Why is my resin sweating?

Discussion in 'Replica Props' started by blufive, Mar 12, 2006.

  1. blufive

    blufive Sr Member

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    I've had this problem a few times now. I'm using Smooth On 305.

    With the last batch, my first two pours were "sweaty". I threw one away but kept the other. After a few days, the piece seems all right.

    I initially thought I was messing something up by shaking the containers (as per the instructions) and using it too soon. There's a froth that tends to go away after a few minutes.

    Today, I shook the containers and waited 30 minutes before pouring. My first few pours were fine and then I got another sweaty piece.

    I would have thought it was an error in my mixing but I stir everything at least 30 seconds.

    Like I said, some pours are good and some aren't.

    Any ideas?

  2. LeMarchand

    LeMarchand Sr Member

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    how long did you leave the containers be after you shook them (so from shaking till the bad pour). My experience is that the slower the kick of the resin, the faster part 'B' seperates and needs to be shaken before mixing again.


    TOSPHASER Sr Member

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    I have the same problem.........I would really like to know as well.

  4. Wolvster1

    Wolvster1 Sr Member Gone but not forgotten.

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    MANY factors can contribute to a " sweaty " part
    after you take it out of the mold...

    One, the Release Agent you are using will tend to build up
    and create a barrier that " can " make a part sweaty after
    a few pulls.. { IF your using a release agent ? }

    Also, I have found that certain RTV's after a certain
    number of pulls will start to sweat THEMSELVES and create
    that sweaty effect your talking about... They get dry and
    tough and when the heat from the resin curing creates the
    moisture in the mold..

    Also, theres the whole humidity issue
    that can effect the resin.

    The age of the resin ? Has the
    pre-polymer been exposed to air for too long ?

    THAT one is more of a dead give-away as the resin
    get "chunky" and pretty nasty .
  5. Sidewinder

    Sidewinder Sr Member

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    Stir the two parts in their containers before you mix em. Shaking doesn't always do enough.

  6. Blad

    Blad Sr Member

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    How big a pour are you doing?

    If it's a big pour (1kg+) then it may be kicking as you mix and you may not be mixing it thoroughly.

    If it's a small pour 50g or so then you shouldn't have a problem.

    I feel embarrased asking but you are mixing 50/50 by weight? It took me 6 months before I realised 50/50 by volume was wrong.

    Also as Wolvester stated if the containers have been opened for even a couple of weeks they'll have absorbed moisture and one of the parts may even be going 'crusty'.
  7. blufive

    blufive Sr Member

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    I let the resin sit 30 minutes before I poured this time but I have poured immediately after shaking in the past.

    I use mold release in some of the molds but not all. Some of the molds are not condusive to being sprayed because of their design.

    I know some resins are to be mixed by weight and some by volume, or at least, they have different mixing directions depending on HOW you're mixing. I don't see anything on Smooth On's website regarding this.
  8. Blad

    Blad Sr Member

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    I've never seen any resin that was mixed by anything but weight (once I knew what I was looking for.) But looking on smooth-on's site http://www.smooth-on.com/liqplas.htm it uses both volume & weight - that's inconvenient.

    I think what's clear is that there are a lot of possibilities and advice for what works with one product may not work with yours.

    It's also possible that the problem isn't your resin, but the mould - there's this piece of advice in the smooth-on FAQ:

  9. Replicator1701

    Replicator1701 Well-Known Member

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    I've found that if the resin is old it sweats. I use Poly-tech easy flow 60.
    The trick is to use it all right away after opening. Also dust your molds with baby powder before you pour.
  10. blufive

    blufive Sr Member

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    Thanks for the info, guys.

  11. PHArchivist

    PHArchivist Master Member

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    Because its nervous...?
  12. Kerr Avon

    Kerr Avon Master Member

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    Sounds like a bad batch.
  13. Funky

    Funky Master Member RPF PREMIUM MEMBER

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    I've had pretty good luck with 'weeping' resin pieces. Normally, you just throw it away and usually not worth trying to fix it. But sometimes you don't have that option and you just have to live with what you've got. Set the oven on the lowest setting (usually "warm") and put the piece in there. Keep it in there for a while. Here's where it gets tricky. There is no perfect science as far as how long to leave it in. I just check it about every 45 minutes. When I pull it out sometimes it's tough to tell if it's still weeping. I just wipe it off and put a fresh coat of primer on. This usually forces the weeping if it's still happening. If so, throw it back in and repeat. I've found that by doing this it usually dries the piece and stops the problem.
    JMProps likes this.
  14. Jedirick

    Jedirick Sr Member RPF PREMIUM MEMBER

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    I suspect the length of time between container shake and last pours has to do with the sweating. I'd swirl container significantly between each pour. Keeps bubbling low and ingredients from easily seperating.
    I don't think it is bad resin.

    May be some mold sweating as mentioned by smooth-on which could be occuring as mopold warms a bit more each time resin kicks.

    Still put my money on ingredient seperation.
  15. blufive

    blufive Sr Member

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    I've been gently shaking part B just before pouring. Part A is already in the cup. So far, I haven't had any more issues.

    JMProps likes this.
  16. maniacman7

    maniacman7 Well-Known Member

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    as stated already but had t oadd anyway, It could also come fro mthe mold itself since I use a 700 series from smooth-on for my molds and they tend t osweat as oppsed to silicon molds especially if they are used alot or you've just had them for a while.

    either that or you just Excite them too much ;););) :lol :lol


    FISHZILLA New Member

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    I know what the problem is...........................I've called Smooth on about this several times and I've finally figured it out. They said it could be this or it could be that, but then my supplier told me, "ya know, we have alot of problems with 305 doing that". So, now I use 300 and have never had the problem since. My supplier always tells me that 305 is just a very unstable resin. I gotta be quick with my 300 cuz it's faster, but I never have problems now.
  18. BrundelFly

    BrundelFly Sr Member RPF PREMIUM MEMBER

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    I had the same problem recently with SMOOTH ON.
    I figured, it was OLD RESIN.

    You can shake the crap out of it, OLD resin is OLD resin and its gonna weep.

    I switched back to SILPAK SILKAST 2 and have had no problems.

  19. propsculptor

    propsculptor Sr Member RPF PREMIUM MEMBER

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    I don't know why so many use Smooth-on, they are very expensive
    and the materials are not reliable time after time.

    I've used most brands out there working at different Studio shops
    and each shop has their preference, the one I prefer is also a Silpak brand
    called Sil-White.

    It's great stuff, you can easily tint it whatever color you want, and it still
    has no problems :)

    Last edited by a moderator: Nov 8, 2018

    MR BARLOW Well-Known Member

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    I use Pro Cast or Poracast Mark 2 from www.monsterclub.com , Ive never had a problem with either resin . , The Procast is great for slushing and the Mark 2 for smaller pours, it has a faster demold time.

  21. blufive

    blufive Sr Member

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    It looks like Silpak's website has been suspended so I can't check them out at the moment.

    Does anyone have their phone number?
  22. Jack Knight1979

    Jack Knight1979 Well-Known Member

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    I use 305 and have this problem once and a while. I've never had it with 300, i guess I'll have to switch back myself.
  23. thedap

    thedap New Member

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    the resin kicking will heat up the mold too, so after a few pulls the mold will be warmer if you aren't waiting very long.

    that makes a fast resin kick even faster, which can make a mold that has to be poured slow and manhandled a REAL pain to keep up with.

    my smooth-on resin was so old I had to STRAIN it while pouring it into the cups.

    still worked like it was supposed to....unfortunately, it was the fast stuff. :lol

    I have had problems before with the slow stuff getting alot more pinholes from "foaming" when it starts to kick and heat up. even in pressure casts.
    but that was with very high humidity days.

    and I've had weeping problems with the 305 too, and it was brand new (but who knows how long it sat at the distributor) but it was fine with tiny parts and open mold casts.
  24. propsculptor

    propsculptor Sr Member RPF PREMIUM MEMBER

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    These are the numbers I have: Silpak (818)985-8850 & (909)625-0056

  25. blufive

    blufive Sr Member

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