Low spots after blocking

S

Skycab

Promoted Users
I'm really confused. I sanded my car to bare metal, applied "Picklex 20" which is a rust blocker/converter (before I learned of SPI) then sprayed the car with a good epoxy primer. Got a LOT of opinions on using that product and probable future de-lamination issues. So I talked with Barry who advised to once again strip the car to bare metal, apply OSPHO and start over. I did. So after a couple of weeks with the re-spray of epoxy, I got SPI's Turbo 2K primer. I sprayed the doors, boot lid and bonnet and the 2K primer is really nice. However, in block sanding, I did see a few very minor low spots that I want to use Upol glaze putty on. I also sand through to bare metal on a couple of small spots.

I'm confused as to whether I have to use EPOXY primer again on the bare spots and do I have to sand off the 2K primer in order to use the glaze putty on the low spots? I've read that the putty won't stick over 2K primer? I know this is elementary to you guys that do this a lot, but this is my first paint job on a car (I have a professional painter who will shoot the BC/CC for me) so your advice is really needed and much appreciated. The car has NO straight panels, meaning it is all curves. It's a 1951 Jaguar XK 120 OTS. A real bag of fun to sand.
 
You can glaze over the turbo primer. If the low spots aren't sanded run over them with some 180 grit prior to glazing the spots. Best practice is to spot the bare areas with epoxy before spraying another round of turbo primer
 
Jimthecarguy said:
You can glaze over the turbo primer. If the low spots aren't sanded run over them with some 180 grit prior to glazing the spots. Best practice is to spot the bare areas with epoxy before spraying another round of turbo primer
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That pretty much sums it up, good suggestions.
 
Great! Thanks very much for the quick response. I thought it was going to be a real mess but that's not so bad.
 
Yeah, the knowledge of the guys on this forum is really something. They all give advice. Barry was great and obviously knows a little about painting.
 
Ideally you don't want to glaze over urethane primer. It's done a lot but it's not ideal. Glaze can swell urethane primer and cause mapping in subsequent topcoats. If you have to do it, you don't want to do it on fresh urethane primer. Get it out in the sun. Or get some heat on it for a while. Where it will show is down the road after you have painted and everything has gassed out. Not always but it does happen. Ideally you would only apply it over cured OEM finishes, over filler, or epoxy.
 
Uh oh. Well that may put me back to square one. So you're saying that for the low spots, I have to sand back down to the epoxy primer, which means undoubtedly through to bare metal, THEN epoxy the bare spots, THEN apply the glaze putty, THEN re-spray the 2K primer? YIKES!! But I'll do it.
 
While we're at it, what do you all recommend as far as sanding? After I deal with the low spots and apply the final coat of 2K SPI high build primer, what should I sand with to make sure there are no issues with scratches down the road? I also plan on letting the car breathe for a couple of months before BC/CC and I know I'll have to use a red scotch-brite over the whole thing before painting, right?
 
Well, in do a lot of reading before starting this project, I read article after article saying that epoxy primer is NOT sandable. I believed it until I sprayed the car the first time with LIMCO epoxy and after a couple of days, decided to try and lightly block sand to find any low spots. I found that it sanded great! Then more reading lead me to believe you need to spray 2K primer, block, spray again, block and repeat until you have the straightest panels possible. So that's what I planned on doing! Everyone has a different way of doing it. So now because I've already bought the 2K SPI turbo high build, I'll stick to the spray. block, spray plan. Just looking for the grits. I sanded the boot lid today with 180, then 320 and although very smooth, I can still see the 320 scratches. Am I doing that wrong too??
 
In terms of grits and scratches, an easy solution is to do all your blocking until you are happy with it, then shoot a reduced coat of 2K over it all, which will fill in sanding scratches, and then smooth it out with 400 grit and proceed to sealer or base, whichever is your plan.
 
As stated I like to block sand the epoxy. While doing so the low spots will show as shiny areas. If I have access to the underside, I will gently tap those areas up using a body hammer. You can run the sanding block over the area to check your progress.

If I don't have access to the back side and the dent is deep, I use a stud puller. The goal being to keep filler use to a minimum.

Once that's done the 2k build primer should handle anything else fairly easily.
 
Skycab said:
Ok, but what grits do I use? 180, then 220, then 320 then final coat and 400?
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It's not a formula. Use the highest grit (smaller scratches) possible that will cut it flat.
I like 220 to start with.
Are you using a guide coat of some type? That will help immensely.
 
Yeah, the turbo SPI 2K primer is black (car will be British dark green) so I have a white powder guide coat. I just blocked out the boot lid with 320 and it's smooth but you can see the fine scratches.
 
Skycab said:
Uh oh. Well that may put me back to square one. So you're saying that for the low spots, I have to sand back down to the epoxy primer, which means undoubtedly through to bare metal, THEN epoxy the bare spots, THEN apply the glaze putty, THEN re-spray the 2K primer? YIKES!! But I'll do it.
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No I'm not saying that.

How low is low? If it's is ridiculously low then you may have a problem in that spot. But if the lows feel pretty minor it's normal.

Sometimes the best course it to just re-prime it. Try this first. One coat of epoxy on the bare metal spots only. Then 3-4 more coats of 2K primer. If your lows are minor it will fill them.
 
Yeah, that worked on the boot lid, no glaze needed. The rest of the car will have some low spots on the large side panels I'm sure. You can't see them until you block them. None need a hammer but for the ones that need a skim coat I just wanted to know how to deal with that. Thanks.
 
Make sure you wait the appropriate time after the one coat of epoxy before 2K. 2 coats is 24 hours so 18 hours or so for one coat would be safe. Probably quicker, check with Barry on the Tech Line. He will let you know how soon after the epoxy that you can re-coat with 2K
 
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