Air Brushes, Spray Guns and Air Supplies

The lightest way to paint is to spray it.  The paint layer can be much thinner yet still be even and opaque.

Do not be afraid of airbrushes and don't get stressed over how much to thin the paint or how much air pressure to use.  When someone gives you a recommendation for air pressure or thinning that's all it is — a recommendation.

I have used my airbrush at everything between 15 PSI and 60 PSI.  Just set it up so it works for you.

Also see

• Painting Tools
• Covering and Finishing Materials for Flying Model Aircraft
• Klass Kote Epoxy Paint Review
• Shop Supplies — Contains information about various solvents

Airbrushes and Spray Guns

Thinning the paint is not as difficult as many people imagine.  There is not a "magic" amount of thinner that needs to be added.  The paint should be about the consistency of skimmed milk up to about the consistency of 2% milk.

Properly thinned paints spray on smoothly, flow out quickly and look dry within minutes.  If the paint goes on wet but is very translucent and watery looking then it is too thin.  If it spits and splatters, goes on a like dry powder or fails to spray at all then the paint is too thick or the spray tip is clogged which could be due to the paint pigment being too coarse to pass through the tip.

The key to airbrushing is simply practice.  Reading about it only gets you started.  I suggest you buy some artist's watercolors that come in tubes and practice spraying poster board.  That will help you learn how to thin paint properly, adjust the airbrush and the air flow.

When you are comfortable with that, practice painting patterns on the board.  Finally practice using cheap enamels on something non-porous.

When I start spraying a color I usually shoot an empty soda can to make sure the paint is thinned properly and the airbrush is adjusted correctly.  Spend an afternoon with your new airbrush, a couple jars of paint and it will all make sense to you very quickly.

Airbrushes come in a variety of styles with an equal variety of capabilities.  If all you need to do is spray coverage coats such as base or trim colors, then a single-action, external mix airbrush with a medium and large tip will do everything you need it to.  If you plan to use your airbrush to weather your model, paint murals or spray very fine lines then you will probably want an internal mix airbrush with a fine tip.

If you are not doing fine artwork and you spend over $100 on an airbrush then you are spending too much.  You can get a decent airbrush for under $50 by itself and from $60 — $75 in a set containing a hose, a bottle or two and an extra needle/tip assembly.

I will break it down quickly and explain the benefits of the various types.  There are three basic features that define an airbrush: Action, Mix and Feed.

Action

Single action	The air/paint mixture is set before spraying.  Pulling the trigger back opens the air and the paint at the same time.  Most single action airbrushes are on or off.  Some have a variable trigger — the further back the trigger is pulled, the more paint and air are released.
Double action	The air and paint are controlled independently while spraying.  Pushing the trigger down opens the air.  Pulling the trigger back releases the paint.  If you are gifted and coordinated (I'm not one or both of those things) then this type of airbrush offers the most control while painting because you can change the air and paint flow independently of one another.

Mix

Internal mix	Air and paint are mixed inside the airbrush before it is sprayed.  This style airbrush atomizes the paint into smaller particles and produces a better spray pattern.  They also are capable of spraying finer lines.
External mix	Uses the siphon principle.  Air is blown over the paint tip (an open tube) and the paint is drawn out.  The paint and air are mixed on their way to the surface being painted.  They are easier to use and clean and are good for coverage coats. As far as I know, external mix airbrushes are always siphon feed.

In addition to these there is also a turbo type airbrush.  I have no idea how these airbrushes work because they cost as much as BMW.  I think it is just another type of internal mix airbrush though.

Feed

Gravity feed	The paint cup is above the airbrush.  Gravity feed airbrushes allow less air pressure to be used and are good for fine detail work that requires the airbrush to be close to the medium.  Many of these have built in color cups and do not have the option to use a different size cup or jar.
Siphon feed	The paint cup is below the airbrush.  More air is needed than for gravity feed.  These types of airbrushes usually allow you to fit different sized bottles to match the task.

If you have never used an airbrush then it is a good idea to purchase an entry level unit.  For model work, we usually apply solid coverage coats of paint.  This is exactly what a single action airbrush is made for.  Double-action airbrushes are used for artwork where you might paint a stroke that needs more and less paint during a single stroke.

I purchased my double-action airbrushes thinking they would be more useful but so far they have not been.  I just do not need that much control.  I suggest you leave the double-action brushes to the artists unless you plan to paint murals on your models.  A variable trigger single action model does everything I need it to do.

Not shown here is the quart gun which is the same as a pint gun with a larger cup.  These are too big for most purposes unless you are painting quarter-scale models in which case it is probably the best choice.

A relative new-comer is the High-Volume, Low Pressure (HVLP) spray system.  I have never used one so I can only repeat what I have been told about them.  The benefit is that they use much less paint because the gun is pressurized forcing the paint out rather than the paint being suctioned out.  Less air is used and as a result there is less over-spray and less wasted paint.

If you think an airbrush is small, the mess it makes is not.  The overspray goes everywhere.  You can handle this in a few ways:

• Airbrush outdoors

  Not something I like to do for several reasons.  Particles in the air tend to land in the paint and you have to wait for calm, sunny days.  If I am spraying with a gun, then I spray outdoors if the weather is cooperative.  Even though I don't like it I do most of my spraying outdoors because there simply isn't a way to keep overspray contained unless I want to spend a week turning my shop into something like the government operation in the movie ET.

• Buy or build a spray booth

  Probably the best option, but booths sold through the hobby industry are too small for R/C planes and they are very expensive.

• Drop Cloths

  Cover the entire area, including the walls from ceiling to floor.  I cover the immediate area where I am airbrushing with plastic to keep overspray contained.  If I am using a gun and the weather is poor, then I will cover everything I can with plastic drop cloths in the shop.

Airbrush Accessories

• Needle/Tip Assemblies

  Many airbrush sets come with an extra needle or two.  Needles are usually three sizes:  Fine, Medium and Large.  It can be difficult to tell which needle is which so manufacturers created a standard to make it easy to keep from mixing your needles and tips.  There are engraved rings at the rear end of the needle.  One ring = fine, two rings = medium and three rings = large.

  It is important to use the correct needle/tip combination because each needle and tip has a different taper.  Using the wrong needle with the wrong tip will guarantee spray problems and probably damage the assembly.

  Aztec uses an entirely different method with their airbrushes.  The needle/tip assembly is already assembled and color-coded.  There are needles for different types of paints (acrylic/all others) as well as different effects (normal spray/splatter effect).  The instructions that come with the airbrush indicate what each color needle tip assembly is for.

  Take very good care of your needles.  No matter how much of a hurry you are in to get your airbrush cleaned and ready for the next color or to put it away it's not worth damaging the tip in the process.

  Airbrush needles are very fine and delicate.  If you bend it or damage it in some way it's toast.  One of the best ways to destroy a needle is to clean it and set it down on the table and then watch it roll onto the floor onto the tip.  I make a special effort when handling the needle to ensure its safety until it's assembled back into the airbrush body.  You should do the same.

• Color Cups

  Airbrushes I've seen are of two types.  One type has a built in color cup and that's all you get.  Other cups can't be attached.  These airbrushes are usually designed for a specific type of work and aren't considered to be multi-purpose.  Examples of this type airbrush are my Hansa 181 and 351 above.

  Many airbrushes allow cups to be attached.  Cups can be gravity or siphon feed.  These cups can be plastic or solid metal - usually chromed brass.  Siphon caps allow various capacity paint jars and bottles to be attached.

• Holders and Hangers

  Airbrushes that have a heavy jar attached can normally stand on the jar.  It's still easy to bump the airbrush off the table though.  Airbrushes with color cups attached have nothing to stand on and will lay on their side spilling paint everywhere if you just set the airbrush on the bench.  Many airbrush sets come with a simple airbrush hanger which is nothing more than a bent strap with a slot to allow the hose to hang down and a couple of holes to mount the strap with small screws.

  There are also airbrush holders that can hold one or multiple airbrushes.  These usually clamp to the bench.  The holders can be moved to various angles to prevent paint spills.  Many airbrushes are designed to be used pointed down which means if you hold the airbrush level and the reservoir is full the paint will likely spill out.  The holder can be adjusted to hold the airbrush in the correct position - pointed down.

• Parts

  Airbrush manufacturers and models come and go.  If you use your airbrush you will need parts for it eventually.  I use solvent based paints frequently in my airbrush which means using solvents to clean my airbrush.  Neoprene O-rings don't like solvents.  They last a few years and then decompose or break.  I've learned that it's a good idea to buy a couple packages of O-ring sets for my airbrushes as well as a replacement needle/tip assembly for the assembly I use most.

• Pre-Thinned Paints

  Manufacturers periodically release a line of "airbrush colors."  Maybe I'm missing something but I frankly think it's stupid to buy pre-thinned paint.  They charge you more for it and you get less.  For example, if you buy one ounce of normal paint you get one ounce of paint.  Normally paints need to be thinned at least 100% (50/50 paint/reducer) to achieve good spray results with an airbrush.

  Reducer is usually cheaper than paint.  That means you get two ounces of paint for the cost of one ounce of paint plus one ounce of reducer.  One ounce of pre-thinned paint usually costs more than the two ounces you get when you thin it yourself.

  Additionally, no paint I've ever used stayed spray-ready over time.  What I mean is that paint that I thinned two years ago for spraying will have some of the reducer evaporated if I want to use it today.  That's even in a well-sealed jar.  I would assume that pre-thinned paint does the same thing so any way you look at it you're going to need to thin the paint unless you use it all when you buy it.

  Now that I've said all that I could be absolutely wrong.  I've never purchased the stuff and never plan to because thinning paint is really no big deal and I'm not going to pay somebody to do it for me.  You can if you want to.

• Air Hoses

  You will need a good quality air hose for your airbrush.  I personally prefer braided hoses, but I do have a couple plastic hoses that work fine.  If you have more than one airbrush and they are made by different manufacturers, you can bet the hose will not fit them all.  You can buy adapters to fit almost any hose to any airbrush.

• Moisture Traps

  A good moisture trap is essential to keep water out of your paint which will create little bubbles in the paint job.  I use a moisture trap on the compressor itself and a second inline trap in the air hose.

Air Supplies

Your airbrush needs a compressed air supply.  There are four types that I know of:

• Air compressor
• Canned air
• CO2 tank
• Inflated tire (for those of you having an old tractor tire handy)

I personally recommend that you buy an air compressor.  A compressor has a ton of other uses in your shop so you can not go wrong buying one.

Canned air gets expensive very quickly.  They do not last very long and you are sure to run out in the middle of a painting session when all the stores are closed.

CO₂ is a good choice if you live near other people because it is quiet.  If you use a spray gun then a CO₂ tank will not last long.  I have heard a filled tank can last a year or so if you use it only with an airbrush.  I've never used CO₂ but by all accounts there is one other advantage to it besides being quiet.  It's dry which means you don't need to worry about moisture traps.  It's probably drier than using multiple moisture traps between a compressor and the airbrush as I do.

The inflated tire would require too much jury-rigging to get it work right and you still need some way to fill the tire — an air compressor for example.

If you plan to use an airbrush, but not a spray gun, then you can buy a compressor made specifically for airbrushing.  These come in several varieties as well.  The most expensive of the lot are the silent compressors.  They are what they claim to be — extremely quiet.

There are two reasons I have not purchased an airbrush compressor.  First, they are expensive — about 4 times as much as a larger, general purpose compressor.  Second, they can operate an airbrush but that is about it.  A larger gun or air tools require a larger compressor.

A general purpose compressor can be used for various other tasks such as inflating tires and operating air tools.  One of my favorite uses of an air compressor is to blow the dust out of a model structure prior to vacuuming it.  It is also great for blowing the dust from around hard to reach areas like the stereo knobs in your car and your home system.  Buy a blower attachment and turn the pressure up as high as it will go and you are in business.

The down side is that these general purpose compressors are very loud.  If you live in an apartment you will tick off all your neighbors every time you turn it on.  I folded up an old blanket and put the compressor on top of it.  That absorbed a lot of the noise but it was still loud.  Do not try to box your compressor in.  They get very hot and are air cooled.  I suspect you would burn one up pretty quickly if you tried to do something like this.

If you have space and the inclination you can build a closet to house your compressor.  When I said don't box it in I meant in a box that's only slightly larger than the compressor.  If you build a closet then you'd probably need to ventilate it but it would cut down on the noise and probably not overheat.  A lot of people build the closet outside their home which frees up the space in your shop and reduces shop noise.  If you want to go this route then research it first so you can find out what works.  I've never done it so can't offer any guidance here.

I also recommend that you buy a compressor with a built-in tank.  The tank prevents the airbrush from cycling with the engine.  In other words, it puts out a consistent flow of air rather than short spurts.  It should have an auto-shutoff so when the tank is full the compressor will turn off by itself and not turn back on until the tank pressure falls below a certain PSI.

Before buying a compressor make sure it can put out the amount of air needed by whatever you plan to use it with.  Spray guns, airbrushes and air tools have specific requirements — so many Cubic Feet of air per Minute (CFM) at so many Pounds per Square Inch (PSI) that they need to operate properly.  The compressor will also list it is capabilities.  Just make sure it all jives before plunking your money down.  For example, Badger lists the following requirements for the 400 gun.

Spray Accessories

An air regulator is a necessity to set the air-pressure for your airbrush or spray gun.  Most regulators come with a built-in moisture trap that is pretty much useless in my experience.  They do trap some moisture but not nearly enough.  I often feel a cold water mist coming out of my airbrush.  That's why I buy an inline moisture trap that mounts near the airbrush or spray gun.  Together with the regulator/moisture trap almost all water is removed from the air and doesn't end up ruining your paint.

Most regulators come with an air gauge and usually have a place to mount a second gauge.

An air gauge is not essential because you do not need to know what pressure is being put out for your airbrush.  You adjust the air depending on how your airbrush is spraying.  If you use your compressor for inflating things then a gauge is a good idea.

I recommend you purchase a larger hose for use with larger spray guns and other air tools.  Put a female quick-connect fitting on one end of the hose and a male on each of the tools so you can switch tools easily with using wrenches.  It is also a good idea to put a female quick connect on the compressor after the moisture trap and male connectors on all the hoses so you can switch these easily.

Always use Teflon tape on threaded connectors in the air line to prevent leaks and unnecessary compressor cycling.

I have a Lazy Susan made by Rubber Maid that I put my plastic models on for airbrushing.  These are excellent for this purpose because the part can be rotated to spray all sides without having to pick the part up.

Extra hands are nice tools for holding parts as well.  These generally have a heavy base and two or three alligator clips.  You can make your own with alligator clips purchased from Radio Shack that are crimped or soldered to pieces of coat hanger material.  The coat hanger is inserted into holes drilled into a scrap piece of wood such as a 2 x 4.

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