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Choosing an Airbrush or Spraygun

This page is designed to help you decide what type or size of airbrush or spraygun you require to paint the type or size of model you are making.

One of the questions we are commonly asked is ‘Can I spray your paint?

If So

What equipment do I need,

How much will it cost?

And can I use aerosols?’

In order to answer these questions we need to pose some questions of our own:-

Why do you need to choose the equipment you are going to use?

Can’t I just choose something based on price?

Can I use aerosols?

Whilst the questions are relatively simple the answers are a little more longwinded.

Why do you need to choose the equipment you are going to use?

To answer the question we need to ask a question:-

what do you want to use the equipment for?

Any decision regarding the purchasing of spraying equipment MUST be based on the type of work you intend to do with it.

As an example a superfine airbrush capable of producing a 1mm line would be totally unsuitable for a 5” gauge live steam model,
and in the same respect a spray gun suitable for a 5 ”gauge model would be overkill on an N gauge model or a figurine.

 

Having decided on what you are going to use the equipment for you can then start to make a choice regarding the type of equipment

You may find that you will actually require more than one piece of equipment, particularly if you model in more than one scale or discipline.

Can’t I just choose something based on price?

Again to answer this question we need to ask the questions what do you want to use the equipment for and how experienced are you?

Yes you can buy the cheapest airbrush you can find, but what materials do you intend to use it with and what result do you expect to get?

The cheaper the equipment the less likely that the amateur is going to get good results with it. 

Can I use aerosols?

Aerosols can be used but remember that an aerosol is very similar in design to a fire extinguisher – either on or off. As such they tend to be very good for certain types of job but useless at others. For example - they are very good at laying down a basecoat, primer or for putting a varnish coat over the top of a finished model.

Types of equipment.

We have very basically covered whether you choose an airbrush or a spray gun, but to allow a better decision we need to look at the spray pattern differences between spray guns and airbrushes.

The average basic but good quality airbrush will have a spray pattern of between 1.5mm (1/16”) and 50mm (2”) depending on the model, whilst a spray gun will go from about 6mm (1/4”) to 150 - 200mm (6 – 8”) again depending on the model.

Choosing an airbrush.

Before you even think about buying an airbrush it is worth remembering that an airbrush is essentially an artists tool that is designed for the application of inks, whilst paint is basically an ink it is far thicker than ink and therefore requires far more thinning to make it flow effectively.

This thinning of the paint to allow it to flow depends on the type and quality of the airbrush – the better the quality of the airbrush the more you will have to thin to get the paint to flow, this will result in very thin coats and thus the need to apply a number of coats to get a decent finish.

There are two basic designs of airbrushes. -

Internal mix and external mix airbrushes.

 

External Mix Airbrushes.

Most of the very cheap airbrushes are of the external mix type, that is there is a nozzle for the air and a nozzle for the paint. The action of the air passing over the paint nozzle causes the paint to be drawn up from the bottle, vaporised and then to the surface being painted.

By dint of its design all external mix airbrushes are single action, this means that you have one button that you press to allow air to exit the air nozzle, this usually has very little, if any, controllability – control of the air being achieved by controlling the supply to the airbrush.

Control of the paint supply and the amount that you actually apply to the surface being painted is by screwing the paint nozzle up or down, this cannot be done whilst you are spraying.

External mix airbrushes are fine for certain types of paints and inks but can cause major problems when used with specialist materials such as etch primers.

 

Internal Mix Airbrushes.

Internal mix airbrushes are of two basic designs

– suction feed or gravity feed,

and two sub designs, single action or double (twin, duel) action.

SP50 Suction Feed Internal Mix Airbrush The suction feed uses the same basic design as the external mix in that the movement of air sucks the paint into and then vaporises it inside the body of the airbrush.

The gravity feed type is similar in design but instead of the paint being sucked into the mixing chamber it falls from a cup on top of the body of the airbrush.

Neither type is any better or worse than the other but they are designed for different jobs.
The cup on a gravity feed airbrush will hold probably 10ml of liquid maximum, whilst this will be fine for painting a small N gauge locomotive or for work on a figurine it will require refilling, possibly many times, to paint a 4mm (OO) or larger model.
The suction feed type is only restricted by the size of bottle you can get to fit it. A possible major flaw with a suction feed airbrush is the amount of liquid required.

When preparing paint for a suction feed airbrush you will always need to mix more than you require because you will always be left with an amount in the bottom of the jar – this does not happen with a gravity feed airbrush.

The two sub designs of single or double action can apply to either main design.

The single action is similar in its application to the external mix airbrush in that pushing down the button releases air into the mixing chamber
which vaporises the paint in the chamber and then directs it towards the surface being painted.
 

The difference is in the nozzle / needle arrangement. Where the external mix brush has a nozzle that is purely designed for air and is therefore a hole, the internal mix brush has a nozzle into which a needle is designed to fit it is this nozzle / needle arrangement that controls the flow of vaporised paint to the surface – the bigger the gap between the nozzle / needle the more paint is released, the smaller the gap the less paint.

Control of this gap is achieved by adjusting a screw at the rear of the brush which moves the needle either in and out.

The double action brush is essentially the same with the nozzle / needle arrangement, the main difference is that the needle is controlled by the same button as the air.

Pushing the button down releases the air and pulling back draws the needle out of its housing in the nozzle thus allowing vaporised paint to exit and make its way to the surface.

Whilst the double action brush is far more controllable than the single action it does require far more practice and skill.

It is far too easy to open the nozzle on the double action and deposit an unwanted amount of paint slap bang in the middle of a nicely painted surface and cause a problem that will take a lot of sorting out, than it is with the single action.

There is a third design that is a cross between the suction feed and the gravity feed type. This type has the liquid inlet at the side of the airbrush and is usually supplied in a kit with both a gravity feed cup and a suction feed bottle.

Whilst this design may seem the best of both worlds but they are invariably designed with fairly fine nozzles and tips which will restrict the flow of the material being sprayed unless it is thinned quite considerably.

Other factors to be taken into account when choosing an airbrush is your experience together with the type and size of model being painted.

It is no use, for instance, trying to paint a 3 ½” or 5” gauge model with a gravity feed airbrush that will only take 10ml of liquid maximum.

On the other hand it would be perfectly suitable for painting a 2mm (N Gauge) scale model or even a 120mm figurine.

 

Phoenix Precision Paints stock a small range of airbrushes, and we can give advise on which would be the best one for your application.

For model engineers who whishes to paint a 3 1/2" or 5" model we would recommend the Badger 200. This is a extremely good and basic airbrush that is perfectly suitable for most types of model railway applications and model engineering applications up to and including a small 5” gauge model.

Whilst we do not stock them Badger do a range of about 5 or 6 other airbrushes from a very basic model up to a top end model at over £200 (2008 price).

Two other ranges of airbrushes that are worth looking at are Iawata and Aztek.

Both ranges have very good reputations but tend to be more expensive than Badger.

The Astek range are unique in that they have an interchangeable head unit that allows the user to quickly and simply change the nozzle/needle and hence the spray pattern, personally we do not have any experience of the Astek range and can only go on their reputation.

The Iawata range is based on conventional design and has a very high reputation and a good range of airbrushes.

We have used Iawata products and were very impressed with them.

We would have to say that the particular model that we have used, whilst extremely good for railway models up to 4mm:1 foot (OO, EM, P4) and the smaller military and aviation plastic models, it might struggle with anything larger.

Other ranges of airbrushes are available.

 

Choosing a Spray Gun

Spray guns are generally commercial tools designed to apply paint over a larger area than with an airbrush.

Like airbrushes there are 2 basic types of spray gun and a two sub designs.

The first type is the conventional type of spray gun – this is what most people are used to, and is the closest in design and use to an airbrush.

Conventional spray guns are designed to work at pressures of between 1 bar (approx 15 psi ) and 4 bar (approx 60 psi ), and with an air consumption rate of between 2.5 and 8 cfm dependent on type.

Various additional features can be found on spray guns that are not normally on an airbrush –

Fan control – some spray guns allow you to direct air at the sides of the paint cone as it leaves the nozzle, this has the effect of turning the cone into a fan. The ring that controls this function can be rotated so that the fan can be horizontal, vertical or any angle in between.

Air Volume Control – This is a very useful feature – it allows you to reduce the flow, or volume, of air through the gun BUT without reducing the pressure.

 

Two basic designs of conventional spray guns are available - suction feed and gravity feed.

The way they work is identical to the internal mix airbrush but on a larger scale.

Like an airbrush the conventional spray gun delivers a minimum amount of paint onto the required surface at a reasonably high pressure.

Suction feed spray guns suffer from the same problem regarding quantity of liquid as the suction feed airbrush.

The gravity feed version does not have the same problems,

Cup sizes tend to start at 0.25 litre (approx 3/8 pint) and go up to about 0.75 litre (approx 1.2 pints)

 

Phoenix Precision Paints generally only stocks one spray gun the Kite mini spray gun.
This is a very nice gravity feed conventional spray gun that in our opinion out
performs similar guns two or three times its price.


 

 

 

 

 

 

 

 

 

 

 

The second type of spray gun is the High Volume Low Pressure (HVLP) type of gun.

This type of gun is designed to apply large quantities of paint at very low, 0.5bar (7.5 psi ) or less.

This type of spray painting is how the majority of cars are painted.

It is totally unsuitable for small scale modeling.

There is some possibilities of it being used for larger scale model engineering projects, but before you go down the HVLP route think about the following:-

You will need to have an enclosed space, complete with extractor fan.

A decent face mask and probably an enclosure suit.

Paint and thinners – HLVP will use at least 4 –5 times more paint and thinners than conventional spraying.

Etch primers can have problems with HLVP equipment.

 

Phoenix Precision Paints DO NOT recommend HLVP for any type of model work. In our opinion the problems associated with the process far outway the positives even if we could sell 4 times the amount of paint.

 

 

All information on this page is provided in good faith, whilst all information is believed to be correct Phoenix Precison Paints Ltd can accept no responsibility for incorrect information on this page.

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