Digital BW, The Print

Mark,

airbrushes come in two main categories: single and double action.
The double action allows 2 movements of the release button: down lets 
progressively more air in, back pulls the needle back and lets more liquid out 
(which is sucked out of the brush by the negative pressure created at the tip 
by the air jet).

I doubt that cheap hobby brushes are the double action sort.

To get an even coat, besides moving evenly and overlapping strokes 
appropriately, you also need to adjust the thickness of the liquid you are 
spraying as well as the pressure. The variables are:
-viscosity
-distance from surface being sprayed
-psi (pressure)
-speed at which you make your pass.

Also: tip if you ever hook up a compressor, be sure to filter out the oil from the 
pump!! You will need both a pressure regulator and one, maybe 2 in-line 
filters. 
The cheap alternative to the compressor is the CO2 tank (needs the regulator 
but not the filter).

Finally remember that it takes twice+ as many coats to get the coverage that a 
brush would give you (see the Golden site for furhter info).

Any other airbrush questions, please ask! I can answer only as memory 
allows - after a decade of the stuff (80's), Apple has come to the rescue in the 
last 12 years or so!

Antonis

(I am responding to your post here because it is not specific to piezo, and 
other BW printers may find this useful. I hope it doesn't inconvenience you.)



>>>

FYI, I went out and bought an inexpensive $26.00 air brush from a hobby
shop with the idea that I would not need an elaborate device since I
only want to varnish prints and thus just need something that will
provide a four to six inch berth. I bought a single action external mix
air brush. It comes with a can of compressed air but also has an adapter
for air brush type compressors. I am not sure this was the way to go but
it was inexpensive and I needed to start to learn somehow. I am still
experimenting and thus far I am a bit disappointed. I can change the
width of the spray but not the volume of varnish being sprayed, that
appears to be a constant. Thus I am getting very fine droplets that dry
in a droplet pattern on the print. Thus I end up with
a sort of a pebbly finish.

So, did I purchase the wrong piece of equipment? Any other ideas or
suggestions on how to improve the output?

Thanks,
Mark<<<

Just a quick note...

For anyone interested, I am fairly certain this is a good way to think about
how your print-head and inks work! Except perhaps you could swap psi for
'head voltage' based on some posts I have read.

Nij

-----Original Message-----
From: antonisphoto@... [mailto:antonisphoto@...]
<snip>
To get an even coat, besides moving evenly and overlapping strokes
appropriately, you also need to adjust the thickness of the liquid you are
spraying as well as the pressure. The variables are:
-viscosity
-distance from surface being sprayed
-psi (pressure)
-speed at which you make your pass.
<snip>