"Sweating" resin copy?

Discussion in 'General Modeling' started by trekkieb47, Aug 3, 2005.

  1. trekkieb47

    trekkieb47 Well-Known Member

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    I made my first "pull" (slang for copy from a mold) yesterday on my SPD Badge.

    Too bad it came out like @#$%.. It looked great at first, absolutely clean and an exact copy from the master. Only problem was that I noticed in a couple areas it looked "wet". Keep in mind this is well after the cure time, so I know it was fully cured. But was it? I rubbed a couple of these wet spots off... particularly one minute pin * spot on the "dog face" part of the badge. And oddly I could see the wetness come back, like the resin part was sweating.

    I soaked it in warm water... thinking the heat would activate the resin some more and finally make the sweating go away. It worked for awhile. I put it away in the garage and went to bed.

    Woke up this morning and it was really "sweating" bad.

    Yargh.... I'm going to start making multiple molds of the badge after I clean up a couple spots on the master... but what good will these molds be if the resin isn't right?

    Any suggestions?
     
  2. blufive

    blufive Sr Member

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    What kind of resin are you using?

    You *might* be able to clear coat the piece and stop the weeping but I'm not sure.

    Did you mix the chemicals as long as the directions say?
     
  3. captain america

    captain america New Member

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    The reason your resin is "sweating" is because the two catalytic components weren't mixed thoroughly. This happens frequently with Smooth On and Polytek resins.

    My suggestion: before doing another casting, shake both containers thoroughly(about 1 minute), prior to mixing, and then be sure to mix both parts (A & B) thoroughly as you're casting. This will eliminate your problem.

    Should the sweating reoccur even after you've followed the steps above, contact the vendor of the resin to get a replacement batch.

    FYI: there's no overcoat you can put over sweating resin to stop it; it will continue to leech chemicals until the part simply begins to break-down, so throwing it out was the best thing you could do.
     
  4. cobywan

    cobywan Sr Member

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    Sweating it the worst thing to try and deal with. In the end trying to cover the junk is a waste of time.
     
  5. Jestefarean

    Jestefarean Sr Member

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    Yep...been there on this one...and it will die a painful death. In my experience Captain's explanation is always correct..but it gets worse. It happens because the chemicals in the resin (Smooth on321 is real bad) seperate in their seperate parts...so you need to really thouroughly mix part A and Part B before mixing ) and if you shake give it some time to deair too)

    Now, heres the problem. Lets say you don't thouroughly mix Part A before casting and get the sweating problem. This means you got to much of lets say component 1 for part A and not enough of component 2. As a result, you don't have enough component 1 any more in your part A jug and the rest of your casts can end up being sweaty as well.

    I'd recommened giveing the parts a good mix, and pour a batch into a cup or somethign you dont care about (no need to risk a mold) make sure it will setup for a day. If it won't, you may need to scrap your resin and get fresh stuff.
     
  6. blufive

    blufive Sr Member

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    I have fixed sticky paint that way so I thought it might work on resin, too.

    Oh well. :p
     
  7. CaptCBoard

    CaptCBoard Well-Known Member

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    I'm guessing the resin you are using cures to 'white' as opposed to 'tan'. The problem you are having is common to all 'white' resins. In extremes of heat or cold, the resin will go through chemical changes. Sometimes, not always, shaking the jugs before pouring will work. But quite often the real problem is the actual ratio of the mix you are using. All urethanes should be mixed by volume, not weight. The two components do not have the same specific gravity, so 10 grams of A will not be the same volume as 10 grams of B. If you have been mixing by weight, that is your problem because 'white' resin chemistry is very finicky. The best and most reliable solution to your problem is to switch to a 'tan' resin. I've never had a weeping problem with a 'tan' resin, unless the mix was WAY off.

    If you are already using a 'tan' resin, your problem is different. Most of the companies that sell resin to hobbiests, Alumilite being the only exception that I can think of, are reselling stuff they buy in bulk from a cheap supplier. The problem is, most of these 'repackagers' don't pay attention to what's going on in their warehouse. They buy the materials in 55 gallon drums and pot it off into the size you buy. But if their chemistry has been effected by temperature in their warehouse, they don't have a way to shake the big drums, so they sell the stuff anyway. At that point, the consumer is screwed because the component missing from what they bought is actually missing-- there's nothing to shake back into solution. Or, once half the material has been potted out, the separated components will be present in an increasing concentration as the drums become more empty, so again-- the stuff is still bad. Depending on how extreme the problem is, the consumer may only notice a slight brittleness to the part, or wind up with the problem you have.

    Remember this-- if you are planning on making something for sale, nothing will kill your business quicker than using cheap materials. They will always fail at some point and you will have unhappy clients.

    Scott
    CaptCBoard@AOL.com
     
  8. cobywan

    cobywan Sr Member

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    Vagabond is a very nice "tan" resin. It's stinky though. It smells like kerosine to me. But it performs very well. It smells better than that green stuff floating out there.
     
  9. Proximo

    Proximo Well-Known Member

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    This happen for me once, I didnt mix the resin enough.. and one part "sweating"
    I rubbed it of so it got clean, then i just filled the hole whit 2 part epoxy putty, and sanded it, Worked whit no problem for me.
     
  10. Treadwell

    Treadwell Master Member RPF PREMIUM MEMBER

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    Sounds like only a small portion was unmixed properly, then. If the whole thing had been...
     
  11. p0sitr0nic

    p0sitr0nic Well-Known Member

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    Ive found mixing just a little more curative into the mix than the actual resin chemical works well...

    And Im using white resin.
     
  12. trekkieb47

    trekkieb47 Well-Known Member

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    Forgive my inexperience... but which one is the curative? Part "A" or Part "B"?
     
  13. Treadwell

    Treadwell Master Member RPF PREMIUM MEMBER

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    Usually B. But it'll say on the container. Other words for curative: catalyst, accelerator.
     
  14. gonk27

    gonk27 Sr Member

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    Your problem really 'resin-ates' with me :p

    I agree it's a mixing problem as has been mentioned. Your case sounds quite extreme so I'm afraid your best best is probably to start again and chalk it up to experience.

    There might be a way out if a cast is sweating from just one spot. Depending on the shape of your cast, you might be able to gouge out the affected area carefully with a sharp knife then fill the hole you've made with filler or putty. I've done this and it works but if the sweating is too widespread that's another matter.

    Good luck.

    Jeremy
     
  15. Chris Martin

    Chris Martin Well-Known Member

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    I've had the tan resin do this too sometimes. If the resin starts to crystalise around the top of the bottles, when you open it, fine crystals often find their way in. If they get mixed in with the resin, they can sometimes promote the pinholes that "weep".
     

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