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Problems w/ body filler


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Need some advice on how to over come this snag. Essentailly I grafted one hood onto another and used filler strips of plastic to fill the gaps. Sanded it smooth then covered it in automotive polyester finishing putty. Sanded that down then added two coats of bondo glazing & spot putty. After sanding the bondo, I sprayed a few coats of primer hoping that i would have a smooth finish and no problems. As you can see, even after a couple coats of primer, you can see the lines through it. What do I need to do?

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I do a lot of heavy mods and bodywork, and I have a few ideas and suggestions you may want to consider.

1) The shrinking of the lines in your filler under the primer is a common problem. It occurs because of the difference in solvent absorbency and sensitivity between different materials. As Tom suggests immediately above, sanding the entire bad areas and re-priming, perhaps repeatedly, will most likely kill the ghosting eventually. It depends on what type of primer you use too, how wet you shoot it, how long you let it flash, and how long you give it to dry thoroughly.

2) To minimize this kind of problem in the future, try to fit your inset panels very well. Tight seams require less filler.

3) When you have your inset or spliced panels glued together and the glue is THOROUGHLY dry, sculpt the seam surface BELOW the level of the surrounding panels. This will allow you to fill the seam with your 2-part automotive putty, without the seams showing as they do on this work before it was primered. You'll then have a more even substrate that will tend to shrink at closer to the same rate.

4) Try to do your bodywork as perfectly as you can BEFORE you primer. Don't hesitate to fill and sand multiple times to get the surface as good as possible. 

5) You can do ALL your bodywork with the 2-part material. The single-part material is really pretty obsolete, is extremely sensitive to the solvents in primers and paints, and is well known to shrink and cause ghosting like you have here. Though some people still swear by it, to me, its ONLY use is for filling TINY pinholes and almost invisible flaws.

6) There's no easy guaranteed tricks to this stuff. Experiment to find techniques and materials that work for YOU every time. I've been doing custom bodywork on 1:1 vehicles and models for well over 40 years, and I could fill a book with tedious explanations of procedures most people aren't going to read and follow anyway. Practice and experiment, and DON'T TRY TO RUSH IT.

PS: I do know a little about this stuff. Here's one of mine...                 http://www.modelcarsmag.com/forums/topic/65965-mickey-thompsons-challenger-one-still-alive-feb-8/?page=1

Edited by Ace-Garageguy
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I do a lot of heavy mods and bodywork, and I have a few ideas and suggestions you may want to consider.

1) The shrinking of the lines in your filler under the primer is a common problem. It occurs because of the difference in solvent absorbency and sensitivity between different materials. As Tom suggests immediately above, sanding the entire bad areas and re-priming, perhaps repeatedly, will most likely kill the ghosting eventually. It depends on what type of primer you use too, how wet you shoot it, how long you let it flash, and how long you give it to dry thoroughly.

2) To minimize this kind of problem in the future, try to fit your inset panels very well. Tight seams require less filler.

3) When you have your inset or spliced panels glued together and the glue is THOROUGHLY dry, sculpt the seam surface BELOW the level of the surrounding panels. This will allow you to fill the seam with your 2-part automotive putty, without the seams showing as they do on this work before it was primered. You'll then have a more even substrate that will tend to shrink at closer to the same rate.

4) Try to do your bodywork as perfectly as you can BEFORE you primer. Don't hesitate to fill and sand multiple times to get the surface as good as possible. 

5) You can do ALL your bodywork with the 2-part material. The single-part material is really pretty obsolete, is extremely sensitive to the solvents in primers and paints, and is well known to shrink and cause ghosting like you have here. Though some people still swear by it, to me, its ONLY use is for filling TINY pinholes and almost invisible flaws.

6) There's no easy guaranteed tricks to this stuff. Experiment to find techniques and materials that work for YOU every time. I've been doing custom bodywork on 1:1 vehicles and models for well over 40 years, and I could fill a book with tedious explanations of procedures most people aren't going to read and follow anyway. Practice and experiment, and DON'T TRY TO RUSH IT.

PS: I do know a little about this stuff. Here's one of mine...                 http://www.modelcarsmag.com/forums/topic/65965-mickey-thompsons-challenger-one-still-alive-feb-8/?page=1

Ace, can you post up a picture of the two part putty you use? Or post Manufacturer and product numbers of the stuff you use?

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Ace, can you post up a picture of the two part putty you use? Or post Manufacturer and product numbers of the stuff you use?

Yes sir. The 2-part Bondo "Professional Glazing and Spot Putty" is my primary go-to product now. It's the most fine-grained of all of the similar products I've ever used, which makes it ideal for model work. It's also rather thinner (lass viscous) and spreads easily, and tends to self-level. The thinness of the product makes it a little tricky to do heavy vertical fills, but if you use your brain and let gravity help, you're golden. It also adheres VERY well to styrene that's been sanded with 180 grit paper. The last, and possibly best, feature of the stuff is that besides coming in 1:1 shop-size containers, it also comes in modeler-friendly tubes (with the catalyst in a separate tube, included, as always with 2-part fillers). Available in most real-car-parts chain stores.

bondo-professional-glazing-spot-putty-80

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Everything Bill said plus;

Use the tiniest bit of hardener in your mix. You just want it to turn very slightly pink - or you will have no working time. It will kick too fast. If it does, mix another batch; don't try to use it.

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So "ghosting" is my problem. I will try to fill with superglue then sand and see what happens. Bill, The bondo putty you pictured is the same that I used on this hood. Normally I use Dupli-color high build gray primer following body mods like this and its usually successful. This time I used a normal duplicolor gray which the results you see....  For future reference If I use a "primer sealer" would it prevent ghosting?

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Quick & easy solution to your problem at this point: Fill your lines with superglue.

Do it right over the primer. Sand down into the primer, reprime, repeat as necessary.

I use super glue, ZAP, to be exact and this suggestion is solid.  I have great results, and it is much faster than using putty and easy to sand.

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 Bill, The bondo putty you pictured is the same that I used on this hood.

It's not the same as what you said in your ORIGINAL post, which is what I went by. 

Precision in communication is important, especially when you're trying to get technical advice and information.

 

In your ORIGINAL post, you say you used "bondo glazing & spot putty", which is this SINGLE-part product, #907. It's RED.    attachment.php?attachmentid=116620&d=135

Looks kinda like the same package, NOT AT ALL THE SAME. The product I recommended is Bondo Professional Glazing and Spot Putty #801, which is buff when mixed properly.

Good luck.B)

 

Edited by Ace-Garageguy
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Well, it's not the same as what you said in your ORIGINAL post, which is what I went by. Precision in communication matters.

 

In your ORIGINAL post, you say you used "bondo glazing & spot putty", which is this SINGLE-part product, #907. It's RED.    attachment.php?attachmentid=116620&d=135

Looks kinda like the same package, NOT AT ALL THE SAME. The product I recommended is Bondo Professional Glazing and Spot Putty #801, which is buff when mixed properly.

Good luck.B)

 

Yep, notice Bills fromage says "Proffesional Glazing and Spot Putty" plus its in 3oz.  Were as the stuff you have (as do I) simply says "Glazing and Spot Putty" and is in 4.5oz.  I've had shrinkage with it as well but I do like the stuff.  Here it is what I have and what you probably do to for ref;

http://bondo.com/bondo-glazing-spot-putty-907.html

 

 

Edited by aurfalien
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The issue I find with using super glues as filler is that it sands at a different rate than the primer around it, sometimes leaving it's own edge to repair. One of the things I do with very small imperfections is fill them with the same primer that you have used.  Sometimes a dab of it into a small imperfection,  like a rain drop placed from a toothpick, will dry down a bit and the remainder will be easy to sand blending right into the surface around it. I've also taken same primer, sprayed into a small cup and left to thicken up a bit as it dries out. This works well too.

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