Preparing Surface For Airbrush – Part 3

How many times did you get to paint plastics along with other surface like metal? These days car – it’s not just a piece of metal on wheels but a bunch of plastic details as well.

I know there’s many people who don’t care much about plastics and just mask it with tape, but there are “masters” (as they call themselves :)) who just paint it the same way as the body of the car and don’t even care to prepare it in any way. So bumpers, side mirrors, spoilers and many of tuning additions that are mostly made of plastics can sometimes, even by small accident, crack and need to be painted after repair again or even replaced. If surface is not prepared properly the paint starts to flake. Even if you painted your car just a month ago and it looks great, how is the car going to look like with peeled bumper? Not just a car surface is the surface to go.

There are many other plastics that require the same approach. Airbrushed cell phone or airbrushed laptops is not unusual these days. Airbrush artists look for any surface to express themselves. Painting on plastics is very popular within modelers community too.

I decided to separate this article into three chapters. In the first I’ll tell you what it is a plastic, then you’ll see eight ways to make your plastic adhesive and at the end a few words about plastic primer.

What is it, that thing called plastic?

Plastic is a substance made of many different synthetic materials with “great” properties by really clever people in chemical laboratories :). Depending on its structure, every plastic, in similar situation can act very differently.

It means that plastic used outside the car, for example, will require different preparation as plastic inside the car, plastic cover for phone or laptop…

Generally you can run into two kinds of plastics. One will require special preparation with primer coat and one that doesn’t need any. There are two very simple (I would say primitive) ways to find out which one do you have.

1. Test for Burning

If you can get a small piece of the plastic that you don’t really need, try to fire that up. If it burns making black heavy smoke with almost no fire, it means you don’t need any special preparation. If you see nice clear fire similar to candle then you need to apply primer for plastic before you do base coat.

2. Test on Floating

This one is easier as you don’t have to destroy or burn anything, just put your plastic into some reservoir with water and check if it floats or sinks. If it sank then you don’t need any primers. If it floats then you will need a primer coat.

What is the process of painting plastic?

For example, if you bought a new bumper and want to make it look similar to your car coat then try the following procedure:

  • good wash
  • degrease
  • coarsen (using abrasives)
  • apply plastic primer
  • apply base (acrylic) coat
  • apply pigment (your art…)
  • apply clear coat
  • enjoy your work :)

If you want a real quality I will recommend to add special elastic additive (or flex agent) to your acrylic coat. It’s a special liquid in a bottle which makes your coat elastic so even if you expose your surface to physical straining nothing will happen to your painting.

If you found out that your plastic does not need primer then follow these instructions. Wash it and degrease as best as possible, use anti-silicon if you can. Then coarse the surface making it adhesive. Degrease again and spray base coat. After coat dries out, make it adhesive again (in case of car use P320 for classic enamel or P400-500 for Candy with clear coat). Don’t forget to add flex agent to your paint.

Manufacturer of this additive will not tell you this but when you use flex agent you will get into small difficulties. Sandpaper will get stuffed with dust more often so you will have to use more abrasives.

If your plastic burns like a candle or floats on the water (plastic needs primer) then the most important rule here is to degrease the surface really, really good, even from manufacturing lubricants. Next you do the same as above, the only difference is before you spray base coat you have to apply special primer for plastic. Usually it’s clear and dries fast. It is essential to use one or two coats. You don’t have to necessarily use abrasives before applying base coat.

The priority here is to keep painting premises free of dust.

8 ways to make plastic surface adhesive

First of all degrease the surface (water and solvent based mold release agents, wax, grease, fingerprints and any other contamination). Usually it can be done by washing the surface with soap and water. I can also recommend Air-Master degreaser.

Then we have to get rid of any dust. This can be done with just a napkin.
Now you have to choose which way is best for you. Don’t do all of them, just count on your possibilities.

1. Scotch-Brite pad with grit 360, the dry way – one piece of this pad can easily be used for at least 20 laptop covers.

2. Matt-paste (3M Scuff-it 50018) and Scotch-Brite, the wet way. Plus of this procedure is that you save some scotch-brite, more efficient and even more adhesive surface. Minus is that during scuffing the paste creates a lot of saprophytic dirt which you have to wipe all the time to see the result. When finished I recommend to use rubber squeegee to get rid of the all the paste and then just wipe it clean with paper rag.

3. Synthetic Abrasive sandpaper on 3mm foam rubber (sponge). Actually it’s a budget version of 3M SuperFine sponges. Can be used in dry and wet way.

4. Legendary SuperFine sponge from 3M. Probably one of the best materials to work with to prepare your surface but at the same time expensive and won’t last long. I would recommend to use this only for small projects like mobile devices. Can be used in dry and wet way, but thanks to its quality there no need to go wet way.

5. ABRALON Polishing Disc P1000 dry way

6. ABRALON Polishing Disc wet way (using water, not matt-paste)

7. Abranet – Mesh structured and probably the softest materials of the all abrasives. The abrasive medium is Aluminium Oxide. The open nature of this product allows dust from sanding to fall through the mesh avoiding clogging the abrasive with it.

8. Abrasive sandpaper wet way – Last and probably the most common, cheapest but not the best way to prepare plastic surface.

Plastic Primer (adhesion promoter)

We can use Bulldogs Bond-Flex-Tie Coat spray, Quickline 0.4 Plastic Primer spray or Air-Master primer in the bottle, this really does not matter that much as they all serve their purpose. Usually you should apply 2 coats of primer. Only thing to remember is that after you apply primer coat you should apply paint before primer will lose its properties (should be up to 10 minutes at 20°C or 68°F, so don’t think of applying primer on one day and leave paint coat for another).

Whichever way you have chosen you should get good results at the end. The only thing that left after we do a clear coat is polishing. But that is another chapter we’re going to look at some time soon.

If you have any recommendations or you disagree with me at some point then don’t hesitate and leave us a comment bellow.

Leave a Comment