If you just want the answer without knowing why, then buy an Iwata Custom Micron CM-C Plus, if you can afford it (and think that your talent or ambitions justify such a precision engineered tool) or an Iwata Hi-Line HP-CH for a high end all round airbrush, else, and especially if you want something adaptable, easily customisable and with cheaper spares (needles and nozzles eventually need replacing), buy a Harder & Steenbeck Evolution Silverline fPc Two in One or a Harder & Steenbeck Infinity Two in One, depending on your taste. The nice thing about the Harder & Steenbeck airbrushes is that all of the add ons are interchangeable, so you can customise your airbrush a little to suit your needs and the way you want to work.
If you want to know a bit more about airbrushes and why these ones are appropriate for miniature painting, keep reading.
An airbrush is usually defined by three characteristics:
Where the paint is atomised by the airflow
What the trigger does
How the paint is contained and, therefore, how it is fed into the airflow
The only other common variable is nozzle diameter. Anything else will be down to differences between different makes and models or extra features and optional extras. You will also need a compressor and a few other supplies.
Internal or External Mixing
External mixing refers to the paint meeting the airflow well outside of the airbrush and these are usually (I’d like to says always but there’s the chance that there’s one out there that I have no knowledge of) syphon fed. The paint flow enters the airflow at roughly right angles. They are cheap to manufacture but don’t atomise the paint as finely as internal mixing airbrushes. Internal mixing refers to the paint and air mixing on the tip of the nozzle, or just beyond it. The paint flow and airflow are travelling in the same direction at this point and the paint flow usually leaves the nozzle with the airflow surrounding it. This gives much better atomisation and is ideally what we want for painting miniatures (or anything, really).
Single or Dual Action
Single action triggers will open the airflow and paint flow at the same time. Adjustment of the paint volume (if possible) is made prior to spraying, which allows no flexibility during work. This is bearable for priming but not for anything else. Dual or double action triggers are pressed to release air and pulled back to release paint. The extent of each action controls the amount of air and paint in the mix. On some airbrushes, the maximum paint volume and airflow can be limited to make fine work easier. These are features worth looking for, especially for the paint flow, as air pressure can be adjusted on the compressor’s regulator.
Gravity, Side or Syphon Feed
A gravity feed is a colour/paint cup positioned on the top of the airbrush and the paint enters the airflow as the needle is drawn back out of the nozzle. A syphon (or suction) fed airbrush relies on the airflow sucking the paint through a tube from a jar positioned underneath. This requires either greater dilution or greater air pressure than a gravity feed, which prohibits fine detailed work. A side feed is a hybrid, which allows for either but isn’t as good as either and gives the airbrush an odd balance because the weight of the paint and its container is out to the side. Being left-handed could cause a problem with a side feed too, as they’re usually made with the cup or jar on the right, which would be in a left-hander’s line of sight. The one advantage to a side feed is that when using the colour cup, it can usually be rotated allowing the airbrush to be used more easily in different positions, however, it still requires a little more pressure than a gravity feed and most gravity cups come with lids to prevent spills. Gravity fed is the best for miniatures as it allows for working at lower air pressures. The main advantage to the other types, especially the syphon feed, is that colour changes can be made more quickly making this type popular with T-shirt artists who can have lots of jars of colours mixed up but don’t require very fine spraying as T-shirt fabric won’t hold fine details.
0.6 mm is a bit large for our purposes. 0.5 or 0.4 mm is a good size for priming, base-coating large areas and pre-highlighting. 0.2 mm is good for fine detail work and is as small as you want to go with acrylic paints. 0.3 mm is good if you want an all-round nozzle. Note that most airbrushes can either be bought with different nozzles or extra ones can be purchased separately and that it only takes a moment to switch them over. Also note that this guide might vary depending on the airbrush you buy but the general rule is, the smaller the nozzle, the thinner and slower drying your paint needs to be so very fine nozzles are better for artists inks or watercolours and wider nozzles are better for acrylics or enamels.
Which Compressor should I buy?
Buy a compressor; don’t mess about with compressed air cans or a tyre with a regulator. You want a consistent and reliable air supply without having to keep stopping to change tyre or aerosol. Don’t buy the cheapest compressor; you’ll only end up upgrading. Get an on-demand compressor with a storage tank. If you get one without a tank then it will be on constantly while you’re spraying anyway and it will get very hot and possibly cut out when it overheats so you might as well just get a cheap one. The larger the storage tank, the longer the compressor won’t be on. Oil compressors are ideal but don’t go there if you have a tight budget or kids who’re likely to knock it over. Piston compressors are a bit more noisy but bearable. Don’t buy a Diaphragm compressor. They’re cheaper but they wear out too quickly. Spend money to save money!
Things You May Not Have Thought of…
You will need to thin your acrylic paints and retarding them is a good idea too. I use Vallejo Airbrush Thinner, which smells like airbrush cleaner and froths up like detergent (I suspect that these are some of the ingredients and are certainly things that the old airbrushing veterans use in their home made thinners). A large bottle of this will last you ages as you only need a couple of drops in each mix and the rest of your thinning you can do with water. If you buy Vallejo Model Air paints, they will still need thinning for a 0.2 mm nozzle. The only paint I don’t thin is the Vallejo Polyurethane Primer, which I put through a 0.5 mm nozzle.
I use Vallejo Airbrush Cleaner and water. Note that you will use a lot more of this than the thinner so always keep a bottle in hand. You should also get yourself some cleaning brushes (Harder and Steenbeck do a good set for not much money), a supply of cotton buds and either a needle or a nozzle reamer for cleaning your nozzles. A sewing needle glued into a stick can be handy too.
Do your lungs a favour and get a decent mask and a spray booth. Even if you survive the thinned paints, the atomised airbrush cleaner is nasty! A box of disposable gloves saves getting overspray on your hand too. Demijohn corks are also useful to mount your miniatures on whilst working. This prevents your fingers from getting in the way of the spray and stops you rubbing half dry paint off of your miniature.
This can be useful for painting larger figures or vehicles, which would be too heavy or awkward to hold for long periods of time.
Things to Look For
Gravity fed, dual action, internal mixing airbrushes with no plastic components, a paint volume limiter (a bit on the end of the handle, which screws in and out) and an air flow control are a bonus but not a necessity; a compressor with a storage tank; safety gear.
Things to Avoid
Avoid any airbrush which costs less than about £100 (unless you just want it for priming); single action and syphon feed airbrushes, especially if they’re external mixing (again, unless you only intend to use it for priming and even then, still avoid external mixing); airbrushes with plastic components; diaphragm compressors; compressors without a tank, breathing in atomised airbrush cleaner and tyres!