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by Peter Morgan

Airbrushing is one of those things that
beginners find daunting. The investment needed often makes it the most expensive
tool on the bench and the fear of getting the wrong one is often off putting. I
have written this tutorial to try and help some of those newcomers take the
leap.

I don’t believe there is a right or wrong way of airbrushing. But having
achieved consistently good results for several years I do feel that I can speak
with authority on what works for me. Hopefully not just making recommendations
but also listing why I have made the choices I have.

I have tried to keep things simple, but I have gone into detail where I think it
is justified. I have done my best to explain not only what I do, but why I do
it.

I have given an explanation of the different types of airbrush and air supplies
and well as giving the full process of spraying a carmine and cream coach from
scratch to the finished product.

There is no single tool in this article that will enable you to make a perfect
paint job. All the items work together to give a good finish.

Contents

Part 1
Equipment


Choosing an Airbrush

Air supply

Hoses and moisture

Pipettes and post and stuff

Paint

Colour accuracy

Paints available to the UK modeller

Paint - Back to basics

Part 2
The painting process (soon to follow)


Surface preparation

Paint preparation

Thinning

Stages of paint drying

Lining

Bow pen

Bob Moore pen

Part 3 Spray painting - the process (soon to follow)

Two-tone coach - Blood/Custard

Weblinks

Part 1 Equipment

Choosing an airbrush

There are several different types of airbrush. Internal mix, external mix,
single action, double action. I have even come across a couple of “rotary”
airbrushes from the 50's!

Internal and external mix airbrushes are exactly what they sound like. The
external mix airbrushes blow the air across the top of a tube containing the
paint. If you have ever sat in a restaurant and blown air across the top of your
drinks straw and blasted your friends and family with lemonade then you were
basically being an external mix airbrush. There are very few of them about these
days but you can usually pick them up in DIY shops for about £10. Unfortunately,
while there are one or two good ones, the paint spray is very inconsistent. Its
very difficult to get an even spray from them. The vast majority of airbrushes
including all the ones that I am going to mention in this article are internal
mix.

Examples of external mix airbrushes.
Air gun Trigger Gun barrel Shotgun Gun accessory


Liquid Bottle Drinkware Fluid Plastic bottle


The next and probably most important distinction is single action or double
action.

With a single action airbrush you press the button and the more you push it the
more paint and air comes out. You don’t have any control over the air:paint
ratio.

Single action airbrush.
Revolver Wood Gas Tool Bicycle handlebar


With a double action airbrush you push the button down to determine your airflow
then ease it back to get the desired amount of paint. This sounds quite tricky
but is actually very easy and has several advantages, I will talk about a couple
of them later but a quick one that I will mention here is that you can use the
airbrush to give you a blast of pure air with no paint. If for some reason you
want to dry something very quickly then this is ideal.

Many modellers use a Badger 150 or 250. Usually because they had it recommended
to them. They are good airbrushes and there is really nothing wrong with them.
But they are also old fashioned airbrushes that are difficult to disassemble and
clean compared to modern airbrushes.

When I first went to buy an airbrush, I immediately went out and looked at the
prices and the features and bought a Vivaz double action airbrush. They can be
seen in many shops under several brands but they are all the same airbrush. It
came with a 1 metre thin plastic hose and a couple of bottles and in the packet
it looks great!

I got home and plugged it in and it worked great too! - for the first couple of
minutes! The airbrush is designed for blowing ink and for that purpose it would
have been perfect. Unfortunately, as with many of these Chinese copies, the
quality of the tool is very poor. For a start the spring on the air valve was
far too soft. It was either on or off, I had no real control over the amount of
air. Secondly, the paint cups on these airbrushes are only a push fit and the
bottom of the airbrush had not been machined well enough before chroming and so
the cup was always in danger of dropping out. Lastly, the airflow over the
needle was so poor that it quickly developed a crust that gradually increased to
the point where it either completely blocked the airbrush or would blow out all
over the model completely ruining the finish.

After that fiasco I splashed out on a Badger 155 Anthem.
Musical instrument Rectangle Musical instrument accessory Guitar accessory Wood


Musical instrument Rectangle Font Metal Musical instrument accessory


I think its fantastic and currently the best airbrush available for our work.
Apart from being beautifully made, it has several features which make it
perfect. I liked it so much I bought a second one! Here's why:

It has a double tapered needle so when you ease back the lever to increase paint
flow, first it acts as a very fine airbrush for detailed work then as you
continue to ease it back, the second taper kicks in and it becomes much courser
for doing larger work. This eliminates the need for the several interchangeable
needled for the older 150 etc…

Close up of the double tapered needle.
Writing implement Cosmetics Office supplies Pen Font


The bottom feed has an interchangeable colour cup for detailed work or a larger
paint bottle for doing those big jobs like painting track.

Everything is finger tight. There are no need for fiddly wrenches and no danger
of over tightening anything.

The self centring nozzle virtually eliminates alignment problems between the
needle and the nozzle.

Because the paint we use is much stickier than the inks the airbrushes were
originally designed for, I generally have to strip the airbrush down after each
use and give it a really good clean. The Anthem can be stripped down in 20
seconds flat as there are far fewer parts than on other airbrushes and thus less
to go wrong.

Air supply

The air source and the hose are just as important as the airbrush itself. They
work together to give a consistent and smooth flow of air to the airbrush.

There are many ways to get air to the airbrush and they all have their positives
and negatives.

1. A can of compressed air. The easiest form of air supply is simply a can of
compressed air. You can buy them in your local model shop for a few pounds. They
are small and very portable. So if you are after something to go in the tool box
to take to an exhibition then they are ideal. They do have some drawbacks. As
gas decompresses it cools. This is a problem for us because it causes
condensation in the hoses and also cools the paint. The pressure is not
consistent. As soon as you start to use the can the pressure in the can starts
to reduce. This is especially a problem with the smaller cans. Of course they
also run out. The last thing you want to happen during a paint job is to run out
of air half way along a coach side. Consistency is key and an interruption to
the work is really the last thing you want.

Liquid Drinkware Fluid Tableware Plastic bottle


2. A car tire. As this is a larger reservoir of air than the can it will provide
a more consistent flow. But the lower initial pressure means it will not last
any longer than the can.

3. Gas cylinder. A cylinder of Co2 is sometimes used these days. But I
personally would feel uncomfortable having a large cylinder of compressed
anything in my home. A can of deodorant, if it gives way (for example left in
the sun), is easily enough to remove the roof from your house.

4. Compressor. The only air supply I would recommend. They come in several
flavours but they tend to either be cheap diaphragm compressors or more
expensive pump compressors. Either are perfectly acceptable as long as there is
a reservoir of air between the pump and the airbrush (more on that in a moment)
the down side is the initial outlay. Mine was a cheap compressor at £60. But
it's very noisy. The silent compressors are generally at least twice that. Some
compressors come with a reservoir and some don’t.

Brown Rectangle Wood Packaging and labeling Carton


I am looking to upgrade my compressor. I am very happy with the one I have
except that it is very loud and I want something more wife friendly.

Hoses & Moisture

If the compressor has a reservoir then if you really want to, you can make do
with a cheap hose, but if it doesn’t then a decent long hose is a must. The
amount of air contained within the hose acts as a reservoir and provides a
cushion from the pulsing compressor. My compressor may have only been £60 but I
had to spend another £20 on a long braided hose to get rid of the pulsing.

A decent hose makes the task of airbrushing far more enjoyable. A good braided
hose hangs straight from the airbrush (instead of curling up) and allows you the
freedom of movement that you need.

Electrical wiring Gas Cable Wood Audio equipment


A very cheap hose showing the curling problem. it gets very annoying when you
are trying to paint a decent model. it feels restricting and constantly pulls on
the airbrush.

Material property Font Circle Event Electric blue


My air hose. its a badger hose with a thick
rubber pipe and a braided outer covering. Its very flexible and allows far more
freedom than the cheap plastic hose.

Moisture is a real problem for airbrushing. As gas/air decompresses the moisture
is brought out and forms water droplets. If they end up going through your
airbrush and onto your model then the finish will be ruined. With my own
compressor, I have never used a moisture trap and I have never had a problem.
BUT I have used a friend's compressor and experienced terrible problems within
about 30 seconds of starting the job. My advice is to get a compressor with a
filter. If you do get problems then the filter will take care of it. If you
don’t then it won't do any harm. I would rather spend an extra £30 on a filter
than ruin a loco spray job.

Pipettes and pots and stuff

Wood Office supplies Rectangle Font Beige


Keeping things clean is one of the keys to a good finish. If you are going to
the trouble of buying a kit at considerable expense and investing all that time
in building it and buying an airbrush and compressor and hose then for goodness
sake, use a fresh cup for your paint. They cost 5p! It's just not work the risk
of contamination. The same goes for the pipettes.

Colour accuracy

A few times I have heard someone say something along the lines of “I remember it
being darker than that”.

The human being is not capable of retaining accurate colour information. This is
a fact and has been proven many many times over.

On top of this there is the issue of weathering. As soon as a coach leaves the
works and is subjected to sunlight the colours start to fade. For a while
Southern EMU’s had triangles painted on the one end to denote the end with the
luggage compartment. They were actually orange. But faded in just a few weeks to
yellow and before long they were white. So what colour is correct?

The environment that a colour is viewed in makes a huge difference to the colour
that appears to the human eye. In the case of paint, we actually see the light
that is reflected off the surface and enters the eye. Different pigments reflect
different wavelengths of light.

A red pigment reflects longer wavelengths than a blue pigment. To complicate
this even further, different light sources put out different spectra or
varieties of light wavelengths. The sun outputs the all wavelengths in the
visible spectrum. An incandescent bulb puts out wavelengths predominantly in the
yellow region and a neon strip light puts out wavelengths in the blue region.

So if you look at the same model under two different lighting conditions you
will see a huge variation in colour.

Now for the bit that older folk don’t like very much… eyes get older. The eyes
that you saw a train with when you were ten years old are not the same ones that
you are now looking at your model with 60 years later. They have 60 years of
weathering and wear and tear on them. They have been affected by the things you
have eaten and the drugs you have taken and the things you have smoked…..

My advice is just to trust the experts. A huge amount of research goes into
producing a colour of paint. For early stock there is often no actual paint
sample to work from so we only really have a best guess anyway. For more recent
colours it's easier because we have the pantone numbers to work from or we know
the exact recipe for the paint. For example, I am sure we have all seen
paintings and films and pictures of the Titanic. Nobody really knows what colour
the funnels should be. We know they were painted “white star buff” but nobody
has a paint sample of that colour, some experts think it’s a yellowish shade and
some think it should be more of an orange and there are some that think it
should be brown. We don’t really know. All we can do is take a best guess. I
have a few paint chips tucked away. I have a BR blue and a royal claret. But
that’s about all. But there are people who collect paint chips and provide us
with an invaluable resource. Sometimes the original works samples still exist.
For example the paint samples from Swindon of loco green and the samples of red
and blue for the LMS Coronation locomotives.

My advice is to just trust the experts, they do this sort of thing for a living.
I have taken issue wit’s a couple of colours though.

Not every colour is perfect. I am very careful with the buffer beam reds. Some
of them are, in my opinion, too orange. Humbrol white sometimes comes out a
ghastly beige colour.

Paints available to the UK modeller

We are very lucky in the UK. We have a couple
of companies selling really great paint for our models.

Humbrol (part of the Hornby group of companies and formerly part of Airfix)
sells a range of railway colours. I have not used them yet and so I can't
comment on accuracy. I find some Humbrol colours spray very well while others
tend to separate out in the pot and spray very inconsistently (especially grey
colours) .

Tin Font Paint Ingredient Cylinder


Railmatch have been in the business a long
time. They used to sell enamel paints in jars that I hated. After a couple of
uses the paint would harden around the thread on the lid and I was forever
throwing away jars of paint that were ¾ full. Since those days the company has
come on a lot. They have switched from enamel paints to selling Acrylics (more
on that later). Generally they are accurate. Although I do have question marks
over a couple of their colours.

The new acrylic Railmatch paints
Ingredient Medicine Bottle cap Liquid Service


The older Railmatch enamel pots with the horrible tops!!
Mason jar Liquid Writing instrument accessory Font Solvent


Phoenix Precision Paints. Generally these are
the only paints I use. But they are not the easiest. They are very professional
paints and you do need to follow the instructions very carefully. The colours
are generally accurate. Although, as with Railmatch I do have question marks
over a couple of them.

Tin Tin can Paint Fluid Aluminum can


Paint - Back to basics

Paint consists of 3 parts. The binder, the pigment and the matting agent (there
be some more in there but those are the ones I worry about)

Binder - this is the glue that holds the other 2 together. Gloss varnish is
simply binder on its own. No pigment and no matting agent. If you add the
matting agent you get matt varnish. Add the pigment and you get paint!

Pigment - as the name suggests this is the bit that adds the colour. The pigment
particles are minute. They are ground in between metal or glass balls and a good
paint is nice and smooth. To put this into perspective, if you buy cheap shampoo
you will find that it feels a little grainy or feels like it has small fibre
strands in it. This has only been mixed by what is basically a large blender.
Spend a couple of quid on the decent stuff and it feels far smoother, this has
gone through a proper mill.

Matting agent - Most enamel paint is naturally gloss. To make it matt, they add
a matting agent. You can buy it separately but be careful, a little goes a long
way! It's good fun to experiment using different amounts. You can get different
levels of gloss and satin and matt depending on how much you add.

Part 2 & Part 3 to
follow...


Weblinks

Small disposable cups used for mixing paint ready for
spraying. 30ml calibrated
beaker.

Available from Alec Tiranti, 10p each. Code 409-110-
www.Tiranti.co.uk

Pipettes. Available from Freestone Model Accessories. Don’t know the address for
their website but the are available on 01993 775979 as well as attending most
major exhibitions.

Paints
Rail match -
www.railmatch.co.uk

Phoenix Precision Paints - www.phoenix-paints.co.uk

Humbrol - www.Humbrol.com

Airbrushes
Badger - www.badgerairbrush.com

Iwata -
www.iwata-medea.com


November 2009

 
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