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  1. Member Since
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    Sep 19, 2007, 9:19 PM - BODY FILLER / BONDO (Drying time...)??? #1

    If not enough hardner is added, I assume this will eventually dry by itself/???

    Does heat help, if that seems to be the case?

    (And what's the right ratio to add of the hardner? - The tube seems small for the contents of the can)

    It's also a little old - Does that play a factor?

    THANKS!
  2. clonesix's Avatar
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    Sep 19, 2007, 11:41 PM - Re: BODY FILLER / BONDO (Drying time...)??? #2

    Yes, it will harden eventually, but if you get tired of witing, just scape it off and put better catalyzed bondo on it.

    Better to go by color than amout or %. You should have a nice pink color, roughly the color of the plastic spreader.

    You should lessen the hardner for large batched, or warm temperatures.
  3. Member Since
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    Sep 20, 2007, 7:59 AM - Re: BODY FILLER / BONDO (Drying time...)??? #3

    My mix is gray from the can - With a blue tube of hardening liquid...
  4. propcicle's Avatar
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    Sep 20, 2007, 8:26 AM - Re: BODY FILLER / BONDO (Drying time...)??? #4

    You generally mix it until it has a consistent color - normally kind of a salmon colored pink. I haven't seen the blue. It will start to "rubberize" pretty quick and it does get warm. Normally it's pretty hard and good for sanding within 15-20 minutes.

    As for it being old - does it still smell really bad, kind of a petroleum smell? If so, it's probably ok. That stuff reeks!
  5. TK1536's Avatar
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    Sep 20, 2007, 8:49 AM - Re: BODY FILLER / BONDO (Drying time...)??? #5

    I've got a can that I've been using for over a year and a half and it's still good. I had to mix it up a few times because it separated, but it still does the job. I'm surprised the dead don't rise when I open the can.
  6. ArtisanProps's Avatar
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    Sep 20, 2007, 9:55 AM - Re: BODY FILLER / BONDO (Drying time...)??? #6

    Bondo should start to harden Pretty fast, usually within 5 minutes. Of course the cure time depends on the amount of hardener. If your having Problems either it wasn't mixed good enough or the can you have is no good (old)
  7. Member Since
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    Sep 20, 2007, 11:36 AM - Re: BODY FILLER / BONDO (Drying time...)??? #7

    Been a few days - And still a little bit pliable...

    I had not used it or mixed it in a while, so was a bit conservative with the hardener...

    Will heat assist this at all (i.e a few passes with a heat gun), or will that not do anything?
  8. TheGreenMachine's Avatar
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    Sep 20, 2007, 12:01 PM - Re: BODY FILLER / BONDO (Drying time...)??? #8

    Heat generally will help, but in your specific case not in the sense of giving it a few passes with the old heat gun. Think a more stable application of heat over a longer period of time.

    Generally if you could place it somewhere warmer it will help catalyze and spead up the cure. Or in your case any potential cure it might have left. For example if you had a deck or someplace where you could let it set out in the sun for a period of time that could help.

    Or in my brothers case he has a utility closet that contains his hot water heater, washer, and dryer. That room is always a good 10 degrees warmer that the rest of the house. We had some old resin we used as structural filler inside some stuff and we just sat the items in that room for a few days and they cured. This was resin that originally had about a 30 min set 2 hr cure.

    - TGM
  9. CustomCreations's Avatar
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    Sep 20, 2007, 12:03 PM - Re: BODY FILLER / BONDO (Drying time...)??? #9

    General guide-
    Pea size ball of hardener to golf ball of filler.

    If you are using old filler, which is a little dry, you can mix a bit of fibreglass resin into the mix to thin it up a bit too.
  10. JBReplicas's Avatar
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    Sep 20, 2007, 1:56 PM - Re: BODY FILLER / BONDO (Drying time...)??? #10

    TK1536 said: View Post
    I've got a can that I've been using for over a year and a half and it's still good. I had to mix it up a few times because it separated, but it still does the job. I'm surprised the dead don't rise when I open the can.
    LMAO Thats funny cos I was thinking the same thing when I ripped open my 2 year old can this afternoon, honest if I hadn't have gotten it open by hand dynamite was next on my list
  11. ArtisanProps's Avatar
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    Sep 20, 2007, 3:28 PM - Re: BODY FILLER / BONDO (Drying time...)??? #11

    Now I'm not an expert on Bondo but if it's anything like Resins, then here's what usually happens when you add the hardener..

    The resin contains a chemical that keeps it in a liquid or Pliable state. the catylist or hardener once mixed with the Resin starts a reaction that burns or evaporates the Chemical in the resin (keeping it Liquid) away making it turn to a solid..

    So that being said if your Bondo is still Pliable, I think your hardener might be bad, or else it should have turned hard by now. Even a little bit of hardener mixed with the bondo should still make it hard. It would just take a little longer for the hardener to evaporate the chemical away...
  12. pennausamike's Avatar
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    Sep 20, 2007, 4:37 PM - Re: BODY FILLER / BONDO (Drying time...)??? #12

    In my experience with both cars and props, setting a bondo'd piece out in the sun will aid in curing.

    I don't know if the UV in addition to the heat makes a difference, but sun seems to work better than just heat.

    Also, I always try to give my bondo'd stuff 24 hours to dry before sanding.
    Maybe not necessary, but I think it makes a difference.

    Mike
  13. Treadwell's Avatar
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    Sep 20, 2007, 4:53 PM - Re: BODY FILLER / BONDO (Drying time...)??? #13

    Aren't we talking about a chemical process rather than "drying"? In that case, setting it in the sun or a warm place works not because it's "drying" (evaporating water) but rather the heat is helping the chemical reaction. I doubt UV has anything to do with it.

    I guess the difference is academic, though.
  14. ArtisanProps's Avatar
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    Sep 20, 2007, 7:09 PM - Re: BODY FILLER / BONDO (Drying time...)??? #14

    Yes Heat does have some effect on resins..
    for instance if you try and cast something in a cold silicone mould without warming the mould first. The silicone will actually absorb the heat, and usually leaves the surface of the part being cast sticky and uncured and to say UV has anything to do with a faster curing Process I'm not sure because some glues actually harden instantly with UV Light, so it's possible

    It is a chemical reaction but at the same time the chemical that keeps the resin liquid is being evorporated by the catylist making it hard and that's why if your hardener goes bad your part stays sticky or doesn't cure Properly
  15. Ghost of Christmas Dinner RPF Premium Member dbuck's Avatar
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    Sep 20, 2007, 9:10 PM - Re: BODY FILLER / BONDO (Drying time...)??? #15

    If your bondo hasn't hardened after a few days, nothing will help it now. Start over. Actually, bondo should be pretty darn hard and sandable after 15 minutes and well cured in a day.
    Before using bondo check and see if it has separated at all, and if so, stir it up. The stuff lasts forever if the can gets sealed back up properly. I've got a couple different types of bondos that are well over 8 years old and I still use them occasionally with no issues.


    David
  16. Darth Stone is offline Darth Stone
    Sep 20, 2007, 11:12 PM - Re: BODY FILLER / BONDO (Drying time...)??? #16

    A lot of good advice here folks. I have been in the auto body repair field now for over 25 years and have never used bondo that was more than a year old. The stuff is just way to cheep to keep it around that long. And it always is more of a pain in the rump to revive it with fiberglass resin because you end up with a material that will cure harder than it would have before. So be prepared to sand a bit longer if you go this route.

    My thoughts are if your bondo hasn't hardened in an hour or so that you should just scrape it off and try again. As said before in other post's, it could be just to old. Either the hardener or the bondo itself, or both.

    My rule of thumb for adding the hardener is if you have a round pile say the size of a drinking glass coaster. Just run a bead across the center about the width of the shaft of a Q-tip. Mixing is also important. You need to end up with a uniform even color throughout the mixture.

    And if I may add just one last thing. If when you are spreading the stuff and it starts to kick on you, just bite the bullet and quit. Toss it out and make another batch and you will be glad you did.

    DS
  17. Member Since
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    Sep 21, 2007, 6:13 PM - Re: BODY FILLER / BONDO (Drying time...)??? #17

    I did see UV hardening Bondo in the store. Won't harden unless it's in the sun. Good for the handyman who works slow.

    I believe it is 'catalyzing'. So it would harden very slowly. It hardens in the can without hardener.
    On some fiberglass that wouldn't dry I smeared hardener over the surface and it soaked in or something and kicked off.
    You can add enough fiberglass resin to make a pourable mix for molds. Helps with fine detail.
  18. Member Since
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    Sep 21, 2007, 11:44 PM - Re: BODY FILLER / BONDO (Drying time...)??? #18

    So is the bottom line that if left alone without any hardening agent (or not enough) the base will not set - ever??????
  19. Darth Stone is offline Darth Stone
    Sep 22, 2007, 12:00 AM - Re: BODY FILLER / BONDO (Drying time...)??? #19

    I'm sorry Terryr, I don't want or need to pick on you or others who are just messing around with, "bondo". But the methods that you have just described are only a band aid kind of approach to the material. And should in my opinion never be taken as a workable method of working with automotive type fillers or fiberglass, again IMO. I don't want to upset you or anyone, but you must consider what you want a material to do before you use it. And then be prepared to waist some practicing how to use it before you commit it to a project.

    My Father always said to his two sons, "If you don't build it with your best effort, don't build anything larger than a garbage can."

    RIP Dad
    Dan Stone
    1936-2006
  20. Member Since
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    Sep 22, 2007, 12:23 AM - Re: BODY FILLER / BONDO (Drying time...)??? #20

    Not a bother to me... And I am not experimenting with adding any fiberglass or anything...(Perhaps other conversations went there)

    I simply want to know - If bondo is set to cure, without enough hardening agent...

    i.e. will it harden by itself? (regardless if enough hardening agent was placed)
  21. Darth Stone is offline Darth Stone
    Sep 22, 2007, 12:25 AM - Re: BODY FILLER / BONDO (Drying time...)??? #21

    In a simple word,..No.
  22. Member Since
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    Sep 22, 2007, 11:52 PM - Re: BODY FILLER / BONDO (Drying time...)??? #22

    Roger that...

    Just didn't know if hardener was just a catalyst to speed up the drying process, or a necessary element in accomplishing such.
  23. Darth Stone is offline Darth Stone
    Sep 23, 2007, 12:30 AM - Re: BODY FILLER / BONDO (Drying time...)??? #23

    Hardener is just a catalyst, is causes a chemical reaction within the material that makes it harden.
    Another old trick that I will pass onto all of you. If you are doing a large area and you a heavy buildup. If you knock it down with lets say 40 grit just as it starts to get hot but not 3/4 hard yet, you will save some sanding time.
    And adding polyester resin to bondo changes the chemical make up and can cause problems in adhesion and even to the paint. It can even cause the filler to shrink or become brittle. I have seen problems with cars that come back weeks, or even years later that the paint has changed color over the area that had been repaired using body filler. Thankfully no one that I have seen still does this
    Sorry, not trying to sound like a know it all. But in this case I allmost do2 cents

    DS
  24. Member Since
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    Sep 26, 2007, 1:40 AM - Re: BODY FILLER / BONDO (Drying time...)??? #24

    Darth Stone said: View Post
    I'm sorry Terryr, I don't want or need to pick on you or others who are just messing around with, "bondo". But the methods that you have just described are only a band aid kind of approach to the material.
    I know it's a bandaid Darthstone. That's what this thread is about.
    And Body filler is made with polyester resin, so mixing it with polyester resin shouldn't hurt anything.
    [And the bodyman I grew up beside won many awards at car shows. But what does that have to do with anything?]
  25. Member Since
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    Sep 26, 2007, 2:12 AM - Re: BODY FILLER / BONDO (Drying time...)??? #25

    For future reference, I looked up a few MSDS on body filler.

    Unsaturated polyesters resins, modified resin, color pigment, stuffing, anti sediment materials, auxiliary agent and firming agent. mixing ratio 100: 2.

    Styrene 15-20% Non Fibrous Talc 32 -42%, Calcium Carbonate 1-10%, Glass beads 1-10%, Amorphous Silica 1-3%.


    "In the mid 1950s the first polyester based car body fillers were developed. They were made from the same fiberglass resins used to make boats. The first successful filler was called 'bondo' and was 40% polyester resin and 60% talc."

    Polyester and Talcum powder. Not very fancy.

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