Results 1 to 8 of 8

Thread: Advice on prep (sanding and priming and masking) before painting -- Help appreciated

  1. #1
    Join Date
    Feb 2005
    Posts
    115

    Default Advice on prep (sanding and priming and masking) before painting -- Help appreciated

    Has anyone ever done their own sanding and priming before taking their car to be painted at a shop?

    Is it possible to damage my car's body with sandpaper?
    What grit sandpaper should I use to ensure no damage is done?
    How will I know I've sanded far enough?
    Does sanding to bare metal offer benefits?
    Is it possible to sand past bare metal and permanently **** up?
    If I'm changing color, do I need to sand down to bare metal?
    If I sand to bare metal should I use a dual action air sander or a hand sander? I mean is it possible that using a machine sander will take me down too far?
    For masking, is a single layer of automotive painter's tape enough for small areas and what should I use to mask larger areas, plastic trash bags?
    Is applying your own primer a simple process? I mean: Is there a chance to **** up and have to restart?

    Thanks for anyone with the experience.

  2. #2
    Join Date
    Dec 2003
    Location
    Eastern Tennessee USi
    Posts
    14,689

    Default

    Whoaaa... sounds like you have good intentions but are not sure WTF you are doing. I have painted many cars and trucks over the years so I will just give you my look at it and my oppinions. The only way you will damage the new finish is using too course of paper...sanding scratches look like **** and you cant hide that.

    I would use a DA sander with 600 grit to take it down past the clear, if you use finer paper than the new paint wont stick good enough.

    I wouldnt recommend taking it to bare metal unless you are into that kind of work, if you do then you will need to prime it with the appropriate material so it doesnt react with the current paint that you miss and also needs to work with whatever paint the shop will be using. You should call them for their oppinion on what kind of primer to use. About the only benefit of this is you have less chance of the paint cracking in the long term.

    Use newspaper for the windows and stuff, I assume you are going to tow the car to the paint shop, if not you will need a periscope

    Good luck, take your time and it will turn out great!




    Is it possible to sand past bare metal and permanently **** up?
    If I'm changing color, do I need to sand down to bare metal?
    If I sand to bare metal should I use a dual action air sander or a hand sander? I mean is it possible that using a machine sander will take me down too far?
    For masking, is a single layer of automotive painter's tape enough for small areas and what should I use to mask larger areas, plastic trash bags?
    Is applying your own primer a simple process? I mean: Is there a chance to **** up and have to restart?

    Thanks for anyone with the experience.[/quote]
    95 E34 530I V2.31
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  3. #3
    Join Date
    Feb 2005
    Posts
    115

    Default

    Quote Originally Posted by 632 Regal
    Whoaaa... sounds like you have good intentions but are not sure WTF you are doing. I have painted many cars and trucks over the years so I will just give you my look at it and my oppinions. The only way you will damage the new finish is using too course of paper...sanding scratches look like **** and you cant hide that.

    I would use a DA sander with 600 grit to take it down past the clear, if you use finer paper than the new paint wont stick good enough.

    I wouldnt recommend taking it to bare metal unless you are into that kind of work, if you do then you will need to prime it with the appropriate material so it doesnt react with the current paint that you miss and also needs to work with whatever paint the shop will be using. You should call them for their oppinion on what kind of primer to use. About the only benefit of this is you have less chance of the paint cracking in the long term.

    Use newspaper for the windows and stuff, I assume you are going to tow the car to the paint shop, if not you will need a periscope

    Good luck, take your time and it will turn out great!



    Is it possible to sand past bare metal and permanently **** up?
    If I'm changing color, do I need to sand down to bare metal?
    If I sand to bare metal should I use a dual action air sander or a hand sander? I mean is it possible that using a machine sander will take me down too far?
    For masking, is a single layer of automotive painter's tape enough for small areas and what should I use to mask larger areas, plastic trash bags?
    Is applying your own primer a simple process? I mean: Is there a chance to **** up and have to restart?

    Thanks for anyone with the experience.
    Actually I planned on masking the windows when I got there I was not sure if newspaper would be proper to use because I imagined it being too thin to really protect. How will I know I have sanded far enough down? Do you have any pictures? This will be my first time doing anything like this and I severely don't want to mess up

  4. #4
    Join Date
    Apr 2007
    Location
    Ridgecrest CA
    Posts
    66

    Default first time is a learning process.

    Quote Originally Posted by [1990]525
    Actually I planned on masking the windows when I got there I was not sure if newspaper would be proper to use because I imagined it being too thin to really protect. How will I know I have sanded far enough down? Do you have any pictures? This will be my first time doing anything like this and I severely don't want to mess up
    sanding,preping,and masking are painstaking,time consuming tasks.it sounds like you are seeking a factory quality paint job.if you want perfection you are gonna have to pay pay pay pay pay.is the shop cool with you masking the car?.alot of the tape is applied directionally so it can be removed when the paint has set just enough to adhere but not lift.all trim that can be removed should be removed,all lights,grills,bumpers,mirrors,locks,outside window scrapers,running lights and side markers.the less you mask the better the result.sand flat surfaces with da sander and all contours by hand,if you go to bare metal in any area youve got to touch up with compatible primer,i wont get into etching.any area that dosent get sanded or at least cleaned to remove all traces of anything other than clean paint will be prone to peeling.be really carful with the high power spray washes.i just talked myself out of ever painting another car.you can totally tell when you are through the clear coat by wiping the area with a damp towel.oils of any kind are your enemies,you have to have really clean air for your sander,wear long sleeve shirts and dont lean on the sanded pourus paint when your sweating,thats really tough to remove completely.if you get through it you will have a really sano looking ride. bones

  5. #5
    Join Date
    Feb 2005
    Posts
    115

    Default

    Quote Originally Posted by bones
    sanding,preping,and masking are painstaking,time consuming tasks.it sounds like you are seeking a factory quality paint job.if you want perfection you are gonna have to pay pay pay pay pay.is the shop cool with you masking the car?.alot of the tape is applied directionally so it can be removed when the paint has set just enough to adhere but not lift.all trim that can be removed should be removed,all lights,grills,bumpers,mirrors,locks,outside window scrapers,running lights and side markers.the less you mask the better the result.sand flat surfaces with da sander and all contours by hand,if you go to bare metal in any area youve got to touch up with compatible primer,i wont get into etching.any area that dosent get sanded or at least cleaned to remove all traces of anything other than clean paint will be prone to peeling.be really carful with the high power spray washes.i just talked myself out of ever painting another car.you can totally tell when you are through the clear coat by wiping the area with a damp towel.oils of any kind are your enemies,you have to have really clean air for your sander,wear long sleeve shirts and dont lean on the sanded pourus paint when your sweating,thats really tough to remove completely.if you get through it you will have a really sano looking ride. bones
    Thank you for letting me know that I have no chance of pulling this off.

  6. #6
    Join Date
    Nov 2004
    Location
    Gateshead,UK
    Posts
    926

    Default

    Have you had the opportunity of watching someone paint a car? You can learn a hell of a lot just by watching someone prepping then painting a few cars. As Bones said, you will get a much better result if you can remove every bit of trim from the car, rather than just masking things up. It does take a long time to prep a car but the more effort you put into it the better the finish will be. Ideally you want to be painting inside the A,B & C pillars too. This means simply removing all the door seal rubbers and sheeting up the 'hole' so you can spray the car with the doors open. Then you won't see any colour mismatch or peeling paint around the doorways. Don't be put off by all the work involved - if you have the time, patience, a good place to work in and are able to get a hold of the equipment you could pull this off.

    HTH,

    Shaun M

  7. #7
    Join Date
    Dec 2006
    Location
    Adelaide Hills
    Posts
    75

    Default

    First question - why are you going for a full squirt? Are you changing the colour or staying with the original colour? I would strongly counsel against doing a major colour change, because then you absolutely have to take off door trims, paint inside doors and door shuts, under bonnet and boot etc. Not worth it unless you have plenty bucks to spend and want to have a show quality car

    As previously advised, take off all trim, side moulds, lights, etc - otherwise you have to mask these off and you get paint edges which are a total give-away that you've repainted. Basically unless there is damage which needs repairing before painting (dents, deep scratches etc) then all you need to do is give the original paint a really good scuff with a Scotch-brite pad dipped in flatting paste like Scuff-it. Don't use "sand-paper". If you have to use abrasive papers use wet&dry carborundum papers no coarser than 400 grit. This provides the new paint with a good key to ensure no delamination down the track. An orbital air sander takes a lot of the hard work out of the job.

    Don't sand back to bare metal unless the original paint is delaminating or really poor quality with cracking or oxidations going back to the primer coat.

    You have to be using an angle grinder to get past bare metal and really **** up.

    After flatting back every panel, use a product like Prep-Sol (wax & grease remover) with plenty of clean cotton rags to remove all surface contaminants. Assuming you're not painting the car yourself, your panel shop should use a mid-coat adehesion promoter like DuPont's 222S - it's like double-sided tape for paint, which chemically bonds to the old paint and provides a good key for the new paint. Unless you have areas which have been repaired using body filler, or have rubbed back to bare metal, generally there is no need to use a primer.

    However, if you are determined to apply a primer coat yourself, go for several light dry coats rather than a heavy wet coat. Allow to flash (paint goes dull and flat) between coats, then apply a light guide coat of a contrasting colour like black, and using 1500 grit wet&dry de-nib the primer - wet rubbing using plenty of water. Highs and lows in the paint surface will be exposed by the guide coat. If you intend to use a high-fill 2-pak primer to enable you to get the absolute best finish, ultrasmooth and mirror-flat, make sure you use a proper respirator.

    Hint: practice on something that doesn't matter first ......
    June 88 535iA, 173,000 km; Sep 00 735i 170,000 km

  8. #8
    Join Date
    Jan 2007
    Location
    San Jose, CA
    Posts
    267

    Default

    Did this job ever get done? I noticed everyone has done a fine job of making a mountain out of a mole-hill and completely discouraged the OP. This is my trade and an E34 is one of the simpler cars to mask off.

Similar Threads

  1. Priming oil pump
    By Jon K in forum 5 Series BMW
    Replies: 8
    Last Post: 03-24-2008, 08:21 AM
  2. Fuel pump not Priming...any ideas??
    By dls322 in forum 5 Series BMW
    Replies: 4
    Last Post: 02-21-2008, 01:50 PM
  3. MAF or masking another culprit?
    By zuzuk212 in forum 5 Series BMW
    Replies: 1
    Last Post: 02-21-2008, 07:51 AM
  4. Replies: 18
    Last Post: 10-12-2006, 09:40 PM
  5. Air Conditioner Issue...advice is appreciated
    By nyc525iTe34 in forum 5 Series BMW
    Replies: 4
    Last Post: 07-24-2005, 07:02 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •