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  #76 (permalink)  
Old 11-19-2012, 06:04 PM
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Yes if it's a 2 part putty, If it's use straight out of the container that means it's a lacquer putty, very prone to shrinking after solvents hit it. If the cracks are extremely fine you could get away with the lacquer putty but again that technology dates back to Henry Ford. I would, sand the area with 180, squeeze the 2 part glaze into the cracks, and block them out, re prime, block and paint. Those cracks are usually in the paint, if the bumper was deteriorating it would look like a web, not straight lines. Make sure you get the glaze right into the cracks.

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  #77 (permalink)  
Old 11-19-2012, 06:51 PM
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I wondered, should I open the cracks up a little bigger with like a sharp knife or something? To give the the putty more to grab on to? Or should I skim over the whole affected area? And If I went the skim route, should I use something like >>>



??

The putty I have on hand is Evercoat metal glaze polyester finishing putty, Im assuming that might be ok for filling the cracks, but maybe not to skim with?? Trying to figure this all out and I do appreciate the help!!
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  #78 (permalink)  
Old 11-19-2012, 07:32 PM
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This is one of the reasons why I don't like leaving old paint on a vehicle that has a paint issue. I know it's a cover and they are a PITA to strip, but if they where stripped this would be a mute point. Without seeing how deep or wide the cracks are and the fact that it's got 1 coat of epoxy on it already and epoxy is basically a primer that is glue with rust protection in it, I would say that if you open up the cracks your asking for more trouble, the paint underneath cracked for a reason, it got hit, clear got brittle and no flex agent in it, (you mentioned that the bumpers had been repainted at one time and often shops don't add flex agent into the clear for bumpers and when they get tapped, the paint cracks). After you've roughed up your bumper with 180, take your catalyzed putty and your spreader and apply the putty length wise over the crack. It will in all probability make a raised line where the crack was. Then I would move the spreader and with putting pressure on the spreader go side to side until the line seems to disappear...let it set up and sand it down flush to the epoxy primer. You may have to repeat this on a few of the cracks, but when you have them filled, apply more epoxy primer, block and paint. This should get rid of your cracked cover...is it the right way, well it's a fix for what you have, the right way is to remove the damaged paint.

Let me know how it works.

Ray
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  #79 (permalink)  
Old 11-19-2012, 09:22 PM
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Gotcha, and Thanks. I should have sanded the bumper down further...but I was a little scared of it to tell you the truth. First time fooling with this Urethane stuff... I'm into "old" cars...lol
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Old 11-20-2012, 07:47 AM
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Quote:
Originally Posted by 69 widetrack View Post
Yes if it's a 2 part putty, If it's use straight out of the container that means it's a lacquer putty, very prone to shrinking after solvents hit it. If the cracks are extremely fine you could get away with the lacquer putty but again that technology dates back to Henry Ford. I would, sand the area with 180, squeeze the 2 part glaze into the cracks, and block them out, re prime, block and paint. Those cracks are usually in the paint, if the bumper was deteriorating it would look like a web, not straight lines. Make sure you get the glaze right into the cracks.
When fixing cracks in bumper covers be absolutly sure to use a wax & grease remover a few times and blow the excess out of the cracks with an air bolwer before doing anything,wax gets caught in those cracks and they will reapear later on as the filler looses adheasion maybe a couple weeks...two part putty like ez sand will work well but break if the bumper hits something ,theres another one called flexible putty made for bumpers ...What I would do is prep the bumper for epoxy and really lay it down on the cracks so it'll flow down into them and fill them, then do my filler work with the flexible puttyand prime again...Putty seems to just sit on top and not really fill the cracks...epoxy primer is the most flexible primer out there....
Unfortunately your using Sumit materials which I know nothing about with the exception of they target DIY's just like duplicolor and Eastwood does so I have little faith in it ,even though summit may or may not be good stuff I dont know what it can do BUT normaly with Spi I'll start blocking (after priming the metal) with dry block with180 finding all dings and imperfections then doing the filler work and using a few more coats of epoxy I'll then wet block with 400theres really no need for any build prime rspi sands easy and builds...2k or build primer tends to chip easilybut after making the (epoxy sandwitch) Thats when you would want to use the build primer if thats what you want to use
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  #81 (permalink)  
Old 11-20-2012, 10:17 AM
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I agree with much of what your saying, especially the wax and grease remover to be blown out of the cracks. Depending on the crack, I don't know if I would use it at all for exactly the reason you stated. Wipe and the bumper down with a dry rag, and then do your repair, eliminate the E&GR completely and you don't have the problem leaving it in the cracks by accident and having a future adhesion issue, that's why I never suggested it.

Bridging epoxy or any over cracks is an option, however, the hair line cracks reappeared where excencuated after the first coat of epoxy and didn't fill them, and without seeing the bumper, would tell me that they are a hairline crack as the epoxy he's using is thick and in most cases should bridge a crack line. I don't like bridging at any time but, the bumper wasn't stripped and here we are.

Your right, putty will has a tendency to sit on top and break if it gets hit and that's the scary part of not stripping a bumper with original paint issues. You or I don't know how thick the hair line cracks are, if they are really tight, and he is using a an epoxy primer that has a fair amount of build, chances are it's not going to flow inside the cracks leaving air trapped in the crack and when warmer weather hits the air trapped in the crack will expand and may become visible, or over time could cause a lack of adhesion (depending on the length and depth of the crack which we don't know without seeing it) you can over reduce the the primer and give it a better chance of flowing into the cracks, but then you come back to the original problem of solvents being trapped (similar situation to W&GR only in this case you can't blow them dry) in the cracks making the crack line reappear later. When paint with defects aren't prepped in a way that entirely removes the defect, these types of situations arise and people must make a judgement call. How wide are the cracks, How long are the cracks, will epoxy flow into the cracks or bridge the crack, putty may not get into the crack or maybe it will, how thick is the epoxy and what happens if I over reduce it to get it to flow into the cracks, will it come back to haunt the Camaro down the road? These are all valid questions that could have easily been solved by removing the questionable substrate prior to applying a primer. But that's where we are now.

I also agree that we don't know the properties of Summit"s products which makes giving advice even more difficult, all we can do is draw from past experience and hope the problem doesn't haunt in the future.

I very much appreciate the fact that you never said "this is what I've done" suggest a repair and continue with '"and I've never had a problem". That kind of advice scares the crap out of me when I know that any solution to situations like this are not without chances of a consequence.

I suggested putty as a bridge and attempting to force the putty into the crack rather than filling it with epoxy because I don't have the part in front of me, I weighed out the possibility of failure and made a judgement call. I felt the chances of flowing primer into a tight crack would bridge the crack without penetrating leaving air trapped was a great possibility and creating a problem, over reducing the epoxy so it flows into the crack has the potential to trap solvents, creating another problem, filling the cracks as pest as possible by forcing the material into the cracks and then applying the epoxy primer, in my thinking, would minimize a problem that is still potentially there. When it comes to bridging a problem with primer or filling a problem like this with putty is not the proper way to eliminate the problem, all we can do now is do our best to minimize the the potential of failure in the finished product...Wouldn't you agree?

I do understand that bumper covers with cracks are a PITA and the best solution is to strip them which also is a PITA. So today we are faced with how to find a solution that hopefully fixes a PITA.

Wouldn't you agree Dead?

Ray
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  #82 (permalink)  
Old 11-20-2012, 08:00 PM
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Thanks guys. Interesting read. I'm going to try to fill the cracks with my poly glaze and see what happens.

Blocked out the passenger side tonight with 320. The quarters and fenders on this thing are a piece of cake. BIG door though!! Looks great so far, I used a guide coat and only have a couple low spots to glaze.

My plan is to block the whole thing out with 320, fix the nose and the low spots, then 2 more coats of epoxy. After that 600 and paint? Or do I need to do 400 and then 600? What about just some 500? This is where I get confused.

BTW, I really like the Summit epoxy, I used it on my Nova and really liked it and thats why I bought it again...You guys should try some sometime and see what you think.

Andy
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  #83 (permalink)  
Old 11-20-2012, 08:46 PM
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Hey Andy, 400 by itself is generally enough for solvent based B/C, The only problem is that grits are different in North America than they are in Europe and if I remember correctly you said the sand paper came from Germany....If you go 500 I'm sure you'll be good to go.

Are you re-priming the whole car or just the repaired areas?
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  #84 (permalink)  
Old 11-20-2012, 09:19 PM
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I thought I would just reprime the whole car... I still have a half gallon of the epoxy (1 gallon when mixed), might as well use it all.

Ill get some 500 wet or dry and go with that .

The sanding I did tonight was 320 wet, the epoxy is still kinda green, I guess because of the cool temps and it wanted to clog my dry paper quickly. Did great with the 320 wet though.

THANKS for all the pointers on this Ray.

OH, ordered up a spray gun tonight... its still a beginner model, but I'm climbing the quality ladder slowly. A friend on my Nova site recommended it and he has an Iwata also, he says it sprays just as good LINK >>>

http://www.johnsonautobodysupply.com...Gun-1-4mm.html
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Old 11-20-2012, 09:35 PM
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Your more than welcome, I probably want this job to turn out well for you almost as much as you do.

If your going to re-prime the whole car, you can use a coarser grit than 320, like 220 or 240...make the job faster, prime over your body work areas first, then the whole car, this way if you are a little low on the body work you have more primer to work with.

I took a look at the gun, sorry, I've never heard of it but, that doesn't mean it's not going to do a good job for you....Let me know how it sprays.

Ray
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  #86 (permalink)  
Old 11-20-2012, 09:43 PM
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Ray,

would 180 be to coarse?? I have an entire roll of that on hand. Thanks for the tip about hitting the repair spots with extra primer first.

Andy
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Old 11-20-2012, 09:47 PM
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Just a quick note as I was rereading your post, I've never seen 500 wet before, I goes from 400 to 600, but I'm in Canada and things may be different in the US, if they don't have 500 wet, get 600. 400 wet seems to be more aggressive than dry and base coat goes on thin. I like wet paper for my final sand it's messier on the floor but leaves a better finish on the car, easier to see any imperfections in the reflection as well.

Ray
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Old 11-20-2012, 10:09 PM
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As far as 180 goes (I was really hoping you weren't going to ask) would be OK, go over it with 320 again, just to knock the high points of the 180 foot print off. The reason I cringe at 180 is I don't know how well your epoxy fills and 180 leaves some deep scratches and when primer fills these scratches it has a tendency to shrink in time and the scratches show up sometimes 4 to 6 months down the road. Also allow extra flash time before giving it the second coat to get as much solvent out of the primer as possible. This will minimize chances of shrinking later. I know your primer is 1 part primer 1 part catalyst but you still have solvents in the product.

Make sure you go over it again with 320, it's a bigger jump in grit than I like but your re-priming so all should be good.

Ray
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Old 11-20-2012, 10:14 PM
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I'll just do 320 then... I'm not in a big hurry (it might seem like it...lol), I'm not going to prime till the new gun comes, that way I get to test it out!!

I have plenty to keep me busy till then

Thanks for all the great tips... this thing is going to turn out GREAT, I can feel it
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Old 11-20-2012, 10:26 PM
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That's the safest bet, if I knew more about the primer you where using I'd feel more comfortable telling to use the 180 and re-prime, and, like you say, your not in a hurry and quality is what you want.

And all I want is to give you the best information I can so you can get the finish you want.
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