plastic bumper prep

[E30_(1st Musk)_]

i just picked up a plastic bumper. but paint is no good. i am going to use Duplicolor gloss black/clear coat...any tips...sanding?etching primer?

[ck_taft325is]

60 grit to start it off. Fill any deeper scratches with a feather finsh (a few are mentioned in various threads here), finish with 320 (60 - 120 - 320). Sandable primer (I always used an automotive sandable primer from Home Depot, Lowe's etc etc).

I've never used Duplicolor per se, so I can't help you there. Biggest thing is to make it all straight with a decent body feather finish of sorts, prime and sand (with a palm block, not your hand).

Good luck! Post some pictures up of your progress and/or finish product ;)

[Eric Giles]

I generally agree with what CK says above, however unless you have very deep scratches or gouges in the plastic, I would not start out with 60 grit paper. Start with 180 grit, fill in any imperfections with Evercoat body filler, block sand again with 180 till level. Then spray a filler primer and block sand with 320 grit. To make sure it is as smooth as possible, do a final wetsand with 600 grit and then paint.

I am by no means a body/paint professional, but I have a good friend that is and I have helped him with a number of jobs-including my E30 in my sig-and this is the process that he had me do on my bumpers.

[E30_(1st Musk)_]

thanks guys, i just re-checked this morning. and the bumper dosent have any deep scratches or cracks..it seems like they repainted it. and whatever they used is just flaking off...should i still start with 60 or 180 grit?

[Eric Giles]

thanks guys, i just re-checked this morning. and the bumper dosent have any deep scratches or cracks..it seems like they repainted it. and whatever they used is just flaking off...should i still start with 60 or 180 grit?

DEFINITELY start with 180 grit as the lowest-I should have said that even with deep gouges 80 grit is the absolute lowest you want to go. Anything lower will leave scratches that if not properly smoothed and filled out will show up in the final paint. You might even just want to try 320 as long as it will remove all of the old repaint and properly scuffs up the original.

[E30_(1st Musk)_]

so i should just start with 180. and stay at 180?

[Eric Giles]

As in my previous post, start with 180, then spray filler primer. Then block sand with 320, and then wetsand with 600 grit before painting. If you don't do the 600 grit wetsanding, you will see the 320 grit fine scratches in your paint.

All of the sanding should be done with a sanding block to maintain flatness.

[E30_(1st Musk)_]

alright cool. i just wrote all that stuff down..
thanx man

[E30_(1st Musk)_]

ok. i have both the bumpers now!
i have the sand paper. but my questoins is.
if i am able to get my hand on a power sander. can i do the 180 and 320 with that?
and what can i use on the inpact strips. im going to try sem black. but can i fine sand them?

[MattM]

by power i am assuming you mean a orbital sander(round) you can do the 180 with this, but unless you are taking heavy material off there isnt really a point, Also, the bumper is so uneven you wouldnt save yourself mush time at all, and after the sandable primer you should ONLY use a block and straight line sanding.. if you have air then a panel sander works, but even that is a little bulky for the small surface areas of the bumpers...

i did my entire car with nothing more then a block, its not that bad, the only times i used an orbital was when i needed to remove a lot of materal like getting down to bare metal or filler slop(no im not a pro and have done afew mess ups with the stuff).... the rest i did with block and powered panel sander.

[E30_(1st Musk)_]

oh i understand you. ill just use the block sander. to make sure.
Do you know what i should do to repaint the bumper/impact strips? the black is faded

[MaloventEvil]

DEFINITELY start with 180 grit as the lowest-I should have said that even with deep gouges 80 grit is the absolute lowest you want to go. Anything lower will leave scratches that if not properly smoothed and filled out will show up in the final paint. You might even just want to try 320 as long as it will remove all of the old repaint and properly scuffs up the original.

am i not supposed to sand between basecoats?

so is this the order:

- fill and sand
- primer (1 coat)?
- sand with 600 grit
- basecoat (# coats?)
(no sanding)
- clear coat?
(no sanding)?

[genocide98]

the only time you want to use 80 grit is if you're shaping bondo...

Anything else and it can leave deep scratches which might be hard to get out without making your paint look wavy.

to take deep scratches out you either use filler primer or a special kind of bondo, depending on the depth and location. you only really wanna use bondo on surfaces that are relatively flat and allow you to use a long sanding block to make sure you keep the original radius of the body panels.

the process should be

strip everything possible off the piece you paint
sand w/ 220~ grit until everything is scuffed.
depending on condition, use bondo or filler primer on piece
sand w/ 80 then 220, or just 220 again depending on what you use.

Some people use a harder primer at this point, but usually if you aren't going to keep it unpainted you should be fine.

base coat
sand w/ high grit
base coat
wet sand w/ high grit
clear
possibly wet sand (if there are any imperfections)
clear
clear

you just have to make sure you do your sanding within a specific window of time. If you sand too early paint will be soft and you'll screw it up. If you wait too long between coats the layers might not react very well together and they might give you issues such as bubbling, orange peel, flaking off, etc.

you usually only wet sand the base coat and once in the clear coat to make sure everything is smooth. If you have everything nice and ready you might be able to skip the step.

If you make any larger mistakes (what we called tragedies at work) you usually gotta start over from the primer/bondo stage, or at least on that specific body piece.

EDIT:

I didn't see this, but if you're doing something small like a bumper, valence, mirrors, etc you DO NOT want to use a power sander. It wont really make it any faster or easier, and in reality it'll probably take off way more than you want. use a nice sanding block that spans all the way across the bumper. If you don't have a sanding block you can use a block of wood or something, but I prefer a nice FIRM foam block.

[E30_(1st Musk)_]

the only time you want to use 80 grit is if you're shaping bondo...

Anything else and it can leave deep scratches which might be hard to get out without making your paint look wavy.

to take deep scratches out you either use filler primer or a special kind of bondo, depending on the depth and location. you only really wanna use bondo on surfaces that are relatively flat and allow you to use a long sanding block to make sure you keep the original radius of the body panels.

the process should be

strip everything possible off the piece you paint
sand w/ 220~ grit until everything is scuffed.
depending on condition, use bondo or filler primer on piece
sand w/ 80 then 220, or just 220 again depending on what you use.

Some people use a harder primer at this point, but usually if you aren't going to keep it unpainted you should be fine.

base coat
sand w/ high grit
base coat
wet sand w/ high grit
clear
possibly wet sand (if there are any imperfections)
clear
clear

you just have to make sure you do your sanding within a specific window of time. If you sand too early paint will be soft and you'll screw it up. If you wait too long between coats the layers might not react very well together and they might give you issues such as bubbling, orange peel, flaking off, etc.

you usually only wet sand the base coat and once in the clear coat to make sure everything is smooth. If you have everything nice and ready you might be able to skip the step.

If you make any larger mistakes (what we called tragedies at work) you usually gotta start over from the primer/bondo stage, or at least on that specific body piece.

EDIT:

I didn't see this, but if you're doing something small like a bumper, valence, mirrors, etc you DO NOT want to use a power sander. It wont really make it any faster or easier, and in reality it'll probably take off way more than you want. use a nice sanding block that spans all the way across the bumper. If you don't have a sanding block you can use a block of wood or something, but I prefer a nice FIRM foam block.

perfect.
The paint on one of them is bubbled and i can take off with my own two fingers...
the other has a few deep scratches..
Since i am using a duplicolor can..
do i absolutely have to sand between coats? cuz the can has a gloss to it. and then i was going to buy the duplicolor clear coat also...

if im correct. you said i can use the filler primer on single pieces rite? i dont have to spray the entire bumper

[MattM]

if im correct. you said i can use the filler primer on single pieces rite? i dont have to spray the entire bumper

yes you can, but i can tell you right now that 30 year old paint wont look the same as 30 minute old paint. you will see a line where you didnt apply new paint. If you are doing any repairing to the bumper you are best off to spray the entire thing.

the best paint for the trim (IMO) is SEM black trim paint. it is designed for plastic and matches the factory color very well(you arent stuck painting every peice of black on your car afterwards so it looks right)

Im currently working on my bumpers too, retrofitting to fit an early model car... quite the task