RE: Airbrushing, masking, and Frisket

> 1) Someone please explain to me why I'd want (and what is) a double
action
> airbrush over a so called single action one? 

explained by others a good double action can go 1/8 inch or less but
you need to control the air pressure which leads to: 

> look for in an airbrush/compressor? I want to buy a good one. 

two general types, direct piston, or diaphragm to tank. 
The best are diaphragm to tank as you don't get the pulsing of
the piston, but they are double the price of piston. I have a piston
to a regulator and moisture trap and that seems to be enough to
eliminate pulsing of the air flow. If money no object get a diaphragm
compressor with tank, moisture trap and regulator. 

The regulator is critical to fine line work as even with a double 
action brush it allows you to set the pressure low enough to get
minimal flow - viscosity is also a factor as the paint has to be thin
to get a fine line, see below.

> 
> 2) Frisket - where would I find these sheets? Art supply? Drafting?
Some
> other place?

Art Graphics shops and where they sell air brushes.

> 4) Airbrush paints - Must I buy a whole new set of paints? I have
Tamiya and
> Humbrol and Ral Partha paints galore... must these be added to with
another
> whole set for an airbrush? Or is thinning and using them an option? If
so,
> how much to thin, or with what? 

Humbrol enamels? Enamels need a specially designed air brush to
work well as the pigment is coarse and some air brushes are 
designed for graphic work and son don't take to the coarse pigment.

There are several air brush models designed for enamels, strangely the
one I have is made by Humbrol. 

Thinner for enamels, I use humbrol thinners/cleaner.

thinner for acrylics, water, add a bit of vodka to lower the 
surface tension, I dont like putting detergent in my paints.

Thinning is a heuristic process, and it depends on the air brush,
air pressure and paint you are using. 

Thin, test spray, adjust. There is also a thing called a viscosity
cup which measures paint viscosity by surface tension. The milk tip
is ok but its very hard to judge, basically it needs to be quite thin
50 - 60% thinner as stated.

Thats why I bought the air brush paints by badger as they seem to have 
formulated them to work under various conditions of air pressure and 
to flow well. I was getting about 1/4 inch lines with a cheap set up. 

--
Tim