What is the recommended Grit for blocking

[Scott Marzahl]

I've had several different recommendations as to what grit sandpaper I should use for blocking replacement panels, repairs and the bare fiberglass body prior to spraying a polyester sealer. Is 80 grit the preferred or something finer like 150?

Thanks.

[Dennis C.]

Re: What is the recommended Grit for blocking

Scott - My opinion. 80 is a little rough. What you don't want is what they call "sand scratch swelling"... Often, with a repair, you can start with 40, switch to 80 and then finish with 150, 180 or 220. Usually, before I would apply final color coat on a car (lacquer), I'd recommend 400 grit. Enamels are more forgiving as they have more of a "filling" quality. Best, Dennis

[Scott Marzahl]

What do you use prior to Mortons 100?

Dennis, what surface do you want for the Mortons or Slicksand to adhere to?

[Dennis C.]

Re: What do you use prior to Mortons 100?

Scott - My experience is with Morton's Eliminator. I would apply it over bare glass and body repairs. That stuff will fill 40 grit sand scratch repairs. However, the way I approached things was with 2 applictions of Mortons. First (2) coats to fill the major repairs and sanding with 150 or so. Second application sanded with 400 when applying lacquer color coat. All these are wet sand. The stuff is bullet proof. It is a filler, primer, sealer. If you experience a major setback, wash it off with lacquer thinner. Won't bother the Mortens... Hope I've filled in a couple blanks. Dennis

[Bill W.]

Re: What do you use prior to Mortons 100?

The finished "bare " body should be block sanded with 220 wet, hand sanded with 400 wet, primed & blocked with 400 wet, & sealed. If you need to sand your sealer use 600 wet. Use the same brand of primer ,sealer,& paint DONT MIX BRANDS . Why fill the scratches when you can sand them out ? Dennis is right if scratches are not there they cant shrink. Also the less material you have on your car the longer you can expect it to last....Bill

[Scott Marzahl]

Wet sanding bare glass

Bill, do mean to wet sand bare fiberglas, maybe I am not understanding correctly. My car is down to bare grey glass, previous owner had it blasted.
I am blocking the rear deck lid with 40 in places, followed by 80 and I think next 150 before I shoot some slicksand or Mortons on it. I wil be installing a new front end one of these months so I'm getting as much ready as possible now.

[Wayne P.]

Re: Wet sanding bare glass

Way too course for bare glass!

[Bill W.]

Re: Wet sanding bare glass

Yes, wet sand the bare glass with 220 wet.. Why fill all those deep scratches????Again dont mix brands of primer,sealer and paint!!!!Unless your going to paint with mortons or slicksand dont use it.All the major paint companys have their own 2 part urathane primers.

[Scott Marzahl]

Re: Wet sanding bare glass

Bill,
I thought getting water on bare glass was a no no because fiberglass would absorb the water. Granted, I understand wet sanding sure is easier. I would imagine it would take a few days, weeks to dry out depending upon the temperature.

Am I correct in my assumption?

Thanks,
Scott

[Bill W.]

Re: Wet sanding bare glass

Yes & no .yes it does need time to dry . On a 60 + degree day with a little sun it will dry in a couple hours or less.If you used stripper on your car I hope you washed it with lots of hot soapy water. The water will bring all the dirt and grime out of the glass.

[Terry F.]

Re: Wet sanding bare glass

You will get a lot of different opinions on what to do and not to do to bear fiberglass. I would avoid trying to flat sand it but it sounds like a lot do it anyway. I would use a gelcoat on it and flat sand it even though it is hard to flat sand or I would use a primer that can be used for flat sanding. Not an expert, just my opinion.

True, when people analize the contents of the blisters that form under the corvette paint, it is usually mostly water. I read that somewhere. Fiberglass is like a sponge. Very tough surface to paint if you are not an expert in my opinion.

Terry

[Dave Suesz]

Just remember to

let it get VERY dry before you re- gelcoat it, or you'll trap water that will steam its way out later.