Body filler/poly primer question

NextGen Classics

Floor sweeper
Question... Are you guys sanding your filler/poly finer than 80 grit before applying more filler? I only do when it is my last application of filler or poly primer,then go to 180.
I thought the next application of filler would bite in better than a finer tooth but maybe I am overthinking it. Never stop learning........... Thanks
 

NextGen Classics

Floor sweeper
I have read on this forum that some of you do in fact sand their filler with a finer grit and I was wondering why? It would be more blocking,is it necessary? What does it accomplish? Not bashing by any means and if it is a smart thing to do I am all for it.
 

crashtech

Combo Man
I never prime over 80 except for metal, reason being is I've seen too many cases where material shrinks into the scratches. Of course good materials, technique, and long dry times that are used in restoration mostly make this a non issue, but for me it's just a habit. Also I think my hand feel becomes more accurate when the surface is smoother. Yet another reason is that I think body lines can be better shaped by going out to a finer grit, 80 is really rough on tight curves, which is really what most body lines are, they're not perfectly sharp. So with 80 you can block them a bit overly sharp to make sure they are straight, then carefully dull them down with finer grits until there's some metal showing. That's just how I like to do things, it gets me good results.
 

NextGen Classics

Floor sweeper
I guess my question should have been, does filler or poly primer shrink back into previous 80 grit scratches? Not urethane primer. Thanks
 

NextGen Classics

Floor sweeper
I never prime over 80 except for metal, reason being is I've seen too many cases where material shrinks into the scratches. Of course good materials, technique, and long dry times that are used in restoration mostly make this a non issue, but for me it's just a habit. Also I think my hand feel becomes more accurate when the surface is smoother. Yet another reason is that I think body lines can be better shaped by going out to a finer grit, 80 is really rough on tight curves, which is really what most body lines are, they're not perfectly sharp. So with 80 you can block them a bit overly sharp to make sure they are straight, then carefully dull them down with finer grits until there's some metal showing. That's just how I like to do things, it gets me good results.
What about fiberglass? Reason I asked is I just blocked a glass hood I sprayed with epoxy then slicksand. I hit gelcoat in a couple areas. Should I epoxy those areas before applying more slicksand?
 

crashtech

Combo Man
To stay consistent with your procedure, you would of course epoxy the gelcoat, though I personally do not believe it is necessary, since gelcoat and poly primer are closely related. Epoxy is more of a recommendation for bare, old fiberglass where the resin is beginning to deteriorate.
 
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