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Airbrush Problem Solving

At the April meeting Tim kindly put together the following talk to help out those of us who are struggling to get the best from our air brushing. After a brief introduction, we were soon engrossed in the mystic world of the air brush. Most important of all is to be aware of the health impact of working with air brushes. Always wear a suitable mask, if required, when working with solvents and cleaning agents, and always work in a well ventilated area! Modelling is fun, a trip to the hospital with lung problems is not to be on the list of things to do! 

When you are going to move on to, or obtain a replacement air brush, then the first question to be answered is what do you wish to achieve with the air brush? Depending on what subjects you wish to work on will indicate which type of air brush you require. Single action air brushes are basic, but sound, if you’re looking to apply single colours or cover large areas. You obtain your control of the spray effect by controlling the amount of air flow through the brush. Double action air brushes offer a greater span of usage, as you can control both air flow and paint flow as separate items. This affords better results on more intricate projects but requires practice to perfect the use of the brush. Having said that, not all brushes are the same and you are advised to ask around you modelling friends to find out how they achieve specific results. As with all skills, practice makes perfect! The more you work with your air brush, the more you will become accustomed to how it works. 

Following on, the next problem is paint! Although acrylic paints are great for quick results, (because of their quick drying properties,) the price to pay is that they are not the best paint to put through an air brush. Because they dry so fast they can quickly upset the delicate balance between a functional and non-functional air brush, simply because of the build up of dry paint in the nozzle and on the moving parts of the brush. Enamel paints are by far the safest option but with the extended drying time this can dramatically slow down the speed at which you can work. Because the pigments in the enamel paints are ground so fine, they are less prone to build up on the surfaces of your brush and as a result, are easier both to work with and to clean up after. When thinning the paint, regardless of type, always use the correct medium as trying to substitute a thinning agent could ruin you hard work in building the model! Once again, each project is different, so how much you thin the paint is dictated by the job in hand and also by the individual. As a general rule, for most basic spraying then the consistency of milk is about right, however if the job requires a wash or shading then it is okay to thin down to a much weaker percentage. Bear in mind that the thinner the paint, the easier it will be create runs in the finish! What ever you are doing, the biggest single problem is getting the balance between the mix of the paint right. 

Another common problem is the build up of water in the air supply. By compressing the air taken into the air brush, this causes the water present in the air to condense and collect in the air tank and the hose. There are various water traps available, these work by forming a favourable area for water to collect and are designed with a relief valve or drain point to allow the user to periodically remove the water and thus prevent the paint finish from contamination by droplets drawn through the air system and delivered to the air brush by mistake. 

Compressors. There are many different types of compressors available, some with the necessary skills even build there own from redundant fridge parts! Depending on budget as well as what you wish to be able to achieve you can choose the best to suit your needs. Each type of compressor comes with its advantages and disadvantages; however they are infinitely cheaper in the long term to power your air brush than the can propellants that are available. Once again, ask around your modelling friends to gain a different but balanced opinion before making your choice. 

Having covered the two most common paints used by modellers, most liquid substances used in the hobby can be put through the air brush; the problem is how to clean out the brush afterwards. This brings us nicely on to the subject of cleaning and maintaining the air brush. Once you’re at the point of finishing the spray work, care must be taken in cleaning the air brush before putting away. The advice is always to clean out the paint holder and feed route with the appropriate cleaning products. Wash through after with clean thinners to clear any remaining cleaning solutions. By doing so you’re preventing the build up of paint debris in the air brush and this in turn could block some or all of the air holes in the nozzle and affect the function of the air brush. Equally, build up of dried paint can also damage the needle or the guide hole that the needle seats into, again affecting the performance of the brush. If you ever need to remove the needle from your air brush, do not be tempted to draw the needle through the brush, or push the needle back into the body of the brush from the back. There are numerous parts inside the barrel that could either bend the needle or damage the point, once again affecting the operation of the air brush or damaging the working parts permanently. A majority of problems encountered in airbrushing are down to inadequate cleaning. By ensuring that you carry out thorough cleaning and good maintenance you can eliminate quite a few problems before they even arise. 

To achieve good results, good preparation of the subject can be vital. By cleaning the item to be spray you remove any grease, releasing agents or other contamination on the surface, thus giving the paint a good surface to adhere to. By spraying on a primer coat, this will show up any deficiency in the surface of the model. It also provides a consistent surface for the paint to be applied to as well as sealing any porous materials like resin or plaster. The primer will also act as a barrier to protect the plastic of the kit from corrosion by cellulose based products. 

When working with an air brush, ideally you should try to find which paint type and manufacturer you prefer, and stick to that one. Saves on having loads of different cleaners, thinners etc and also you get used to that particular product range and how it works for you. Whilst you are spraying, by starting each pass of the air brush off the model and continuing the movement of the paint spray beyond the model, will help produce a consistent result to the finish once the paint has dried. This is only of use if the colour spread is across the width of the model, however if the colour scheme requires a mottled effect, then try adopting a posture which allows you to keep the air brush stationary and move the target area of the model according to where the paint needs to be applied. By knowing exactly where the paint will land you can judge where the particular part or area of your model needs to be. When spraying, try to mist on the colour in a number of coats, rather than the one thick coat approach. This will go a long way to preventing unsightly runs in the finish and also help to prevent the obliteration of detail on the surface of the model under a deluge of your favourite colour! Equally, don’t get too far away from the target, especially when working with acrylics, as the paint will dry before it reaches the model, effectively covering the model in paint dust that will spoil the finish if then covered with a fresh coat, the dreaded orange peel effect! 

One of the advantages of the air brush, depending on type, is the ability to create different effects by varying the air pressure. For general use, approximately 10-15 psi will suffice, to spray fine lines, reduce the pressure to <10 psi. Other effects can be achieved by controlling the air flow or varying the air flow during spraying. As with all things in the modelling world, practice brings experience. With that, you will be able to judge how you as an individual can create the results you desire using not just air brushes but all the different tools and techniques that go together to make for an interesting hobby. 

Hope you find this of use, if you are still unsure or nervous about any aspect of air brushing, please ask among you model club friends. We all enjoy the hobby, and part of the club mantra is to encourage and assist those that would like a bit of help.