# Quantifying Pour Foam

Discussion in 'Molding and Casting' started by Leonard "Tazman" Qualls, Jul 29, 2022.

1. ### Leonard "Tazman" QuallsActive Member

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Need a little guidance from any of you who have worked with pour foam.

Problem- I am having a little trouble figuring out how much pour foam to use to fill 8qts of volume.

Current situation- I have made a fiberglass mold of a clay form, and now I want to duplicate it with pour foam. I'm using 5lb pour foam...the form is 8qt in volume, measured accurately. Anyone know where I can get an equation or formula for how many floz of 5lb pour foam to fill 8qt vol and still be at 5lb density? I'm trying to eliminate waste and be more cost effective than doing the ol' "start at one amount, pour it, and demold...then add a little more, and go from there"...that is a total waste of very expensive material and time. Been there and done that.

2. ### PsutaxiMember

My calculations show 23.5 ounces of foam ,foam goes by volume not by weight . This is going by 5 pound foam . Make sure you're at a good temperature and humidity . Best is 80 degrees I believe for the best expansion . But as always you have to say "but I don't know " in case something wrong lol. Split that in half for A and B

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3. ### Leonard "Tazman" QuallsActive Member

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Appreciate you doing the math and giving me the total. What equation did you use, or how did you come about that sum? Would like to know the equation so that way I can figure any others that I do based on volume

4. ### Frank E. Kotulamaster, judge, instructor

Smooth on I think has a calculator on how to figure it out

5. ### msestakWell-Known Member

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any of the old timers here remember an article in breakthrough YEARS ago about a fellow taxidermist that used a large quantity of pour foam to try and lift part of his sunken driveway ?

from what i remember it lifted more than the sunken part and cost thousands to fix

6. ### Leonard "Tazman" QuallsActive Member

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A long time ago when I lived in South Florida, I heard of a guy who mixed a rather large batch of pour foam and poured it into the bilge area of his boat to give it more floatation...next thing ya know, the stuff went off so big that it crushed his aluminum gas tank and buried his batteries and wires and everything it touched!
If you don't have some release agent, this stuff bites to whatever it touches. His boat was a total hot mess when it stopped growing. LOL

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7. ### Leonard "Tazman" QuallsActive Member

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Thanks. I checked it out. Their calculator is for basic shapes, so it doesn't do exactly what I need it to.
I was able to get the volume of the inside of the mother mold on each of the half dozen things I am creating, and they are all odd figures like - .254cu' (7.608qt) and .176cu' (5.283qt) etc.. I just wanted to know what equation the @Psutaxi used to get his sum.
For instance, if the volume of the above mold is 7.068qt, how much of part A and part B of 5lb foam to expand (10 times its size from liquid to cured foam) to fill 7.068qt of volume and remain 5lb density?
I think I'm going to call Smooth-on and see what they offer. Thanks for the guidance Mr. Frank

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8. ### tazzymotoWell-Known Member

I think the 5lb is per cubic ft. I would weigh out 2 1/2 lbs of each, should get you close

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