How long to wait to sand run in clear

bill3337

bill3337

Member
I had a couple small runs in the clear on the underside of my '37 Ford body. I waited about 36 hours then skimmed them with polyester and sanded them out, but it seems the center of the drip hadn't cured totally and has tiny holes etc and show's a bit of white. Ia this from solvent trapped in the run? In this case I'll just touch them up as they are under the car and will be covered by the frame, but obviously I sanded them too soon. Should I be knocking the shine off the run in 24 hours or so, to let the solvents out, then wait for a period of time before sanding them right out? I don't have UV lights or anything, so how long should I wait before sanding out any runs or sags? Thanks, Bill
 
the thicker the run the longer the cure. If you don't have a heat lamp just let it set long enough so it is sandable-usually 12hrs/overnight is plenty, then carefully block sand the majority of the run off and then allow it to cure some more-you want that run to cure, harden, shrink before you final sand it. I've never glazed a run but I would bet there is a chance the clear could pull in some solvent and slow the cure down if it is fresh?
 
We like to sand them part way down with 800 than sun-cure it, otherwise it will show like Bob says. The thickest parts of the run will shrink the most, since they are trapping the most solvent.
 
A little late for this time, but a trick I learned from a crappy little small town paintshop when I was a young kid was to use a piece of masking tape on a fresh paint run before it dries. Hold a small length of tape with both hands & lower onto the dip, the adhesive will catch most of it. you may make a pebble finish where ever the tape hits, but it will be smoother than a run.. If you check things over while you still have mixed paint, you can do this & lightly hit a little more spray over the spot.
 
That's an interesting concept! I'll try that if I get one that's in an inconspicuous place. That should resolve the issue of the center of the drip taking so long to cure and shrink. Anyone know a reason why not to try this? Thanks, Bill
 
if your hell bent on working on it while fresh use a small brush to gently pull the excess off. tape can leave you with a thin spot. i use a dagger brush but usually just leave it till cured. then i use 2 in tape on it ..
 
Hi Shine,

The reason I was considering this is that I had a small run on the underside of the body, about 2" long 3/16" or so wide with a little glob of clear at the end of the run. I sanded it out, but had only waited about 48 hours after clearing. The run seemed sort of porous as if there was trapped solvents there and once sanded flush, leaves a ghost line of "pinholes" where the run was. It was worst where the run was thickest.
 
yeah the solvents get trapped. use a dagger brush or qtip to get the drop while it's wet .
 
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