How to Paint With a Spraygun




About: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output devices. His detailed drawings of traditional Pacific...
Here's how to use a spraygun to paint your projects and make them look great. A spraygun is a lot faster than a paintbrush. The result looks a lot better too. No brush marks!
Make everything around you look shipshape and professional. A wise lady once told me "A project isn't finished til there's a "finish" on it. Get it?"

Any object tends to look like crap after it's been outside for a while. Metal rusts. Paint flakes off. Wood discolors and starts to crack. And the project you spent so much time on is yet another eyesore to irk the normal people.

A spraygun is the magic wand that will solve your problem. It really is just like magic.
Paint a multicolored object all one color, and it suddenly looks like a real thing, not some crap stuck together. Paint it white, black, or grey to match the theme of your surroundings, and suddenly it vanishes. It's become a part of the surroundings. No one would think of making you get rid of it.

I just made this metal hand truck look like part of the solution.
A few minutes ago it definitely looked like part of the problem.

Stuff you'll need:

Safety Glasses
Hearing Protection
Rubber Gloves
Filter Mask with organic vapor (charcoal) cartridge
Air Hose
Pressure Regulator
Angle Grinder with Cup Brush
Wire Brush
Sticks, rags, and something ugly, rusty, and dry to paint.

Here's the motion you'll be making with your spraygun:

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Step 1: Safety Gear

The glasses keep paint droplets, flying dirt and wire bristles from hitting your eyes.
The mask keeps your lungs and brain from filling up with solvents and dirt.
The rubber gloves and long sleeves keep solvents from soaking in through your skin.
They also keep your hands skin-colored.
The jackhammer headphones preserve your hearing for future enjoyment. They also play mp3 lectures from the London School of Economics about how Instructables is awesome.

Step 2: Spraygun, Airhose, and Regulator

This is a "touchup" gun I got for $10 or so on sale from harborfreight. I also got some brass quick-detach fittings, some teflon tape to seal the threads, an airhose, a coiled hose, and a pressure regulator with a gauge.

The regulator has a water trap, which would help if the air here was wet. Some air compressors put a lot of water and/or oil into the air hoses. When that shoots into your paint it makes a mess. At an autobody shop they put an airfilter/watertrap right on the gun. The regulator goes near your gun. There's another dumb one back near the compressor, but by the time the air has flowed the half mile out here to the front line, that regulator is just another drag. You need this last-chance regulator out here near the gun to actually know and set the gun's pressure.

If you don't have a compressor you can use the airconditioner compressor on your car or the pump from an old refrigerator. Even if the chill is gone from the unit, it's still good enough to pump a lot of air. If your pump is wimpy it's not the end of the world. Get a smaller gun, bigger air tank, or wait for the pressure between shots.

William Martinez says that in his native El Salvador they skip all this nonsense. They spray cars with a hand pumped bug sprayer from a hardware store. You know, the thing from Tom and Jerry cartoons that looks a little like a bicycle pump with a can at the end.

I've also used hand-held airless sprayers. They're pretty good for dribbling paint on the pavement, taking apart, and giving to other people.

Step 3: Wire Brush the Metal

A hand brush is plenty for most jobs.
Don't go nuts, just make sure you've brushed everything that looks rusted or flaky.
The secret is that the most important stuff to knock off is the stuff that's easiest to remove.
I learned about wire-brushing rusty metal from my Dad. That's how they did it on the farm.

Step 4: Power Brush

For heavy rust or badly flaking paint, an angle grinder with a wire brush wheel makes the work go fast. I prefer the "Twisted Bristle Cup Brush" style seen here.

If you're spraying a car you'll probably use a sanding disk or an orbital sander with 200+ grit paper to scuff up the whole car. Wet-sanding by hand with 400 grit is just as good. Use the cup brush on the rough and rusty parts.

Step 5: Free Paint!

Paint is free unless you're in a poor country where waste is rare.
In a rich country everyone else already bought too much paint. Now they're worrying about toxic disposal fees and trying to give it away. Most towns have a paint reuse program.

At the SF transfer station ("the dump") they mix all the partially full paint cans together to make a single mud color. Then they try to give it away. I hope that works for them.

I scavenged these cans of oil-based paint and the can of acetone thinner.
If you care about mother earth you might hold out for "low-VOC" coatings.
Those are types of paint that emit less solvents to the atmosphere.
My understanding of scavenger economics says it's okay to use the old stuff if you're not buying it new. I seem to recall acetone is the least harmful of the polar solvents. Please correct my facts and/or philosophy.

There are two basic types of paint. Oil-based, which you thin with solvents, and Latex, which you could thin with water. But you aren't usually supposed to thin it. You can clean it out of your brushes with water. Latex is good on wood. It makes a semi-permeable water repellent film that lets the wood breathe a bit. Sort of like a gore-tex jacket for wood. Some expensive latex paint can even be put below the waterline on boats.

Oil-based paint is easier to spray because you can thin it out more without hurting the film quality. It's good on metal because the oily molecules repel water like a squashed duck.
Rust-O-Leum is oilbased. "Alkyd" means oil-based. "Enamel" used to always be oil-based. Now some latex paint has that word on the can. Humans are a bunch of sneaky bastards.

Step 6: The Real Opener

Don't use a screwdriver to open paint cans. It bites the lip of the lid and makes the seal leaky.
Then you'll get braindamage from breathing fumes and your paint will dry out in the can.
Get a real opener like these. Paint stores give them away for free.
The best ones look like this curved one. Your life just got better.

Step 7: Why Grey?

Grey #1!! Grey roolz!!!
Grey is the best of the primary colors, the others being black and white.
Why is that? Here's the comparison:

White has a lot of advantages. It adds light to your surroundings. It makes things look clean like a whitewashed Greek village, the kind none of us will ever visit.
Titanium dioxide is the most common white pigment. It's very opaque and conceals other old colors under it without a lot of coats. Any color that contains some white also covers very well.
Unfortunately white gets dirty really fast which doesn't look good. Solara's white decks look pretty dingy now. And the glare off the white(ish) decks is excessive on sunny days. A white thing that's scratched and rusted looks very scratched and rusted.
Bodymen ("panel beaters" in the commonwealth) know that white is the color that makes dented bodywork look the worst. The eye is very sensitive to the subtle shadings of an uneven white surface. But white cars are popular in hot sunny places because the sun doesn't heat the car so much.

Black hides rust pretty well when it starts rusting through. So you won't have to repaint so soon.
Black things get hot in the sun and dry out quickly if you're in a damp northern type place.
Carbon is the usual black pigment. Soot in various forms like "lampblack" are popular sources of the fine carbon particles needed to make a good pigment. Feel micro-good about sequestering tiny amounts of carbon!
Black surfaces can get dirty pretty easily since most dirt is a lighter color.
The glossyiness of black paint is a big deal. I don't know why. It's hard to match from one can to another. Expert readers insist that shiny black, not white, is the color that makes lumpy body work look the worst.

Grey hides bumps and dents better than black or white. It doesn't get hot in the sun but the glare doesn't blind you either. It hides dirt really well. It hides rust almost as well as black. You can mix the kind of grey you want from orphan cans of white and black.
Most importantly, grey things are invisible to normal people.
It psychologically blinds authority figures to your insane behavior. After you've painted all your stuff grey, it will appear as a unified, highly organized system. You will appear to be an indispensible member of a team.

Step 8: Thinner and Viscosity

I'm thinning my paint with acetone to make it spray properly. If it's too thick it will look splattery or speckly. If it's too runny it'll be easy to get "runs" or drips in your finish. I like acetone because it dries fast. And I seem to recall that it's not extremely harmful. But maybe braindamage has addled my memory of the USP manual.

I thin the paint to about 4 centipoise viscosity to make it work in my spraygun.
There's a lot of variety in sprayguns. Read about yours and do what they tell you. Or just goof around with it til it does what you want. Harborfreight has some cheap ones that are good enough to spray paint with.

The manual for your spraygun will tell you about the desired viscosity of the paint. Also a bunch of stuff about air pressures, flow rates, and adjustments. Possibly your spraygun will come with a "viscosity cup" which is a cup with a hole in the bottom for measuring viscosity.

Fill the cup. Count how many seconds it takes for the cup to drain. That's the viscosity in centipoise. Water is one centipoise and drains out of the cup in one second. Honey warmed in your armpit or cooking oil are thicker and slower. It drains out in 20 seconds and is 20 centipoise.

Some thinners won't work with some paints or varnishes. Don't test a new thinner on your show car. If you buy thinner at an autobody supply store they call it "reducer".They'll ask you what temperature and humidity you expect to do your painting in. It matters because car paint needs to sheet out and be all shiny. If you're in the SF bay area, regular lacquer thinner will work fine. Autobody stores do sell something called "paint thinner", but it's only for cleaning up the gun and other messes.

Step 9: The Stroke

The spraying motion is an art in itself. Move the gun at a constant velocity back and forth. Push the button after the gun is up to speed. Unpush the button before the end of the stroke. Overlap the strokes like shingles, wet on wet. Just like in this magnificent movie:

If you get runs it means too much paint or too much solvent in the paint.
Use lighter coats. Wait and paint on another light coat.
Go ahead and tell people you put 30 coats of hand-rubbed lacquer on your MacGuffin.

Step 10: Painted!

What a smooth grey thing!
It appears vital to our operations here on the base.

Next you'll want to clean your spraygun.
Instead I'm keeping mine wet by spraying something with it every day and keeping it out of the sun.
That sort of optimism is what causes sprayguns to fill with hardened paint.
Sort of like putting a dirty paintbrush in a plastic bag so you can clean it "later".
Read the cleaning instructions for your gun to see what the proper method is for that model.
I dump out the paint out of mine back into the can, wipe everything with a rag, then put some solvent in the gun, spray solvent, then dump that in the paint can to start thinning it for the future. I repeat that until I think my gun is clean. Spray the solvent at a surface to see how much pigment comes with it.
Some serious painters keep their gun in a bucket of solvent so the traces of paint left in it never harden.



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    27 Discussions


    8 months ago

    I have joined Instructables just to comment on this... amazing article!


    11 months ago on Step 10

    Excellent writing! I love your style. Thanks for this : )


    2 years ago

    Absolutely awesome - some of the best writing on the WWW. Thank you :-)


    3 years ago

    Thanks for taking time to do this. Most of the instruction out there goes right over my head.


    8 years ago on Introduction

    One more thing. I guess you've noticed how acetone eats right through latex gloves by now huh? Neoprene stands up to solvents. You may want to step up there.


    8 years ago on Introduction

    I watched your video and when I spray I put vertical strips up and down where I am going to paint first, then I fill in with horizontal stripes. Also good spray guns are 2 stage, that means at half trigger the gun will still spray air but the paint will be shut off. So don't stop airing just stop painting at the ends of each stroke. It saves on spitting starting spraying again. It also blows your over spray away so it does not ruin your previously applied paint.

    But I guess when spraying an old rusty dumpster every fleck that lands on target is a spot to the good. Still in all if you are going to teach you might as well teach right.

    I also tell people it all isn't in the wrist, wrist always keeps the gun perpendicular to the work, move at the shoulder, or beyond. But you were moving so fast I couldn't really tell what you were doing. But I do tell folks that it is all in the follow through. When you stop paint but keep on airing you follow through a little on each stroke. Really if you were going like that on one of my cars I'd have to beat you with a clue stick.

    Also you could learn a thing or three about how to properly clean a paint gun. Let me guess that is one of those $9.99 Harbor Fright specials?

    Anyhow I have to admit your dumpster does look better for you having painted it! It'd have looked OK if you'd rolled it too and you might have saved some paint.


    10 years ago on Introduction

    As a painter I must admit that everything here is horribly wrong, although it's not wrong enough for me to whine about it. It'll work fine for large, rusted-up trash bins and other items, although other objects would probably promptly fall apart and burst into flames. Since someone else already mentioned your arcing issue: That touch-up gun should be held with the top of your hand wrapped around it, finger resting lightly on the trigger. It seems like it would be awkward and uncomfortable, and it probably will be at first, but that gun is only meant to be used to blend single small panels. Also, always wear an approved paint respirator. Please. :( I would really like to see you do an instructable for a whole car. I keep picturing you as Red Green and I think the result would be awesome.

    1 reply

    Reply 8 years ago on Introduction

    I saw the touch up gun and thought it was cute. I have to agree with the poster though everything does look better with a good coat of paint on it!


    8 years ago on Introduction

    This maybe a question to an obvious answer, but with the air hose, generator, paint gun, and paint, and mask.. Are the other things must haves and if so why? (example) wire brush stuff like that


    9 years ago on Introduction

    First and foremost before starting to paint your car.Always hav won'te some chain long enough to ground the vehicle to the ground so static dust cling to your painted vehicle while it's wet.


    9 years ago on Step 8

     You can also thin with mineral spirits; more volatile but can be scavenged more readily I believe.


    10 years ago on Introduction

    Here,the bug sprayers are like rectangle barrels with a pump and a hose comes from it.Some even have backpack-style straps.But I have an airgun.


    10 years ago on Step 2

    Your opinion on those hand-held airless sprayers is good to keep in mind... and funny.


    10 years ago on Introduction

    Varsol was recommended on the label of one paint I used. But, it did dry kind of slowly, giving bugs plenty of time to get stuck in the paint. I got my viscosity cup from a Sears store in the US; dunno if they still carry them. Spray guns can be found at vintage auto parts swap meets... I got a vintage DeVilbiss gun for $1. Be aware that there were (are) some cheaper types of spray guns that were made to be used with very basic compressors; I think they were called "bleeder" types because air flowed through them continuously (even when not spraying). So, be careful, or just buy a nice clean new "imported" spray gun. ( I got a touch-up style gun made in Taiwan for about $25, and it works just as well as the DeVilbiss.) If you want a smooth shiny finish, sand between coats. Paint doesn't magically hide dents and scratches, it follows contours very faithfully. There's stuff called glazing or spot putty (in the auto body repair section) that can be used to fill small imperfections. One tiny drawback of spraying is how much work it is to clean up the spray gun afterwards.


    10 years ago on Introduction

    LOL, I had almost complety forgot about my dad spray painting items with a "bug spayer". 40 years or so ago dad painted a shed he built with junk yard paint he mixed to gether. Turned out to an acceptable flat yellow in color, and has clung to metal all these years now. By that time he had upgraded from the bug sprayer, to an air compressor, and an old devilbiss gun he picked up at an auction somewhere.Yes spray painting is the way to go, if one plans to be painting a lot of items, and is willing to make the investment. Good thing one's dollar today goes further in buying serviceable equipment than it did years ago.


    There's a reason that the US Navy paints everything grey ! Thanks for explaining it, Tim. Remember, as they say in the Navy, if it doesn't move, paint it! Grey of course.


    10 years ago on Introduction

    Oh, I might have missed it, but another almost mandatory thing would be to strain your paint, particularly if you are working out of open cans. You can use old nylons or buy those little paper funnel cup strainers from hardware stores and paint stores. The tips on these guns are quite small and plug easily if they get any crud in them. Does make everything look new and shiny though! This is what I do for a living (plus abrasive blasting), though I mostly use catalyzed polyurethanes and epoxy based coatings. I used to do furniture too, and with practice and the right prep, varnish turns out beautiful! Oh, and Tim rocks!

    1 reply

    Reply 10 years ago on Introduction

    Good point. I looked for my strainer funnels but I must have put them somewhere safe. I've tried varnish before which is quicker than brushing, but didn't seem to get into the wood quite as well and sure ran easily. Also I screwed up some varnish with the wrong thinner which made it milky.