Air Brushing on Glass

Air brushing paint and enamels onto glass can give extremely subtle graduations of colour and tone.

Air brushing onto glass is a little different than onto other slightly absorbent surfaces. As glass cannot absorb the moisture from the material being sprayed, the medium needs to be allowed evaporate.  This means that each layer of paint must be allowed to dry before the next layer is applied.  If too much liquid is applied to the glass, it will bead up giving a stippled appearance to the finished result.

The two main media that you can use are water and alcohol.  The advantage of spirits is that it evaporates from the surface more quickly than water.  Also apply in a warm rather than cold place. You can use a hair dryer on low speed and power to assist the drying.  This will reduce the waiting time between applications.  You do not need to use any gum arabic in the mix to help it flow, but a drop of liquid soap will help to break the surface tension of the medium.  This avoids any "beading up" on the super clean glass.  

The consistency of the mix of the paint or enamel with the medium will need to be many times thinner than that used for painting with a brush. Also the air brush will need to be able to cope with the relatively large (in relation to inks and other paint) particles that make up the glass paint. This may require a little experimentation to find nozzle sizes that can cope with the glass paint particles.

Before you begin air brushing you must prepare the glass so it is very clean.  Clean the glass very well with clean water followed by isopropyl alcohol.  After this thorough cleaning and drying, use some of the paint to rub the glass. As the paint is a slight abrasive, it cleans off anything the other cleaning methods could not get off.

The paint should be applied in steady sweeps across the area to be covered at least 10cm/4" from the surface.  Start moving your brush before you switch on the paint and keep moving after you stop applying the paint.  This avoids heavy applications at the start and finish. As there is no absorption of the moisture by the glass (as there would be on paper or board), you must pause after a very few passes.  This is where the spirits show their value, as they evaporate more quickly than water, allowing you to apply the next layer sooner.

One thing you will notice is that the paint will settle within the medium unless you agitate it frequently. So you should make sure the paint is evenly dispersed within the container by agitating it before starting each layer. The movement of the air brush during application will be enough to keep the paint suspended in the medium while you are applying the glass paint or enamels.

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Because air brushing puts very small particles into the air you need to observe various precautions. You need to have a dust mask on at all times you are air brushing. You should do this in a spray booth with extraction if possible. If not, you need a well-ventilated area and very good clean up afterwards.