1. pishta

    pishta I know I'm right....

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    WTH? I mixed up a small 3" round x 1/2" pad of 3M Bondo and mixed it up with a 3" stripe of hardner as described in instructions. Mixed it for about 2 minutes and by the time I was slapping it onto the dent it was not even spreading anymore, just clumping and way harder than I remember it. Whats the official ratio of hardner to filler? I got a scale and will use about 3/4 the hardner called for next time for some longer set up if that works. Im putting it on a horizontal surface so I can have it a little runny as long as it gets into the screen. Im patching a 3" rust hole (double wall, top is rusted through) in my little beater truck.
     
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    • Kern Dog

      Kern Dog FABO Gold Member FABO Gold Member

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      It varies with temperature and humidity. I find that it is a pretty wide ratio with a LOT more filler than catalyst. Colder weather means a LOT slower setup, just like concrete.
      Next time, consider a better body filler like Rage Gold. Most fillers will shrink a bit over time but Rage seems better. It spreads and sands better too.
      Funny aside.....
      Years back I was doing bodywork and popped the cap off of a BONDO can. Inside was the catalyst and an offer to get a FREE red BONDO jacket with proof of purchase of 10 of their 1 gallon cans. I laughed at the thought of the guy at the car show bragging about his car while wearing a jacket that shouts just how much body filler is in his car! You might as well wear a Preparation H jacket or something equally humiliating!
       
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      • pishta

        pishta I know I'm right....

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        80F here, $12 to fill a few holes and VatoZone was skateboard distance so.......I remember paying 2 guys $100 in 1991 to fill all the dents on my 57 Ford Jalopy. I dont think they use any hardener as the gray filler was still fingernail soft after a week! :BangHead:
         
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        • 70 Buster 340

          70 Buster 340 Carbon Footprint FABO Gold Member

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          Was the can opened before ?
           
        • pishta

          pishta I know I'm right....

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          new can
           
        • ChrisRomello

          ChrisRomello Well-Known Member

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          You only need a little bit of hardener. Plop a round blob on a mixing board and then the hardener you mix in should be a line about 1/4 the diameter of the blob of filler.
           
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          • Tooljunkie

            Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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            Some fillers harden pretty quick now. At least the stuff i got from the body shop. When it starts to tighten up, its done. Golf ball size glob, 3/4” strip of hardener.
             
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            • CFD244

              CFD244 These pretzels are making me thirsty. FABO Gold Member

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              2 minutes of mixing sounds long to me?
               
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              • pishta

                pishta I know I'm right....

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                says 3-4 minutes mix/set up time, man I though it was like 10? not a deal killer, I just ended up putting 3 coats on it. Shit is hard as cement to sand manually. Well see tomorrow.
                 
              • Tooljunkie

                Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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                No, not 10. Maybe white lightning from 30 years ago.
                Not much working time, so mix smaller amounts or move faster.
                 
              • Ottmundr

                Ottmundr 68 Fastback

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                Just mix the bondo with the hardener until the colors are all mixed together. You have about a minute from that point until you can't work it.

                A squeegie for mixing, cardboard for the mixing board. Why spend the money on the mixing paper board if you aren't doing repairs constantly? I just used cardboard scraps when doing repairs on drones.
                 
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                • pishta

                  pishta I know I'm right....

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                  last bondo job I did was in high school auto shop...1985! All my cars have been straight, that's been a prerequisite as I'm no body man!
                   
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                  • RustyRatRod

                    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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                    I always go with "around" a 3 to 1 ratio and it works fine.
                     
                  • pishta

                    pishta I know I'm right....

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                    hold up, 3:1 as in 3 inch filler puddle to 1" hardner squirt?
                     
                  • MOPAROFFICIAL

                    MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                    Hey now.. I wear my Prep H jacket everywhere I go and the people say I look "slick" and "bad ass" in it... I just wish I could get the chilli stains off it..

                    Lmao
                     
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                    • RustyRatRod

                      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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                      yeah
                       
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                      • Kern Dog

                        Kern Dog FABO Gold Member FABO Gold Member

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                        More like 10 to 1.

                        painting-101-understanding-plastic-fillers-2019-02-19_02-36-45_956999-960x768.jpg
                         
                      • Treblig

                        Treblig Well-Known Member

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                        The reason it got hard so fast is that you probably used this hardener:

                        upload_2021-11-21_20-4-46.jpeg
                         
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                        • pishta

                          pishta I know I'm right....

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                          No, I need it to last longer than 10 minutes! :rofl:
                           
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                          • Treblig

                            Treblig Well-Known Member

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                            Just use more hardener!!!!!!!!!:poke::rofl::rofl::rofl:
                             
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                            • Dana67Dart

                              Dana67Dart The parts you don't add don't cause you no trouble FABO Gold Member

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                              This post has gone into a hole
                               
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                              • DFX 340 Duster

                                DFX 340 Duster FABO Gold Member FABO Gold Member

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                                Well, pishta was trying to get it into a hole anyways.
                                 
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                                • Joey4speed

                                  Joey4speed FABO Gold Member FABO Gold Member

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                                  I bet that's a "members only" style jacket too.
                                  Very cool.
                                  Lol
                                   
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                                  • George Jets

                                    George Jets 1967 Dart 2 Door FABO Gold Member

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                                    Too much hardener on a hot day.

                                    So you had 3 times the amount of recommended hardener.

                                    The hardener (like peroxide) is the catalyst that makes it dry.

                                    At 80° the catalyst Works 4 times faster than it does at 65°.

                                    If your mixing Board is hot from sitting out in the sun, that speeds up the reaction time by 10 fold too.

                                    Good luck. When you can scratch the bondo with a finger nai and it leaves a white scratch. That is the time to start working it before it gets super hard. Like hitting it with 36 grit on a sanding Block to bring it to shape.

                                    Then when to shape let it fully harden, and final sand with 80, and 180, feather edge the area and it's ready for primer. Then block sand that.
                                     
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                                    • pishta

                                      pishta I know I'm right....

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                                      @George Jets That's the thing, I used the hardener exactly as stated on can. I just remember it setting up much slower. Maybe it was the heat as I had Autoshop 2nd period and it was still pretty chilly in that massive garage. Still got over half a can and 2 more holes to fill so Ill get it 'right' one of these times.
                                       
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