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  • Polyurethane foam troubleshooting help

    So, we've been using two-part, soft and rigid, urethane foams for a few years now- foaming heads and bodies etc.

    I've used foams from Reynolds Advanced (smoothon), Monster Makers, BITY and some off of ebay, but I seem to be getting a recurring problem with collapse after expansion with the flexible type.

    Needless to say- that makes for some funky feeling and expensive foam props.

    Specifically-

    I use 3 or 4 lb flexible foam to fill fairly large cavities (about 2-5 cubic feet).

    I am using proper/clean mold materials- silicone and fiberglass- and I am using the correct release- either liquid or spray form.

    The temperature of the work space and materials is always above the minimum and I use a scale to measure when required.

    I have hand mixed and jiffy mixed- both carefully and thoroughly- with similar results.

    The only time I do not have any issues is when I am mixing smaller amounts- like 2-6 oz.

    I have contacted all of them for help, but none of them have been able to solve the collapse issue- they just repeat the above list.

    What I THINK is happening may be related to the volume and how it reacts to a free-rise situation. I think as the foam expands to fill, it is in a free-rise state and the bubbles created are expanding beyond the materials ability to keep them trapped. The only solution to that- I THINK- would be to use more- a lot more material so that is reaches a back pressure situation before the air bubbles get to big.

    I've even given this idea to the tech support guys and it gets dismissed... Perhaps I AM insane...

    Anybody?
    How can a man die better than facing fearful odds, for the ashes of his fathers and the temple of his gods.

    What you put into your mind- you put into your life.


    www.zombietoxin.com

  • #2
    I have occasional collapse issues even on big props... i got a few funky looking full size gators. Two counts, and I am guessing the factors were, one was age of chemicals and the other was room temp. I think I also had one where it seemed like a gas pocket trap. But just guessing....

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    • #3
      I have found that when it gets to hot, it starts eating itself before it cures. Or it heats the release to much .
      Less hardner and a clear coat over the release and a cooler place seems to be the trick for me so far...

      Stew

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      • #4
        Im gonna be the odd man out and say your issue sounds like humidity. Do you have a hydrometer to measure humidity? Moisture in the air plays havoc with my foam. having a dehumidifyer in the shop helps greatly, I dont even run foam when the humidity is higher than 70% outside.
        Allen H
        www.Stiltbeaststudios.com
        http://www.youtube.com/user/Stiltbea...s?feature=mhee

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        • #5
          Another answer to your back pressure theory is to use sheet plastic and run the foam in layers, pushing down on the sheet plastic to create pressure. I have done that in the past with success.
          Allen H
          www.Stiltbeaststudios.com
          http://www.youtube.com/user/Stiltbea...s?feature=mhee

          Comment


          • #6
            Thanks for the help.

            Well, at first I was suspect of the age of the materials, but after having the same problem with numerous different batches I gave up on that theory for the most part. I hope thats not it- how would you be able to tell?!

            Then I was thinking about the release- maybe it was reacting, but I switched from 2831 to PVA and still got collapse. 2831 seems to be the way to go with urethane foam- I can get several pulls between coats.

            I'd love to try the plastic sheet/ back pressure idea, but I can't get my hands inside the mold cavity.

            As for the humidity- well I did ask the smoothon tech about it- but in regards to low not high. The very first pour we did was in the winter- warm but dry and got substantial collapse. Anyway he didn't give much input in regards to humidity, but I can definitely see how it may play a part. Damn... my workspace is NOT air conditioned and has a pretty large volume that is not well sealed. Dehumidifying it is going to be a biotch.

            I guess I could drag it into my office area...

            Thanks again everyone.

            -Rob
            How can a man die better than facing fearful odds, for the ashes of his fathers and the temple of his gods.

            What you put into your mind- you put into your life.


            www.zombietoxin.com

            Comment


            • #7
              Be careful working in a smaller space, most foams off gas syanide as they expand, so ventalation and all that. just covering our butts lol. good luck with it and keep us posted.
              www.Stiltbeaststudios.com
              http://www.youtube.com/user/Stiltbea...s?feature=mhee

              Comment


              • #8
                Well, thanks to the weather going bonkers and cooling down to the 60's (!) I can't say with 100% certainty that humidity was a factor, BUT I will say since I moved into a climate controlled area I have had zero collapse.

                To further confuse things I was also using a different foam... so... yeah...

                Anyway, my experience has led me to believe that BITY foams are somehow better. They're probably all the same, but somehow I get less collapse (if it happens) and much better expansion.

                So far, for making body forms, their 3lb flexible has worked the best.

                Another thing I think is important in the learning curve is to give up on trying to cut the amounts used to absolute minimums to save a buck or ten. It seems better to overfill slightly- just make sure your molds are strong enough to handle back pressure.

                Thanks everyone.

                Attack mannequins are now part of our doll attic.....

                Here's a few of the dozen we made.
                Attached Files
                How can a man die better than facing fearful odds, for the ashes of his fathers and the temple of his gods.

                What you put into your mind- you put into your life.


                www.zombietoxin.com

                Comment


                • #9
                  Please tell me your wearing a vapor regulator?
                  sigpic
                  PEACE, ADAM
                  www.poisonprops.com

                  Comment


                  • #10
                    Yup, sure do. I'm curious- since you're here- what your opinion about foaming is. Would appreciate the pro advice!
                    How can a man die better than facing fearful odds, for the ashes of his fathers and the temple of his gods.

                    What you put into your mind- you put into your life.


                    www.zombietoxin.com

                    Comment


                    • #11
                      I live in california about 14 blocks from the beach. So moisture is present but not an issue.
                      I have never had any foam collapse on me ever.
                      I mainly use SP-200-4 from SILPAK. It works great.
                      sigpic
                      PEACE, ADAM
                      www.poisonprops.com

                      Comment


                      • #12
                        Thanks Adam- I appreciate the info. I am still at a loss as to why I'm getting collapse on occasion. We just poured a few pieces in pretty high humidity with zero issues. Maddening.... Since we do so very little its really hard to get any practical experience.
                        How can a man die better than facing fearful odds, for the ashes of his fathers and the temple of his gods.

                        What you put into your mind- you put into your life.


                        www.zombietoxin.com

                        Comment

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