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David Boxshall airbrush demo
13 April 2012

See more at Art Profile.

The 'dual-action gravity-fed" airbrush is a piece of precision engineering. One of them used to cost hundreds of pounds but Chinese manufacture has brought this down substantially.

'Dual action' means that a single trigger controls both air-flow (by depressing the trigger) and paint-flow (by moving it forward and back). The forward and back movement slides the very sharp central needle into and out of the nozzle, restricting or releasing the flow which pulls the paint out of the 'gravity-feed' reservoir. The further back the needle, the heavier and wider the aerosol cone of paint emitted by the brush.
David makes heavy use of stencils. His first demo used a sheet of thin card with a 6" hole in the middle. A little red/orange gouache, some water and a touch of gum arabic went into the reservoir and the stencil was taped to a piece of white paper.

He checked that the paint was flowing OK by spraying onto the stencil card itself. Then he worked continually round and round, starting outside the circle (most of the paint going onto the stencil, not the paper) and gradually moving more towards the centre. At the very end, a gentle mist over the bottom gave the impression that the ball was resting on a surface.
Airbrushes lend themselves to almost any type of paint, provided it can be thinned to the consistency of milk. David favours gouache but also uses ordinary watercolours, Liquitex acrylic, various inks, including Indian, ordinary Quink, and some specialist ones like Dr. Martin's.

The choice of support is not critical - it depends on what you want (paper, card, metal, cloth . . . ).

The paint dries almost instantly because the aerosol droplets are so minute and it is applied so gradually.

Of course you have to clean the brush out each time you change colour (spray water through it) and give it a more thorough clean at the end of the day. This is particularly important if you are using cellulose or acrylics, paints that set hard.

David had been working with airbrushes since the age of 8 (when he started decorating custom cars) but the techniques were a mystery to most of us.
The dual action trigger allows single finger control of the spray itself but distance is another important variable. There is always virtually invisible overspray and so if the stencil does not cover the entire sheet of paper you need to mask the outside.
For a pyramid, done in black Quink, neat, he used four stencils: one a cut-out kite-shape outline, one for palm trees, one made by roughly tearing a bit of newspaper for the skyline and one which was just a small circle of card.

He masked one half of the pyramid with an extra scrap of card and, as before, starting spraying onto the stencil itself and working in towards the paper. The other face was done in the same way and the stencil removed. The trees and skylines were similar, giving David control over where the shadows were. Finally the circle of card masked the sun as he sprayed back and fore over the sky.
For more complicated (realistic) images most of the work goes into creating the stencils.
Working them out, all on tracing paper, really is a lot of work.
He had made a line-drawing of a rose, clearly distinguishing wherever there were to be sharp changes of tone. He had coloured the drawing not with realistic colours but to find how many separate stencils would be required (remember the well known 4-colour map theorem). Using punched-out locators to make sure that successive stencils were consistently aligned, he had traced and transferred these lines onto a series of cards and carefully cut the shapes out with a scalpel.

As was now becoming obvious, his airbrush technique relies to get tonal variation by spraying near the cut-out edges of the stencil so that only minute amounts of paint build up gradually in the cut-out areas. The colour variation here was due to residual black from the pyramid example.
Interesting effects can be made on black paper.

A stencil of 4 intersecting lines, perhaps a millimetre wide, and some white paint, gave this bright star effect by spraying in the centre and moving the airbrush only enough to get overspray out along the rays.
The smaller stars began as touches of paint from a paintbrush handle but each was brought to life by a brief spray of white (for which you need experience!).
Another technique, described, but only illustrated in passing, uses low-tack transparent masking film:
Draft the detail on tracing paper
Clean all traces of grease from the board
Transfer the drawing onto the 'virgin' board
Cover the drawing with low-tack masking film
Carefully cut the film along all the lines (scalpel)
Peel bits of film off, one at a time, paint the exposed surface and replace the piece of film.
Since the paint will make the film opaque I guess this means that the original sketches must have enough detail for you to know exactly what is to be painted in each area.

Other little asides:
He runs a small extractor fan over his board at home
Liquitex is particularly good on cloth, food colour on cakes
Airbrush can create interesting backgrounds for conventional paintings. Texture effects come from crumpling paper, spraying obliquely and then ironing flat again.
Finally, David asked for someone to try an airbrush for themselves. Angela shouted first.
You could see the rapid progress she made from tentative squirts to confident strokes.

So ended a most interesting and unusual evening. Thank you, David.
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