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Technical Bondo woes

Discussion in 'The Hokey Ass Message Board' started by 36roadster, Feb 5, 2015.

  1. I was patching up some holes/ scratches on a fiberglass panel and layed some bondo on it (not overly thick). I let it go overnight, but when I had a poke at it the next day, it was still sticky, you could scrape your fingernail across it and end up with some under there. I realised then that the stuff I used was probably "off" (or maybe the hardener was). Will the stuff eventually harden up? If it is to stay sticky, whats the best solvent I can hit it with to remove this mess?
    The weather forecast for here is about a week of over 100 degrees, maybe that will help?
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 44,023

    squirrel
    Member

    Acetone usually works, but it might affect what's under the filler. If the hardener is old, it doesn't work very well. "Old" means older than about 6 months.
     
  3. alchemy
    Joined: Sep 27, 2002
    Posts: 14,580

    alchemy
    ALLIANCE MEMBER

    You've used bondo before, right? You aren't just talking about the tacky surface are you?

    If it's soft all the way through, I'd scrape most off with a chisel. Grind the rest with an old disk. Then throw the disk away.
     
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 44,023

    squirrel
    Member

    Some brands have a slightly tacky surface when they harden, others don't.
     
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  5. john worden
    Joined: Nov 14, 2007
    Posts: 1,491

    john worden
    Member
    from iowa

    In this situation I've applied a thin layer of filler mixed with extra hardener over the soft filler. It'll harden up.
     
  6. porknbeaner
    Joined: Sep 12, 2003
    Posts: 41,341

    porknbeaner
    Member

    Remove it with a putty knife and get some new hardener and do it again. it is usually the hardener that goes bad as it is the catalyst.

    SA trick that a body and fender man/fiber glass body builder told me about bondo on glass is to mix it with fiber glass resin and hardener. 3:1 bondo to glass. It is just the way that he does it, it may not produce the results that you require.
     
  7. Two more trains of thoughts,If you are familiar with Bondo and have used it in the past,did you use enough hardener and how cold was your shop,cold weather will greatly reduce drying time. HRP
     
  8. I am guessing that it was not cold enough in his shop in Australia during the summer to slow the cure down to a days time.:D
    It could just be the skim on the top that stays sticky. Some lower quality fillers don't have the additives required to stop that from happening. Try sanding it, if it remains soft and clogs your paper after that first top coat has been removed then you need to take all off. If it is fine after that initial sanding it will be fine but you might want to buy better filler in the future as sand paper ends up costing much more than filler when you have to throw it away all the time because your filler clogs it up. If it is still soft, as mentioned, it is probably bad hardener. Scrape or sand it off and start again. Make sure you use enough hardener 2% by weight and never store your hardener where it is exposed to UV as that increases the deterioration of MEKP substantially.
     
    Last edited: Feb 5, 2015
    waynos likes this.
  9. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 23,761

    Jalopy Joker
    Member

    post a pic of what you are working on, and "bondo" used
     
  10. No filler that is properly catalyzed is taking overnight to cure at 50 degrees.
     
  11. My daughter let some of those "traveling" body men do a fix on her pickup. They bondoed it up, primered it and sprayed on a guide coat. She never got it repainted. When we junked the truck 10 years later, you could still dig the bondo out with your fingernail.
     
  12. Body filler is talc, like baby powder, if it isn't covered with real paint (not primer) it will absorb water like a sponge. I am not surprised it was soft after 10 years of exposure.:rolleyes:
     
  13. oldcarguygazok
    Joined: Jun 20, 2012
    Posts: 401

    oldcarguygazok
    Member
    from AUSTRALIA.

    When I do scratches or pinholes,i use an ultra fine glaxing putty or a stop putty,only those with hardeners,with body fillers[bondo]they are cheap,so get quality stuff,if it's tacky after 10-15mns =not enough hardener or it's too cold,should be min 24d cel,make sure from the start you press the filler firmly into those small areas so it gets right in,good luck,Gaz!
     
  14. DOH!...Just because it's the dead of winter in my neck of the woods don't mean everybody lives where it's cold where they are...o_O HRP
     
    pitman and oldcarguygazok like this.
  15. rdemilt
    Joined: Jan 12, 2009
    Posts: 132

    rdemilt
    Member
    from so florida

    If the fiberglass panel is made with Epoxy resin not polyester resin the bondo will never harden. Plastic Filler is polyester base and the two don't work together. One way to get thru your problem is to lay a good coat of epoxy primer on the fiberglass panel and bondo on top of it. you will need to Scrape it off clean wash it with acetone and start fresh.

    You can put epoxy resin over polyester resin but not polyester resin over epoxy.
     
  16. blowby
    Joined: Dec 27, 2012
    Posts: 6,116

    blowby
    Member
    from Nicasio Ca

    Interesting, I would have thought you could drop a blob of catalyzed bondo in oil and it would still cure. Cures in my hair overnight.

    BTW have you tried urinating on it? I see guys doing bodywork and they often say "Piss on it" right after applying bondo.
     
  17. This is not true if the epoxy is already cured. You cannot mix the two resins but they will not affect one another once cured.
     
  18. 4ever18
    Joined: Nov 1, 2007
    Posts: 466

    4ever18
    Member


    LOL!!!
     
  19. mike bowling
    Joined: Jan 1, 2013
    Posts: 3,440

    mike bowling
    ALLIANCE MEMBER

    Moisture and humidity can affect drying time for filler too.Interesting post about pissing on it; that must be why body shop guys usually drink lots of beer- then they'll never run out of "curing fluid" !! DSCN2087.JPG
     
  20. ol'stinky
    Joined: Oct 3, 2010
    Posts: 258

    ol'stinky
    Member
    from New Jersey

    Just scrape it off and clean the rest off with some lacquer thinner and a scotch rite pad. Please don't piss on it. Don't listened to anyone telling you to put more on top, that will not work and will just create an unstable surface and WILL fail sooner rather than later.
     
  21. Slopok
    Joined: Jan 30, 2012
    Posts: 2,335

    Slopok
    Member

    Try some fresh Rage if available in your area. Best there is.
     
  22. It looks like I got me a bit of scraping to do. Iv'e used bog for years, but it has always behaved itself. It sounds like the hardener has crapped itself. The layer is only 1mm thick, and it is soft all the way through.
    It would have nothing to do with the temperature, it's a pleasant 97 degrees outside, but it will get hot next week.
     
  23. 48FordFanatic
    Joined: Feb 26, 2011
    Posts: 1,336

    48FordFanatic
    Member
    from Maine

    OMG .....it must be brutal down there is SC in the " dead of the winter". What ....40 degrees over night for a low....20 below here this morning.
     
  24. 48FordFanatic
    Joined: Feb 26, 2011
    Posts: 1,336

    48FordFanatic
    Member
    from Maine

  25. rdemilt
    Joined: Jan 12, 2009
    Posts: 132

    rdemilt
    Member
    from so florida

    Sir I am not trying to get off topic of start a dispute, but I disagree 100 % with your statement. Vinylester resin is the only other option when trying to cross both Epoxy or Polyester. Vinylester will coat over the top of either dried product and harden appropriately.

    I do agree with you that the products cannot be mixed in liquid form.
     
  26. alchemy
    Joined: Sep 27, 2002
    Posts: 14,580

    alchemy
    ALLIANCE MEMBER

    I usually say "piss on it", put down the hammer and dolly, and that's when I get the bondo out. Maybe the wizz is a good bonding agent?
     
  27. You may disagree but you are incorrect. I work for a filler company and I am pretty well versed in what our products can be used over and a fully cured epoxy will have zero affect on the hardening of a body filler Not to be a dick but to make sure I was not talking out of my ass and spreading false info I called our lab to confirm and they concurred with my statement. Now an Epoxy that is not fully cured will result in these types of situations.
     
  28. oldcarguygazok
    Joined: Jun 20, 2012
    Posts: 401

    oldcarguygazok
    Member
    from AUSTRALIA.

    Imo,filler will cure layed down on most surfaces but not necessarily bond to it,i've used it many a time to repair cracks and chips on my workshop floor[concrete]still good after 20plus yrs !
     
  29. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,423

    gimpyshotrods
    Member

    Please tell me you are using a professional-grade product and not a Bondo branded product, from the auto parts store.
     
    Last edited: Feb 6, 2015
  30. rdemilt
    Joined: Jan 12, 2009
    Posts: 132

    rdemilt
    Member
    from so florida

    OK
     

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