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Thread: Airbrushing - Air Pressure & Compressors

  1. #1
    Join Date
    Jan 2008
    Location
    BC Canada
    Posts
    15,056

    Default Airbrushing - Air Pressure & Compressors

    Ahhh compressors.
    Don't buy cans of compressed air, for the price of 7 cans of this junk you could own a cheap compressor. The good news is that you can do this on the cheap in alot of cases.
    I have a few options that I use for this also.

    But first let's talk ...
    AIR PRESSURE
    Found some good descriptions online.

    There is no such thing as an exact pressure for any paint, airbrush, or situation.

    Think of airbrushing as washing your car with a hose. Get up close to the car and turn the hose on at full pressure and what happens? Most likely you are going to get wet. When you get in close for the tight areas you have to lower the pressure to prevent a lot of overspray. Likewise if you get way back from the car and try to wash it with low pressure the water doesn't even get there, so you need more pressure.

    Using an airbrush is not that different from the analogy above. When you are in close to the surface you need to use less pressure to prevent overspray. When you are farther away from the surface you need more pressure just to get the paint to the surface of the model. In the case of an airbrush though, even at low pressure the paint wil eventually get to the model's surface. The problem is that if it travels a good distance through the air it will dry, or partially dry, during the time it takes to get from the airbrush to the model. This causes a dimpling of the paint surface commonly known as "Orange Peel".

    The overall goal of using an airbrush is to get the paint to the surface, and there are four things that affect how well that happens:
    1. The construction and type of airbrush. Some airbrushes atomize or pick up paint properly at lower pressures than other airbrushes. Siphon feed airbrushes usually need slightly more air pressure to feed reliably than gravity feed brushes will. Internal mix airbrushes will generally atomize paint better at lower pressures than external mix airbrushes will. This factor also includes the size of the nozzle and needle in the airbrush. Some airbrushes have tip assemblies or separate nozzles and / or needles that can be changed, some have a single combination.
    2. The viscosity, or thickness, of the paint. If you try and suck molasses through a soda straw you are going to have a much harder time than you would sucking water through the same straw. Many people think this is the only reason for thinning paint, but it isn't.
    3. The volume and pressure of air through the airbrush. Given enough pressure and volume you can get molasses through a soda straw, but it takes quite a bit.
    4. The distance between the airbrush tip and the surface of the model.
    You cannot change the basic construction of the airbrush, other than perhaps changing the nozzle and needle, but you can change any of the other three factors. To complicate matters, these factors frequently change while you are painting. The thinner in your paint will evaporate causing it to be more thick, you will move your hand closer to or farther from the model's surface, or your air pressure may change because of temperature changes or when the motor cuts on and off.

    Pick a pressure that you want to use for painting and then thin the paint enough so that it atomizes and flows through the airbrush properly and covers the surface well at that pressure. Knowing what pressure to start at is something that comes with experience and knowing your tools. A good starting point is 15 to 20 psi. For painting models you should never need more pressure than that. You can get excellent results at higher pressures, but you'll get alot more overspray...mess and waiste of product.

    Keep in mind that there will be a minimum pressure as well. Airbrushes "Atomize" the paint and then mix it with air. Each airbrush has a pressure at which atomization is the best, and this is the point at which you will get the finest spray pattern (not necessarily the narrowest spray, but the particles of paint are as small as they are going to be). This is usually around 20 psi for most airbrushes, but will very with the paint and other factors. At this point you should get the smoothest finish, so it worth experimenting to find that point for your equipment and paint.

    If you are spraying a large area with a single color, such as the main color of a car, tank, airplane, or ship, then you can use a relatively high pressure (say 20 psi), leave your paint somewhat thicker, and get good coverage with each pass of the airbrush. If you are painting a critical area, such as the demarcation between colors, you will have to reduce your pressure dramatically to prevent overspray from causing a wide line. When you reduce the pressure you are going to have to thin the paint more to get it to flow. You will additionally need to get much closer to the surface which in turn requires slightly thicker paint to prevent the air pressure from the airbrush from blowing it around. The bottom line is that YOU will have to find what works for YOU under specific circumstances.....PRACTICE ON YOUR LEXAN SCRAPS!

  2. #2
    Join Date
    Jan 2008
    Location
    BC Canada
    Posts
    15,056

    Default

    With the above being said I spray from 15psi to 35psi depending on the application.
    In most cases these days my projects are much smaller than the old automotive stuff I've worked on. The need for high capacity/professional grade compressors just isn't there.

    You have to ask yourself how often and what other applications will this be used for. In my case I only use them for airbrushing, blowing up the odd tire and blowing dust and debris out of projects.

    I run two types of compressors for my stuff, both are under $200
    1. Portable dedicated Airbrush compressor.
    • Compact and lightweight (great for mobile jobs or even small space applications like condos and apartments)
    • Most are Oil-less diaphragm design Never needs lubrication
    • Tankless
    • Many advertize to be scilent or quiet but this depends on if you can keep it from vibrating on whatever surface it sits on.
    • Provide a smooth steady pressure from 15psi and up (this depends on price and quality)
    Prices for these varrie but start from around $60 +, a medium quality portable would be between $150 - $200.

    2. 3 gallon compressor Campbell & Hausfeld (Canadian Tire)
    • 3 gallon compressor
    • 2-in-1 2" brad nailer/stapler
    • Also includes: hose, nails, staples, oil, plugs, wrenches, inflation nozzles and other accessories
    • Built in pressure regulator
    • Even includes a few fittings that will usually attach to most airbrush hoses.
    I paid $89 when it came into the local flyer, now it even comes with a brad nailer.
    It keeps up for almost all of my small jobs in the shop. It's a bit noisy but heck...it's a shop, turn up the tunes.

    *Important note. If you're only spraying waterbourne paints like Faskolor it's not necessary but...If you're spraying enamels, laquors or any other thinner reduced paint be sure to use a set of water traps. This will prevent condensation inside your compressors tank and water lines to contaminate your paint.

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