Welcome Guest ( Log In | Register )

Airbrushing Tutorial

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.

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.

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.

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.

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.

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.

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.

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.

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

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) .

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


The older Railmatch enamel pots with the horrible tops!!

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.




 

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

RSS    Lo-Fi Version Time is now: 23rd April 2021 - 03:26