Airbrush technique

2

2002 Maxima SE

New member
I have chip on my bumper all the way down to the plastic. Luckily, the car is black and so is the plastic.



I plan to airbrush it this weekend, but I have some questions:



1)Do I need to primer the chip or can I just sand it (since the bumper is plastic and not metal)?



2)How many passes can I make with an airbrush before I need to stop and let the area dry?



My plan is:



Mix one part touch up paint and two parts lacquer.



1)Mask with tape. Fill chip with paint from airbrush and allow to dry. (not sure how many passes to make before allowing to dry and repeating)

2)Repeat until it is level.

3)Un-tape and wetsand the area covering a few mm beyond the scratch.

4)Polish.



Any help or other websites you can provide would be helpful. I have tackled chips with the brush/toothpick technique before but this is my first time tackling with an airbrush.
 
Thanks!



I guess having not used an airbrush before, I am a little worried about putting too much (where it runs) or two little (where it is freckled). I'm going to practice on a piece of cardboard to get my technique.



Is the 2:1 ratio of thinner to paint to much? I have read about mixtures 2:1 and 1:1 but it seems to be personal thing. I figured the thinner I could get it to go on, the better chance I have of getting a good fill and match for my paint.
 
Wow an airbrush...I never even thought of that!



I have touch up paint....I have a compressor....



HMMMMMM!



I would guess that you would want to paint it as slowly as possible...i.e. do the lightest coats possible and wait between coats.



If anyone knows about thinning ratios and the ratio for the clearcoat that would be awesome...this might be worth a try...
 
I have a Paasche VL which can put out a spot no bigger than

2mm by 2mm if you're careful. This works well for chips, but for

the tiny pinhead-sized rock 'pecks' or rash the wick-off-the-toothpick method is better.

Even having used one before I still practice on something

inconspicuous first.
 
Not that Iam an expert either, but from what I have learned in painting, this would be my approach.



Since this is a larger area the edges of the chip need to be feathered out by sanding. Now you have an area that if viewed in a cross sectional manner is lower than the rest of the bumper, this must be filled in and made level with the surrounding area. A primer filler of surfacer that is made for plastic or rubber type bumpers should be used or it will not stick or crack over time (this I learned the hard way). Be sure and sand a little beyond the chipped area so the primer and paint will stick. It will take multiple coats of the primer to fill this in. Once the primer has dried according to the instructions on the label, use a small block and sand the primer down until the edges have a feathered look, this process may take a few spray sessions.



Once you are satisfied that the chip is filled in (it should appear to be just a small gray spot on a chip free bumper) shoot on the color coats and sand with 2000 grit and polish out. If you get a pretty smooth final color coat you may be able to just polish it out.



Before you do this it might be good to try your airbrush techinques on something other than the bumper.



Gary
 
Gary,



So, roughing up the plastic with 1500 or 2000 grit won't be enough?



If I fill the area in with primer, won't the paint layer stick up above the rest of the painted area?



Being a newbie, please explain feathering the edges. I am assuming this means to make them more of an angle so that if this was a cross section, I would go from:



|______|



to this:



\______/
 
Maxima



You are right about 1500 or 2000 being a little too fine a paper for the initial sanding, I would use 800 or if you can not find that use 600.



Again you are right that when you fill in this area with primer it will be higher than the surrounding area. This is why you take or make a small block out of wood or some other material that is slightly larger than the chipped area and place the sandpaper around this block and sand down the primer until it is flush with the undamaged part of your bumper.



Your little diagram is correct about feathering out the chip before applying the primer.



Any more questions feel free to ask, not that I may have them, but someone will.



Gary
 
Thanks. This helps.



Gary,



One more question about the filler.



Again you are right that when you fill in this area with primer it will be higher than the surrounding area. This is why you take or make a small block out of wood or some other material that is slightly larger than the chipped area and place the sandpaper around this block and sand down the primer until it is flush with the undamaged part of your bumper.
Click to expand...



What I'm saying is that you have a chip that looks like this against the rest of the car at a cross angle (where * represents the hole):



***==========

***==========

=============



I fill it in with primer and it looks like this:



===

===========

===========

===========



I sand it, and it looks like this:





===========

===========

===========



My question was (but poorly stated) if I now add paint, I will be back to this:



===

============

============

============



And once I sand it level, it will expose the primer. Would it be better to add a level of primer that will not quite fill in the hole, sand inside the hole, then fill with paint?
 
Maxima



Your diagram is correct about the level of the primer compared to the surrounding area.



If you use a laquer based paint it is possible that the filled in spot will show up again under the color coat. Laquer is a hot type paint that does penetrate the surface it has been sprayed over. A solution to this is to spray a sealer over the primer first. What I would do is use a urethane based enamel for the color coats and you will not have this problem. The primer filler that you use will have to be purchased at an automotive paint store and they can give you some ideas on this application.



It is true that once the color coats go on and you either sand or polish out the final coat you can go through the color coats to the primer. I would put on at least five coats and polish only if you get nice smooth color coats. If you do sand or polish down to the the primer you can just sand this and shoot more color coats on (trial and error is one of the ways we learn).



Hope this helps, Gary
 
Thanks Gary.



I'm still confused on the paint though. If the paint is higher than the surrounding paint, then there is no way I can get it even except to take it down to the primer (which is level).



Shouldn't the primer be one or two layer's lower than the surrounding paint?
 
Maxima



Technically you are correct that the final paint layer will be slightly higher over the repaired area, but remember you are applying paint beyond the primed area to blend in with the main coat of paint on your car. The slope or gradient from the spot to your factory paint is so gradual after a little sanding/polishing that your eye will not pick this up.



Once again I encourage you to try this on some other material (plastic, metal, but not wood this absorbs too much) to develop a technique that will work best for you.





Gary
 
Thanks for the discussion...very helpful. I might ahve to order and airbrush and try this. At the moment my bumper has a little "problem" and needs to be replaced. There is also a nice chip (my rear bumper is not representative of the rest of my car! :) ) for me to try this out on. I can't wait!
 
endus,



If you do, how about take pictures and post them. I won't be receiving my airbrush until June 18, but I will take/post pictures when I do the work. Thanks!:bounce
 
I don't have an airbrush yet either. I haven't even ordered it yet.



The other problem is that I have a ton of new detailing products to try, and can't even try them because the weather here in Boston is so poor. I am just hoping that I *might* get to wash/polish/wax my car this weekend...since it will be the first weekend in a month or so that it didn't pour down rain the whole time! Besides that I still have to dynamat my trunk and change my oil...so I think you'll beat me to trying out the airbrush. :)
 
Busy man. :) I'll take pictures for ya.



Some questionson clearcoat:



I haven't heard anyone mention clear coat. Would I need to add a layer of clear coat and if so does this occur after the sand/polish phase?



If I do add clear coat, do I dilute it with acrylic lacquer thinner like the paint?
 
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