2 part urethane foam question

[Bill Motzer]

 Im getting ready to do some rock and base work with the 2 part urethane foam and it will be my first time using it. I could just go into the shop and see how much expansion I get with 2 small equal parts mixed as a test but I figured id see if I could get an answer without making a mess...
If I mixed 2 equal ounces of part A and B how much will it expand? I just dont want to mix a small amount and pour it in my mold and have it foam over and waste it.
Ive read that some foam will expand 3 times its liquid volume and some as much as 30 times its liquid volume. This foam im using is from McKenzie's.Thanks for any replies and tips.................Bill

[Old Fart]

I usually figure about 5 to 7 times expansion. The big problem is, temperature and humidity will influence the volume change, too.  No matter how much you try to plan with foam.....it will either be TOO MUCH or NOT QUITE enough.

[newbirdman]

Bill , I agree with Old fart . Mine usually expands aboyt 7 X . Just mix your 1 or 2 oz's and pour it on. You can always add more and in fact , it looks better when you let one batch expand add then add extra one of two .  Rick

[jermh1]

some of the 2.5 lb density stuff I have been using expands quite a bit more, after a 6oz pour the residue left in the cup will expand over 6 oz maybe 20x to 30x expansion. moral of the story is expansion is a function of density,  and yes temp is a big factor along with how well you mix it, use a drill with a bent wire ore a plastic spoon or fork, I have never had any humidity issues, but that is just here. There will always be a little too much or not enough just as Old Fart posted

[Laurier]

free rise approx 25 times it's volume , add 2 or 3 drops of water to the foam , and it will expand even more , use this method only for scenberies never for manikins.

[George Roof]

LMAO @ OF.  Ain't that the truth.  And I can't figure out which one upsets me more, ending up with too much or not having quite enough.  I don' t think I've EVER gotten it right.