# How to figure how much oil for mold.

Discussion in 'Lye-Based Soap Forum' started by Soapmaker Man, Mar 26, 2008.

1. Sep 2, 2008

### eargirly

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I like to know the reasons behind things to. Is it because the amt of oils used in the process equals 40% of the total volume of the final outcome? That would be the only reason I can figure for the .40 there.

Hope someone can help me on that. I haven't done this stuff yet, so I am a complete noob. But, first batch is coming soon and I want to be sure I have all this right. I studies and studied the RTCP method last night and lye calculators this morning.

Thanks for any help!~
ear

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2. Oct 9, 2008

### lindar

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great information to no would have liked to have seen this a few months ago

3. Oct 14, 2008

### Bigmoose

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Hello everyone,

I make my own molds and use a volume calculater at the site below.

Hope this helps everyone as much as it has helped me.

Bruce

[Edited by SMF Modmin Team to remove non-functioning link]

4. Oct 17, 2008

### ballininthamix

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I think it is important to note that the formula Paul provided gives you the total weight in ounces of oil by multiplying the total volume in cubic inches by .40. This doesn't necessarily mean that the oils make up 40% of the volume. So this formula will work as long as you can compute the volume of your mold in cubic inches.

Now let's say you have an odd shaped mold or want to measure the volume in fluid ounces. You can still use this method, just make sure you convert your liquid ounces to cubic inches.

There are approximately .554 fluid ounces in a cubic inch. So multiply your total fluid ounces by .554 and multiply that by .40 and you've got your total weight of oil. Like this:

TOTAL (fl oz.) x .554 x .40 = TOTAL OIL (oz.)

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5. Nov 3, 2008

### eargirly

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thanks for that info bigmoose and ballin! That helps me a great deal as well! I am having my father (a woodworker) make some molds for me and that is great info, indeed. Everyone here is so helpful. Thank you over and over again!

~ear

6. Dec 17, 2008

### welder

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Good point Ballin.

Until you mentioned that, like Eargirly, I had also mistakenly thought that 0.40 was the volume of oil required (as in 40% of total volume)

Okay, so once I know my mold volume and do the math to get the oil weight in ounces, how do I calculate how much water I need?

I know that after I calculate my oil requirement (in ounces), I simply run that figure through a lye calculator to find the lye measure required, but I still don't know how to get the water measure required.

Help!!!!!

7. Feb 19, 2009

### donnux

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Calculating mold size

I just set up a bunch of soap making URLs and was looking for an answer to exactly this question. So I came to The Soap Making Forum site and found that it is the second question!

I arrived at this 0.4 number a different way, that is by measuring several bars of soap, then averaging their weights. Some simple arithmetic worked out to 0.4 ounces per cubic inch of soap, the same number you have come up with. So now I can consider that I did some math right, for a change!

Thanks for verifying this for me, now I can proceed with more confidence that my goop will fit into the mold without overflowing.

8. Apr 17, 2009

### maheka

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Anyone would like to convert this to the metric system? My math isn't enough...

9. May 1, 2009

### Godiva

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I homeschool my son, who is in 8th grade, and had to learn the formulas for volume. I LOVED math in school, was my favorite subject. Science was my second favorite. Then English. Did not like history much. My hubby hated math. Luckily all my kids inherited my propensity for math and have done well. My 3 oldest have told me that other kids in their class would seek them out for help.

Now that I'm going thru American History with my son, I find I enjoy it more this time around.

10. May 1, 2009

### JulieJ

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What about the lye/water solution? Don't you have to figure that addition to the volume of the mold? Thanks@

11. May 1, 2009

### Godiva

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I use a soap calculator and it will calculate how much water/lye to use. I've been using Paul's formula for all the different boxes I've been using, and it has worked out perfectly.

So (L x W x H) x .40 = amount of oils. If it's 3 lbs (48 oz), you enter the percentage of each oil, hit compute, and it will tell you how much water and lye you need for your recipe.

12. May 1, 2009

### JulieJ

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Oops, I guess I didn't make my question clear, sorry. What I meant to ask is if you have to figure in the lye/water solution into the volume. For example... if your mold holds 16 ounces and your recipe calls for 16 ounces of oils, PLUS 6 ounces of water/lye solution, wouldn't you need a mold that holds 22 ounces? Thank you.

13. May 2, 2009

### Godiva

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I suppose so. If I am using a recipe that uses ounces instead of percentage of the oils, I will add up the oils and then figure out what percentage each oil is in the recipe, and apply those percentages to however many ounces I need for my mold. I've not worked the other way around.

14. May 12, 2009

### Val

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Hi

I found this and It helped me on the mold size and how much. You just enter the measurements of your mold and it give you how much oils to use.

Hope this helps,

Val

[Edited by SMF Modmin Team to remove non-functioning link]

15. May 16, 2009

### xraygrl

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I just made new molds today (with DH's help....he would NOT let me play with the saw :evil: ) so I needed this. TFS!

16. May 20, 2009

### topcat

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I tried using this formula to calculate in grams oils weight and it does not compute :wink:

I found this link online which give the metric calculation for those of us who use grams. I am just about to make a batch in a new mould using this calc so I will edit my post and let you know how successful it is.

Tanya

Edited to add: Yes - this metric calculation definitely worked for my new mould. Excellent!

[Edited by SMF Modmin Team to remove non-functioning link]

17. May 25, 2009

### chrisnkelley

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Thanks for the formula! Seems pretty simple! So, by oil, you mean the combo of bases you are using, right? (I'm new, sorry!) Like olive oil, castor oil, etc?

18. May 25, 2009

### topcat

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Yes, oil weight is the total weight of all the oils you plan to use in your recipe. HTH!

Tanya

19. May 25, 2009

### chrisnkelley

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Thanks! It doesn't include weight of essential oils or additives though, right?

20. Jul 30, 2009

### Christianbeauty

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This is way too helpfu--i have been racking my brain for days trying to figure it out and I figure I would just pour all my oils in the mold and divide it in half to see if it works--but doing this formula is way too helpful---i am going to try it in my new mold and thanks!!

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