factors. For round use the green boxes (H & D), for rectangular fill in L, W and H. If you have any number (including 0) in the D (Diameter) box it will figure the volume of a round container based on that and the height, so be sure to delete that field if you intend to figure rectangular.

I'll try to remember to leave this up and available, but it's on my working DropBox account and could be deleted or moved so snag it now if you want it.

 

[Hazel]

Lee -

Thanks for sharing! I downloaded it to DB and played with it. My results were just one ounce off (small mold) to 3 ounces off for the 5 lb mold. It could be because I didn't double check the width or it could be because I discount water and have room for more oils. Anyway, it's very helpful and it's generous of you to share the calculator.

 

[LBussy]

Happy to help. I can't speak to why these are right, just that *if* the whole 0.40 and 0.38 factors are correct then these are correct.

 

[Bubli]

Stupid question....I am reading conflicting opinions on how to calculate and what the results mean. After reading a few different sites, as best I could gather, when you multiply L X W X D X .40 you get the amount of oils AND water that mold will hold,right? Or do you have to add your water amount to this total. I am about to order new molds and wanted as perfect a fit as possible, I found some people that make custom. So is it just the oils or water too? The .40 represents water right?

 

[LBussy]

Not a stupid question Bubli, was wondering the same thing. I just took a factor that someone else posted and made a spreadsheet.

 

[scotsman]

I may be wrong here, and this may have already been said in an earlier post, but from looking at the formula and comparing it to various base recipes I have, it would seem that the .40 is actually the water % in the recipe, or rather, an approximate. This would explain why it doesn't come out quite right for some. If you use a water % other than 40 then the formula will be off a little bit. So, if I'm correct, and I may not be as math is not my forte, the formula should be as follows:

Length x Width x Depth = Volume

Volume x Water % = Total oil weight for mold

By way of example lets say the interior dimensions of the mold are:

Length=24"/Width=3"/Depth=2"
So...
24 x 3 x 2 = 144 cubic inches volume

If we're using a water % of 40 then:
144 x .40 = 57.6 oz of oils

But now let's say it's your first time making soap and first time using soapcalc so you opt to go with the default 38% water. Your equation is 144 x .38 = 54.72 oz of oils

So that 2% variance in water gives us a variance in total oils of 2.88 oz. not that big of a difference, but let's say you use 33% water for your recipe. Now your equation is:
144 x .33 = 47.52 oz of oils

That gives you a variance of 10.08 oz of oils. This is a significant difference. If you make your recipe with 33% water, but calculate using the standard .40, then you will still have a considerable amount of room left in your mold after you put the batter in it. And this doesn't even account for coloring, fragrance, or additives...though these are usually a much smaller % in most recipes.

The initial formula with the standard figure of .40 is solid, and will get darn close for most people, but if your recipe calls for a rather steep water discount then you would benefit from recalculating and swapping out the standard .40 for whatever your water % happens to be. 38% water would be .38, 33% water would be .33, etc.

Again, this is just a theory and I may be way off base with this one. Maybe at some point if I have some spare time and supplies I will do an actual test of this theory and post my findings here. I'm actually rather curious to know for sure. I hope this is helpful.

 

[coffeetime]

Scotsman, if the water amount used is going down from 40% to 33% in your example, wouldn't that mean you need more oils to fill the same volume mold, not less? With less water used, you would want to increase how much batter you are making by the missing water or your mold will be short.

I usually water discount by varying amounts depending on the recipe, and I found I couldn't use that formula at all. I had to trial and error it with that formula as a starting point. Took a couple of batches but not a big deal.

 

[scotsman]

@coffeetime- you're right. I just reread my post. That's what I meant to write. I haven't really slept much the past couple days and got it jumbled around, lol! I guess I should try to go to bed

 

[LBussy]

The formula looks up the value in the header, so once you find out what factor works for you, you can change your personal copy of the spreadsheet and it will work as you intend.

 

[scotsman]

I want to try out that spreadsheet but unfortunately can't do it from my phone. My laptop took a header off the table and it destroyed the screen.

 

[Hazel]

Well, I'm not a math genius but I didn't think I was this bad at math. I went by the amount I calculated for a 5 lb mold and I still ended up with extra soap. It's not a big deal since I like to have extra to make small soaps in individual molds. But I still don't know why my amount is so off. According to the calculator, the mold 18 x 3.5 x 2.5 = 157.5 x .4 = 63 oz. (I should mention this is a new mold. I usually make 2 lb to 2.5 lb batches. I also don't generally fill the mold all the way to the top so I calculated slightly less which is why my original amount was a few ounces off.) Anyway, I decided to go with the calculated amount based upon the formula of 63 oz + 1 extra oz so I'd have the large loaf and a little extra for one individual soap. Since I used 33% lye concentration, I expected the loaf to be slightly under 2.5" but I was able to fill to the top and ended up 14.7 oz extra soap. Of course, the leftover soap's weight would include water, lye and additives. Still, this is an excessive amount to have left.

If I calculate using .33, it comes out to 52 oz (rounded off). This actually seems to be a more accurate amount for this size mold. I'm going to try another batch this weekend and use 54 oz to see how full I can get the mold plus possibly have a little left. I'll have to report back after I make it.

 

[LBussy]

You can change this number to adjust for the multiplier that works for you and your process.

Again I was taking for granted that these numbers were correct so if the collective finds out that they are not they can easily be edited. I have two spots there so you can say "I know somewhere between X and Y works for me" and show that range.

 

[Hazel]

Thank you! I didn't even think of changing it. I decided to double check the size of the mold because I had been using the sizes shown on the site. I thought maybe the mold is slightly smaller than was shown in the description. Nope...measurements were correct.

I'm learning something new. I'd never worried about calculating according to the formula since the small molds I used I had already learned how many ounces of oil I needed. So, I never double checked them based on this formula.

 

[scotsman]

I tried the formula with my small loaf mold that I use for test batches but changed the .40 to .38 because my water is 38% and it filled the mold almost perfectly. I'm going to try another batch using 33% water and use .33 as the multiplier to see if it works. Will post up the results after the test. Keeping my fingers crossed.

 

[LBussy]

Okay I did some more work. The "factors" provided were a pretty close rule of thumb but as folks have noticed not always right. I have done a new spreadsheet that should be much closer AND allows one to tailor the water%.

Here's the spreadsheet - as always please download if you want to keep it because it's possible I move something and break the link at some point.

I don't know how everyone figures water but this assumes water as a % of oil weight as shown on SoapCalc. It also assumes the oil you use weighs 0.033 lb/in^3. "Solid" oils like Lard, Tallow and Shortening weigh 0.031 lb/in^3 but I *think* that's as a solid so using the oil number only should get you very close.

[Link no longer functional. Removed by SMF Modmin Team]

As always, please let me know if you see a glaring mistake.