Need troubleshooting help!

The first thing I'd suggest is to get down to basics.

• Make sure tha paint nozzle is open sufficiently. I know this sounds silly, but there have been cases where newcomers to airbrushing didn't know they had to open the nozzle to allow paint to flow.
• Check for air leaks between your regulator and your airbrush. Your reg may be set to 25psi but if your hose is leaking, it's not delivering it all to your AB.
• Try spraying some clean water through your brush. If it sprays water but not paint, that would suggest that your paint is too thick.

I know this sounds dumb, but you are turning the cone about 3 -4 turns open from the fully closed/tight postion correct ?

are you using the cup or the bottle attachment ?

if it is the bottle attachment, there is a tiny hole in the cap, and that hole needs to also go through to the inside gasket. if it is blocked, it cant siphon.

use water to test the AB , spray it on carboard box or something.

The Paasche H is a real classic and my first AB dated back to the 80's. It requires a bit higher pressure than most internal mix, gravity feed airbrush today. Paasche "Recommended Air Pressure .5 to 1 CFM @ 20 to 45 lbs (psi). depending on tip size and fluid being sprayed". You can find the manual online at the Paasche site.

http://www.paascheairbrush.com/2008pdf/H%20&%20HS%20Airbrush%20Parts%20List.pdf

OPERATING INSTRUCTIONS: Approximate Working Pressures:

• 20 lbs. or Less: Stipple and granulated effects, pressure will vary with viscosity of fluid.
• 20 to 30 lbs.: Medium consistency water colors, inks & dyes.
• 30 lbs. or More: Heavy fluids, acrylics, reduced lacquers, varnishes, paints or ceramic glaze.

Your shop compressor should have plenty of pressure and flow rate to drive the airbrush. Yes, 25 psi is too low for enamel using the H. The shop compressor's regulator usually don't work well at the low end of pressure. You may consider buying an airbrush type diaphram regulator/filter unit and connect it through a long airhose to your workbench. (You can find quite a few for under $20 with free shipping on Ebay.) Set the shop compressor to 60 psi and use the AB regulator at the workbench to control the pressure you need.

You may have dried paint inside the airbrush when you used it at such low pressure. Take the whole front end apart, soak them in paint thinner overnight and reassemble it. Try 35 psi with water first. Adjust the nozzle for flow pattern you like before loading thinned enamel. I use most acrylic myself. There are many discussion on thinning ratio of enamel on this forum before.

Good luck and happy airbrushing.

You guys have given me some good ideas.

On the first try, the H1 tip would barely spray thinned-out Testors enamel.  When I cleaned the brush, paint thinner sprayed through easily.  But after changing to the H3 tip, not even thinner would move through it.  Also checked to make sure I don't have tips, needles, and nozzles mixed up - they all have the correct number of hash-marks on them.

If air is coming out the nozzle, then it certainly has to be either not enough PSI to suction up paint, or something blocking the tube.  I'm using the bottle attachment for now.  The little vent hole on the lid is clear, and the feed tube and attachments appear to be clean.

I will check the connections again and try 40 PSI.  Thanks all for help with a very frustrating problem.

I do respect the experience here, but just wanted to chime in again, and say that I routinly use 20-25psi (indicated) with my H. so it can be done.

so, what happens when you turn/open the cone up ? if you turn it open a lot, something should happen! will this thing spray Water ?

Another things comes to mind....if you used teflon tape to seal air connections...maybe a sliver of it has worked into the AB airways, and though you get air, it is partially blocked.

Finally got water, thinner, and paint to go through the other night.  I didn't have the collar end of the needle assembly seated all the way up against the mount (the little ball-shaped thingy).  Bringing the needle end further up into the nozzle seemed to help. 

Using the no. 3 needle assembly, water and thinner went through just fine.  However, Testors gloss white splattered like crazy (yes, I blew out all the water first).  It was diluted with just a drop or two of thinner.

So, how thin does the paint have to be?  What's considered "best practice" here?  50/50 paint/thinner or just unthinned paint with a no.5 needle? 

Thanks again all...

Pat C wrote:

So, how thin does the paint have to be?  What's considered "best practice" here?  50/50 paint/thinner or just unthinned paint with a no.5 needle?

As a rule of thumb, thin your paint to the consistency of 2% milk.  For additional discussion beyond the referenced thread, use the search feature as this is a topic that has been discussed numerous times, probably for the simple reason that improper thinning is one of the biggest problems you'll have with an airbrush.

From what I can gather, I would guess that you need additional thinning.  Although there are no hard-and-fast rules about how much thinner to add to paint, mostly because there is so much bottle to bottle variation, adding a drop or two seems likely to be way too little.  On average, I probably add thinner at a 1:2 or 1:1 ratio of thinner to paint.  If you underthin your paint and force it out through a combination high airpressure and a wide open nozzle, you won't get nearly as nice a finish as you could otherwise.  It will likely be be thick, lumpy, and have a lot of overspray.   

Just to give you a reference point of operation, I also have a Paasche H and using the No.1 tip, I typically spray with an air pressure of between 15-20 PSI.  Depending on whether I'm doing detail work (camouflage) or an overall coat, I paint anywhere from half-an-inch to 3-4 inches from the model.  I've never really counted the number of turns that I open up the nozzle with, but when I'm painting (as opposed to cleaning), I never open the nozzle so far that it extends beyond the tip, i.e. the end of the tip is always projecting out a bit from the nozzle opening.

It probably seems a bit overwhelming, getting the right combination of paint thinning, nozzle opening, air pressure, painting distance.  We've all been there, but with experimentation, practice and experience, you'll find it gets a lot easier.

Andy