Airbrushing Polyurethane?

Dave H wrote:
> Has anyone tried putting on the final finish to a project using an
> airbrush as the application tool for either water based or oil based
> polyurethane? If so, any recommendations on brand and model of the
> airbrush?

For what project?

Airbrushes are fantastic for models, small instruments, small toys,
figurines etc... where very thin coats are required so details aren't
obscured. An airbrush sprays an even finer coat than a typical spray
bomb, so more coats are required to build a decent finish thickness,
which isn't usually wanted or required where a typical airbrush is the
best tool. Most airbrushes are also limited to about 2 oz. of finish
per filling, further limiting the project size.

That said, if I'm choosing the airbrush to spray a clear top coat, I'm
also choosing lacquer or shellac, for a fast, dust-free coat and very
thin "shell". All in all, I really don't know how polyurethane varnish
would spray with an airbrush. <G> On the other hand, oil-based
polyurethane is sold every minute in spray bombs, so I don't think it
would be a problem if properly thinned. Water base polyurethane might
be more difficult.

When we're talking top coats, even something as small as a typical
electric guitar body is usually better sprayed with at least a
"touch-up" gun.

Badger 150. Works great.
"Dave H" <[email protected]> wrote in message
news:[email protected]...
>
> Has anyone tried putting on the final finish to a project using an
> airbrush as the application tool for either water based or oil based
> polyurethane? If so, any recommendations on brand and model of the
> airbrush?
> --
>

B A R R Y wrote:

> Dave H wrote:
> > Has anyone tried putting on the final finish to a project using an
> > airbrush as the application tool for either water based or oil based
> > polyurethane? If so, any recommendations on brand and model of the
> > airbrus
> For what project?
>
> Airbrushes are fantastic for models, small instruments, small toys,
> figurines etc... where very thin coats are required so details aren't
> obscured. An airbrush sprays an even finer coat than a typical spray
> bomb, so more coats are required to build a decent finish thickness,
> which isn't usually wanted or required where a typical airbrush is
> the best tool. Most airbrushes are also limited to about 2 oz. of
> finish per filling, further limiting the project size.
>
> That said, if I'm choosing the airbrush to spray a clear top coat,
> I'm also choosing lacquer or shellac, for a fast, dust-free coat and
> very thin "shell". All in all, I really don't know how polyurethane
> varnish would spray with an airbrush. <G> On the other hand,
> oil-based polyurethane is sold every minute in spray bombs, so I
> don't think it would be a problem if properly thinned. Water base
> polyurethane might be more difficult.
>
> When we're talking top coats, even something as small as a typical
> electric guitar body is usually better sprayed with at least a
> "touch-up" gun.

Thank you for you input. My intent was to apply polyurethane as I had
in the past using either a brush or wipe on poly and build up the
finish with 3 or 4 coats. No matter how careful they are applied, the
last coat often contains small bubbles that break as it dries leaving a
less than perfectly smooth finish. What I was hoping to accomplish was
to sand the last coat as I had the others, removing all the
imperfections, and then applying a final thin bubble free coat that
only needs to be think enough to fill in the sanding scratches of 220
or 300 grit sandpaper.

I just don't have the space to set up a large spray booth and air
handler to use a traditional HVLP spray system.

--

"David H" <[email protected]> wrote in message
news:[email protected]...

>
> Thank you for you input. My intent was to apply polyurethane as I had
> in the past using either a brush or wipe on poly and build up the
> finish with 3 or 4 coats. No matter how careful they are applied, the
> last coat often contains small bubbles that break as it dries leaving a
> less than perfectly smooth finish. What I was hoping to accomplish was
> to sand the last coat as I had the others, removing all the
> imperfections, and then applying a final thin bubble free coat that
> only needs to be think enough to fill in the sanding scratches of 220
> or 300 grit sandpaper.
>

Errrrrrr!!! Stop right there. You won't "fill" sanding scratches from 220
or 300 grit paper with a spray application. They will be visible after it
dries. Those are pretty darned coarse grits for a spray finish. If you are
going as far as to cut the previous coats down to flat with 300, then simply
work back up to 1200 or 1500 and finish it off with a rubbing compound. Go
from 300 to 600 to 1000 to 1500. Or better yet, start at 1000. You don't
need anything near as coarse as 300 to flatten a clear coat.


--

-Mike-
[email protected]

Yes!

Standard polyurethane (mineral sprit based) will work with an in-expensive
air brush, provided you get the largest size nozzle and use an air
compressor. You must fuss with the pressure / air flow a bit and practice a
lot to get it just what you want. Be aware: a significant amount of
material will become airborne particulate and slowly settle on EVERYTHING,
including inside your lungs if you don't ware a mask. Don't bother with the
hobby shop 'can-o-air' as not enough air flow for the pressure.

Be aware that many polyurethane makers sell an aerosol can which is much
easier to use, even though there is a bit more overspray. Cost is not too
bad.

Water-based polyurethane has large molecules making up the finish. Thinning
will not break up the long molecules. My Pasche airbrush will not transmit
enough finish to the project; it is mostly the water thinner that get
discharged. To get a high quality water based Lacquer to be sprayed by a
very small air-brush like device, you need one of the products from
http://www.homesteadfinishing.com/

I do very small items and was recommended to use a Walcom STM
http://www.homesteadfinishing.com/htdocs/walcom2.htm
(very bottom of page)
but at that price it is out of my budget for a hobbyist.

Phil


"Dave H" <[email protected]> wrote in message
news:[email protected]...
>
> Has anyone tried putting on the final finish to a project using an
> airbrush as the application tool for either water based or oil based
> polyurethane? If so, any recommendations on brand and model of the
> airbrush?
> --
>