Paint Application 101 – "Big areas"( in a booth)

I am going to break this down in two sections, the first on conventional colors and the second on custom colors.

If you have read the previous articles, you can now get to it! You should make up a checklist of what you will need, especially if you are going to someone else’s shop.

Here’s the list:
1) Wax and grease remover – use to wipe down just before painting

2) Wipers to use with above – low lint or lint free disposables are preferred

3) Air blower – narrow tube preferred to get in to crevices

4) Tack rags – (2) new ones to use as a final wipe

5) Paint strainers (10) – use medium if you are using a metallic colour

6) Mixing jug – empty can to mix your paint in with straight sides

7) Mixing sticks – graduated stick to accurately add paint/hardener/reducer in correct amounts

8) Masking tape – automotive grade, if there is a lot to mask take a few rolls of ¾” and a roll of 2”

9) Masking paper – a coated paper is best (never news print!)

10) Lacquer thinners – to clean your gun

11) Tech sheets – to check your mixing ratios and flash off times between coats

12) Fittings – correct airline couplings for your blower and gun

13) Clean spray gun – if you use a gravity bring a stand holder so you can fill it easy

14) Disposable gun air filter – cheap insurance for extra clean air

15) New disposable paint suit – get one that fits you tight but still allows full movement

16) Paint mask – clean dual cartridge mask with new pre-filters that fits your face well

17) Disposable latex gloves – make sure they fit your hands tight

18) Paint, hardener, reducer (have a couple of speeds available)

19) Fine sand paper and a gray scotchbrite – to catch any missed areas for adhesion

Let's Get Started
Before final masking and just before putting it in the booth, thoroughly blow it off with lots of air pressure over and over and over everywhere (this is the biggest single secret for clean dust free finishes). If you have masked areas already that have primer on them, remove and re mask (nothing worse than having a chunk of primer blow of onto fresh paint).

In the booth, wash the car with wax and grease remover (a wet rag on and a dry rag off) and change rags often. Don’t be surprised if you see some areas that need a little sanding – the lighting in a booth shows everything – fix it.

Wash your hands, suit up and perform a final blow with the booth running. Then, open up your tack rag and slowly wipe down all surfaces flipping it over as you go. I like to blow off my suit and apply a static guard lightly to my suit just prior to painting.

Mixing Paint
Mix your paint or sealer (if you are using one), as per the tech sheets. Mixing sticks have graduated numbers. Some are marked specifically for what you are mixing and some are “universal”. If your mix ratio is for example; 2 : 1 : 1, on a specific stick you would add paint/sealer to say number 4 on the left side then hardener to “4” on middle scale and reducer to “4” on third scale. On a universal stick, you add up on the same scale, paint to 4, then hardener to 6 and reducer to 8 to keep the same 2:1:1 ratio. Pour your mixed paint through a strainer in to your gun until almost full. Mix enough paint for one complete coat (on a big car this is about 1 ½ to 2 quarts of mixed paint); this will let you adjust your solvent on subsequent coats.

Have a Plan
It is important to have a pattern figured out before you start applying, know where you will start and where you will end so that you will get an even application with wet shiny paint everywhere - this is vital when doing large areas.

Tip: on cross flow booths move in a pattern from the filter end of the booth ending at the exhaust end, similarly in a downdraft top to bottom (this will follow the airflow).

I have seen (and used) many different patterns to spray a complete car. There is no one particular one that is best. It is important that you stick to the same pattern each coat to get an even application. I usually start at the roof middle (passenger side), ending with the quarter panel and do the same on the driver’s side, finish the trunk and rear then move up the passenger side from the quarter panel and do the same on the drivers side finishing with the hood and the front end.

Laying it Down
The first coat I always apply a little light, spraying wet right off the bat makes the finish prone to getting a few fisheyes (small holes where the paint does not stick do to some contamination left). On high solid two coat paints, I usually apply a light coat and two medium to wet coats, unless I use a sealer, then just two full coats (but the sealer is applied light for first coat). Most painters turn their gun’s fluid tip in a few turns for the first coat – restricting a full trigger and back it out for subsequent coats.

When applying paint use a 50% overlap while spraying, using a full even fan (about 6 inches away). Do not arc your passes (a natural movement of your arm and wrist), train your wrist to keep the gun at 90 degrees to the surface the full length of your pass (this takes practice – try spraying a few long flat panels to get the hang of it first). Try to make passes that are long but comfortable to minimize the number of over laps.

Tip: do not end your passes on a door edge or handle – extend past it - as when you move on you will end up double coating a little and these edges will end up heavy or sagging.

Paint will run easier on sides than top surfaces (blame gravity) so spray slower and heavier on roofs, hoods and trunk lids that are horizontal and visa versa on sides. Don’t be afraid to get down on your knees to finish bottoms – the goal is to get paint everywhere. On raised contours such as fender lips – spray across them – do not try to follow the contour or you will get sags. When you have deep indents to cover (such as headlight openings), turn down the pressure and spray quickly until covered and just wet. Sharp contours on sides or projections such as mirrors, aerials, scoops etc. require extra care to prevent sags. Again, gravity is the enemy so apply accordingly.

The sign of a good paint job is an even finish everywhere, no dry areas and little orange peel (texture). If you are not very experienced, do not try “maxing out” the finish (painting just to the point of runs – smooth like glass), a consistent finish that is a bit orange peely can be made almost perfect with some colour sanding and polishing much easier than one full of runs. There is a feeling of great satisfaction when you “lay down” a nice finish – very addictive – just warning you.

John