Spray Painting

Does anybody here now anything about spray painting?
I recently bought a compressor and spray guns, etc. Now I want to learn to do it properly. I’m busy spraying an old fridge as an exercise, (though its a good fridge and can be used too).
Now, of course I’ve manage to create a few drips. How do I fix it?

My brother has spraypainted quite a lot over the years. He just completed a 19 seat Jet. But as for myself, no I dont know a lot about it other than what I have picked up from him.

However, I would suggest that you would need to let the paint dry completely and harden, then sand back the runs and repaint. It is important to let the paint harden properly, or your sandpaper will clog easily and pick up too much paint. In short you will make more of a mess of it.

I think generally you should lightly sand with a fine sand paper between each coat anyway, as this helps each layer key onto the next.

There are two things that are very important painting where we are. They are temperature and humidity.

Make sure you have a nice warm environment to paint in, but be careful of safety with regards to the fire risk associated with heaters etc. Especially when using lacquer or solvent based paints.
Warming up a room prior to painting is a good idea. Then remove the heat source.

A high humididty environment causes “blooming” in the paint - basically unsightly splotches caused by excessive moisture in the paint. It is not much good painting here when it is raining even indoors due to this fact.
We live in a rain forest area - very damp.

Do not get to eager to get a new coat on before the preceding coat has properly hardened and sanded, or you will end up with a “soggy” kind of result.
You also need the correct primer for any given paint.

In the case of the fridge it would probably go something like this:

Sand back existing paint quite hard.
1 coat of metal etch primer
Let dry
1 coat of metal etch primer.
Sand lightly when dry
1 coat of metal etch primer.
Sand lightly when dry.
1 Top Coat
Sand lightly when dry
1 Perfect Top Coat

Sand lightly and re top coat if any problems or skip the last sanding if this appears to put marks in it.

Cool, thanks thats allready some good guidance.

If you’re gonna be spraying a lot, get a respirator (not one of those little blue masks, they won’t help you fer sh*t). I assume you don’t want to end up with bowel/kidney problems.

yeah you got some good advice.

i own a spray gun also, but not a compressor (use the compressed air system at University)

mixing paints is the key factor which hasn’t yet been talked about, you will want the best thinners available for the top coat. these are often AAA labeled (here they are), otherwise the step down from that is Two-way thinners.

i do a 50% mix of thinners and paint, but its never acurate, you need to get good at judging it based on how the paint drips off the stiring stick (or whatever you are testing it with). its all a judgement call.

mixing it to thin will make the paint run easily, it will also be very thin coats and will look like bad coverage. mixing it to thick will make the paint go into strings in the air, and will land on your surface already dry, and will give it a textured effect.

when painting, start with the hardest areas then work to the flat surfaces. i.e. paint the corners first, as they will overspray onto the flat areas a bit anyway, but not vice versa.

paint in lines each one 50% covering the previous, and each one going past the edge of the object (so you are not slowing down and changing direction, while painting your coat). all fairly obvious things, but things its easy to teach to avoid learning the hard way.

Paint colour matching, if you are mixing your own colour, its better to mix it up in a large enough quantity so you don’t need to eye match, although eye matching is not to hard to get right, but it is risky.

for the finishing you will want to also put a clear coat layer over the top of the paint job, the clear coat layer can have a pearl finish in it which will be similar to a Specularity Ramp shader in blender (i.e. blue pearl over red undercoat)

metalic finishes are cool if you want to do anything like that. and also have you considered masking off areas and doing something like a metalic, on flat colour areas…

its all fun and games, but i’d definitely test it on other things than your final.


p.s. yeah definitely get a resperator, about $100+ (NZD) for a good one and the carbon filters. otherwise your brain is gone down the toilet, its really not worth being a hard man around spray paint. a classmate is a pro painter (we just do it for uni) and he uses all the safety gear, hes seen to many mental people as a result of not caring.


Errr, what paint were you spraying - lacquer, enamel, two-pack…?

The application and after-care differs for each:

Acrylic lacquer (automotive lacquer) dries fast. With something the size of a fridge you should be able to apply one coat, wait 15 minutes or so, apply the second and so on - up to four coats. You usually only get runs in lacquer if you’re being impatient or inattentive. It has a low-sheen finish when dry but can be lightly sanded and buffed/polished after a few days to a week (depending on temperature) for a very high quality shine.

Enamel (Automotive or domestic) dries slowly and must be applied carefully or it will build up wet on wet and run when you’re not looking. 2-3 coats will probably do it. You shouldn’t need to polish it but if you get runs you’ll probably have to wait weeks or months before you can successfully sand them back to fix.

Acylic Enamel (Two-pack) uses an isocyanate hardner for faster drying. Application is same as enamel and you shouldn’t need to buff it for shine.

I haven’t spray-painted for 15 years so there are probably more choices available but they’ll be variations of the above.

As Caolth said, get a respirator - even for one job. If you’re spraying two-pack (or adding dryers to regular enamel) get a full-on, heavy-duty carbon respirator. The two-pack dryer contains cyanide which accumaltes in the body and never goes away. If you want to commit suicide use a regular gun not a spray gun :wink:

The “secret” to painting (don’t tell anyone this) is even application and overlapping strokes. Work the gun from side to side staying an equal distance from the surface. If the surface curves, so must your arm action. Start the spray off to one side and finish it off the other. If you start and stop on the surface, you’ll get a vertical build-up. Overlap the horizontal strokes 50% to prevent streaks. Don’t have the spray pattern too wide - or to skinny (I always liked a slightly skinny pattern with the gun held further back than most books recommend).

Don’t apply it too dry or it’ll look like sandpaper. Don’t apply it too wet or it will run or at best, give you “orange peel”.

If you want real fun, buy an airbrush (ahhh, the memories :))

One last tip - don’t run with scissors.

Other than that, get hold of some some books. There’s a lot to learn if you want to do some serious painting.

I have sprayed paint and polyurethane on walls and furniture. GET A RESPIRATOR!!
something like this is what I use.
I notice a big difference in the way the spray comes out of the gun if I am using cheap paint or good paint. I think the best way to learn what your gun will do is to try it out with a few paints on some “test” jobs(cardboard boxes maybe). Buy a few quarts of different paint. Thin some way out to see what happens. You will get the feel for your equipment and learn some thing about paint. Read all the paint labels, you don’t need to follow all the directions but at least you might learn which ones you do need to follow. Good luck and please BE SAFE a solvent and air mixture can be very explosive and BAD TO BREATHE!!

Don’t rely on the compressors built-in air regulator. Buy a good quality one that includes a moisture trap.