fine line spray clogging......

When I've had to do fine line work with model paints, I almost constantly have to tweak my thinner ratio. When the paint started acting like you describe, I'd add a drop or two of thinner, if it wasn't covering as well as it needed to, I'd add a drop or two of paint. Try mixing just a hair more thinner into your color cup and see how that works. Experiment some and remember that you can always add a drop or two of either paint or thinner.

are you using a filter to strain the paint?

Had the same problem when I started airbrushing. Over the years I've developed this check-list for fineline spraying:

Use only fresh (new) paint
Shake the bottle of paint for 1 min with a couple of copper BB's in-bottle
Stir the paint in-bottle for 1 min.
Fine line spray mix: 1 part paint to 1 part thinner
General spraying mix: 2 parts paint to 1 part thinner
Strain mixed paint with plumbers mesh or panty hose
Pour strained paint into airbrush
Regulate compressor to 10 psi for fine line spray
Regulate compressor to 15-20 psi for general spraying
Tests spraying characteristics on a srap sheet of styrene plastic or an old model
Once I'm satisfied that the spray pattern, coverage, consistancy are acceptable.....I move to the model and begin spraying.

* Note:
Be mindfull that with acrylics, it is a fact of life that they dry and clog the airbrsuh tip more frequently than with enamels. While using acrylics, keep a thinner moistened q-tip nearby to frequently wipe the airbrush tip to minimize clogs. Also make certain that the airbrush is thotoughly clean prior to and after your airbrushing sessions. Hope this helps!

ok. thanks for the replies.... will follow the recomendations to see how it works out.