November 4, 2012

Shake, baby, shake!

Most airbrush paints are thixotropic, which means that they are quite viscous while not in motion, but become less viscous (having a capacity to flow better) when agitated or stressed - in other words when they are vigorously shaken. In the automotive business, before spraying, paint cans are shaken in a paint can shaking machine for a few minutes, sometimes up to half an hour or more. Many of the better quality airbrush paints are contained in a bottle that also has a ball inside of them to improve the effect of the shaking process. Also empty bottles for airbrush artists to mix their own paints should contain a kind of ball bearing (making them not empty in a literal sense) to make paints less viscous when shaken.

Empty (well, almost) paint bottle with ball

So before you start airbrushing, make sure your paint is thoroughly shaken. Don't hesitate to shake the bottles for a few minutes in a row. If you still can't hear the ball bearing bounce, hit the bottom of the bottle against something that will not break it (...), but cause the ball to be freed from whatever it is trapped in by the shock of the (repeated) collision(s). Holbein Aeroflash paint, for instance, is sold in bottles that contain a ball bearing along with the paint.

If colors are not used for a longer period of time, the ball bearing will be stuck to the bottom caught in the residue of pigments and other particles. During the first few seconds while shaking the bottle only the splashing of the paint can be heard. After some time the ball bearing will be released by the residue that started to dissolve by the shaking and it can be heard bouncing up and down the bottle.

If you don't think the shaking makes a lot of difference, try spraying paint from a bottle that has not been used for a longer period of time. Then shake the bottle vigorously for a couple of minutes and try to spray with what comes out of it then. You will notice a significant improvement in the handling of the paint (much better flow), color intensity and coverage. Not only will the shaking lower the paint's viscosity, but it will also improve the dispersion (even distribution) of the solid particles (pigments etc.) contained within the paint.

Just remember mister James Bond's famous answer, when replying to the bartender's question how he would like his cocktail: 'Shaken, not stirred.'