i have sanded most of my body work down to the plastic or close to it to get rid of imperfications.

i am down to 220 grit at the moment as i will be using duponts nason primer and then there base/clear coat urathane.

i was just wondering if i should go to 320 then prime?....or will this primer fill any scratches?

i am hoping to paint tomorrow or the next day.

I just did some work on mine and I sanded with 320 before painting. Is it a finish primer or a filler? That would be the best way to decide. I think that 320 should be sufficiant before priming....

I read that 500 wet/400 dry was the recommended grit before primer. I did mine with 500 wet.

320 will be better than needed for primer/filler. In fact I like to use no finer than 220 for primer filler, as the primer has something to grab onto. If you're using spraycan primer, I would go finer like 400. I hate that spraycan primer. Then of course go 400 before paint.

How deep are you all sanding.......

320... on fiberglass/plastic?

better to cut slower with finner grit than cut scratches.

400 is coarse paper on this stuff, even when used wet. The substrate is only a little harder than the paint. Depending on the paint/panel you are working it may even be softer.

If you have scratches AND if you used a sandable primer AND if the primer fills the scratches... (A stupid way to do it as far as I'm concerned.) scuff the primer with something really fine like 0000 or finer steel wool before even thinking about paint.

Fiero isn't like painting a metal car. Anyone that treats it like such is asking for a major headache.

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11-Sept-01, The day the world as we knew it ended.

I would never put anything less than 400 on my car before or after primer. If you want a pristine paint job and are just smoothing the old finish before you prime and paint, 400 is good. Any less and the sanding scratches will eventually show through the new paint. If you scuffed it down with 220, you have a lot of sanding to do. Primer will fill some of the scratches but as mentioned above, that's not really a good way to do it.
With the high gloss of the urethane paint system you're using you want the finish smooth before you apply the paint but with enough "tooth" for the paint to stick. I would also suggest a coat of sealer before you paint it. 400 before the primer and 500 before you paint should render a smooth, tight finish.

Don

anything finer than #180 is ok for panels that are going to be primered. I try to use 240-320 myself. Primer is sanded with at least #400. Panels that are not primered have to also be sanded with at least #400.

thanks everyone for their input so far.

the reason i had to use such a coarse grit is that i had to cut through many coats of bad paint..the type that clogs your sandpaper with only 4-5 strokes, really bad clear coat that was cracked and faded, not to mention cracks in the paint that was on the front a rear bumpers. you can see the pics on my other thread https://www.fiero.nl/forum/Forum1/HTML/021712.html
this has taken me a long time up to this point and i want to start primeing some of my panels today, maybe even get them painted too.

You should have asked here first to save lots of sandpaper WET sanding nearly eliminates the clogging problem. Wet #220 would have cut it off reasonably quick.

Ya, I guess I was giving instructions for painting a metal car rather than a plastic or fiberglass one. I wouldn't go more coarse than 320 with plastic. If you have several layers of paint, you could cautiously try stripper or cautiously try 220. I'm painting my truck now, so I'm using 60 on what I call the, "nuclear-proof pinstriping." Man, after MEK and hours of scrubbing it's finally gone, but then there's the factory paint seam where they hide the joining of the 2-tone paint schemes. It leaves a big bump right there, and I'm going with straight white so I neen to knock all that down. But ya, go as everyone else told you and go 320-400 wet.

if your preping to primer it i would use min. 500 grit . if the primer is also by dupont its either very prime a.k.a etch primer, or euro prime a.k.a fill primer. i used dupont paint and primer for 5 1/2 years. mainly dupont chroma premier and chroma one. if you are useing one of these two and have questions email me i will gladly help. i have also used ppg paint . and i curently use martin senior at the body shop i work at now. good luck . hope it turns out nice

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go fast or go home
or just drive it like you stole it

email cwandall@yahoo.com

roger..if i could have found 220 wet here i would have used it for sure!!

I remember we used oven cleaner to lift stips and decals but I don't know if that would work on some of the newer factory stipes/decals. They've made those adhesives really tough over the years. 3M has products made just for this job. I'm not sure if you can use them on plastic or fiberglass panels tho.

Layers of paint are never fun. You've got to be very carefull trying a stripper on a plastic. Test a small spot on the back of whatever panel first. If you don't you could eat the panel as well as the paint.

Coarse steel wool might work better than sand paper on heavy stuff... it's worth trying. You want the heavy stuff. Somthing like what they use to strip wax of comercial floors. There are also some really coarse scotch brite type products that might work.

You have to do whatever you have to do to work out those scratches now. Anything you don't get now Will show thru the paint later.

If you have deep scratches you're better to use a scratch filler than just flood with primer. It's more work/cost but it will end up much better.

[This message has been edited by theogre (edited 10-19-2002).]

sometimes pits or scratches are hard to see in primer. A little trick to help you spot defects is after you primer the whole thing in say red oxide, take a spray can of white and mist it very finely over the primer. Then when you sand the primer down, all the low spots, chips, scratches, etc will still have white in them. You just keep blocking down the primer till all the white specs are gone. They do make a special stuff to do this, but cheap ole $1 can of spray paint does the same thing.

I work in a heavy truck body shop (KW) and I have PAINTED after sanding with 150 and you could NOT see were it has been sanded. 320 looks absolutely great before painting. All we work on is fiberglass and plastic and I have seen no problems.

quote Originally posted by fierodustin_86: I work in a heavy truck body shop (KW) and I have PAINTED after sanding with 150 and you could NOT see were it has been sanded. 320 looks absolutely great before painting. All we work on is fiberglass and plastic and I have seen no problems.

Absolutely, especially if you're using a think PPG polyurethane that is maybe a little under thinned, or on a horizontal surface that will afford you to spray the last coat a little thicker without running. Laquers, not that I've used them, would be less foegiving in regard to the scratches.

well guys i have just primed a few pieces and i can still see a bunch of tiny sanding scratches...how do i get rid of these pesky little buggers??

I like wet-sanding. Some people dont, but I think its best. Go get some guide-coat and 3M wet-dry sandpaper in 500 grit. Guide coat, as mentioned above, just adds a dusting of light color to the very top layer, so any imperfections show up as darker (lines for scratches etc). Then run a tiny trickly of water over the surface and sand it out with the waterproof sandpaper until no imperfections show. (I just paid 90 cents per sheet for my current project. But its well worth it) Finish sanding is a bit of an art-- you've got to be careful not to leave grooves in the surface from the sandpaper. If you're using a sanding block, be careful that as you push the block forward, keep the angle of the block at about 25-30 degrees to the direction of travel. That prevents the hard edge of the block from digging down as you sand... the angle makes it so the corners of the block sort of taper off. Of course, some places are not blockable. Use your fingers on areas like inside the light recesses in the bumpers etc, but be sure to never follow the same stroke twice. Mix it up to avoid uneven sanding. Elsewhere on rounded surfaces you can use the part of your palm thats sorta fat (base of thumb area)... just be sure that the edge of the sandpaper doesnt get pushed into the paint. Sandpaper edges should recieve no pressure at all to avoid grooves.

People who dry-sand can use less fine grit, since the sandpaper tends to clog up with dust, and indeed 320 might work just fine in that case. I just notice that base-clear jobs are rather unforgiving in that basecoat never seems to fill scratches very well, even if you give it a nice fat layer of sealer first.

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87 Quad 4 HO convertible

If you see the scratches in the primer, thats fine. thats what the primers for, filling them. when you sand that primer and recoat it, youll see most or all of them disappear. You just keep repriming and sanding till there all gone.

well roger and the rest of you guys ..thank you very much for the tips...i did a little wet sanding with 400 grit and when i applied the next coat of primer, poof!! all the scratches had disappeared!

if you want to see my handy work on what the out come was. check my on going thread at:
https://www.fiero.nl/forum/Forum1/HTML/021712.html

once a again a big thanks goes out to my PFF friends.

ernie.

[This message has been edited by gt boy (edited 10-21-2002).]