Please help with frustrating airbrush problem

GRANT ED wrote:

As for the bubbles. I took the airbrush as far apart as it would go and spent almost an hour cleaning to make 100% sure dried paint is not causing my problem. I still have bubbles. When I took my brush apart from cleaning I noticed some paint leaking past the gold part in my pic. Both surfaces of this part are clean and I can only assume the air leak is here. Does the end cap push this part into the airbrush to seal it? I did consider putting a paper gasket under the tip to push it out further which would allow the end cap to push the tip holder back into the airbrush a bit firmer to help with sealing. Does this sound like a good idea?

Do not attempt to put any sort of additional packing in. Your airbrush is build to incredibly fine tolerances and will only cause more problems.

Your user manual provides a troubleshooting section for bubbling. Follow those steps and see if it helps. Ensure that you withdraw or partially withdraw the needle before removing or replacing the tip. (and remember to re-seat the needle after the tip and head has been reassembled.

The only other thing I can think of whch isn't covered there is that your needle may be bent and may be causing a slight offset. You can check this by withdrawing the needle completely and rolling it on a perfectly flat surface (such as a piece of glass) - if it is bent, you will need to replace the needle.

Dr. Coffee wrote:

MikeV wrote:  Dr. Coffee wrote:  MikeV wrote: The bubbles in your paint cup indicates there is a leak. Sorry but that is incorrect. The main reason for bubbles in your paint cup is an obstruction in the nozzle such as dried paint that causes air to be forced back into the paint cup. What do you mean? Paint outside the paint nozzle 'catches' air coming from the air channel and redirects it back in the paint channel? Sorry, sounds a bit far-fetched... DoC No. Paint dries in the tip and causes a hinderance in the airflow which is directed back into the cup. These are internal mix airbrushes. Do you own one? Ah. No, I don't own one. Haven't seen one, either. With the one I've been using the paint meets the air literally at the tip of the needle. Thanks for the enlightenment. DoC

I see. Yes you have an external mix airbrush or spray gun whichever it is.

MikeV wrote:

Dr. Coffee wrote:  MikeV wrote: The bubbles in your paint cup indicates there is a leak. Sorry but that is incorrect. The main reason for bubbles in your paint cup is an obstruction in the nozzle such as dried paint that causes air to be forced back into the paint cup. What do you mean? Paint outside the paint nozzle 'catches' air coming from the air channel and redirects it back in the paint channel? Sorry, sounds a bit far-fetched... DoC No. Paint dries in the tip and causes a hinderance in the airflow which is directed back into the cup. These are internal mix airbrushes. Do you own one?

Ah. No, I don't own one. Haven't seen one, either. With the one I've been using the paint meets the air literally at the tip of the needle.

Thanks for the enlightenment.

DoC  

Today I went out and bought a water trap. I then tried airbrushing as per normal and I still had the same problem. I then kept adding thinner and trying again. This worked as at some point the splatter problem went away. I did find though that I do have to have a lot of thinner to get rid of the splatter. I would estimate I need a mix of approx 5 parts thinner to 1 part paint. Does this sound excessive? Do I still have a problem that I am covering up by having very thin paint? I did find I needed to do a lot of coats to get coverage as the paint is very thin now. Once again I tried changing the pressure but it did not seem to make a difference.

As for the bubbles. I took the airbrush as far apart as it would go and spent almost an hour cleaning to make 100% sure dried paint is not causing my problem. I still have bubbles. When I took my brush apart from cleaning I noticed some paint leaking past the gold part in my pic. Both surfaces of this part are clean and I can only assume the air leak is here. Does the end cap push this part into the airbrush to seal it? I did consider putting a paper gasket under the tip to push it out further which would allow the end cap to push the tip holder back into the airbrush a bit firmer to help with sealing. Does this sound like a good idea?

Dr. Coffee wrote:

MikeV wrote: The bubbles in your paint cup indicates there is a leak. Sorry but that is incorrect. The main reason for bubbles in your paint cup is an obstruction in the nozzle such as dried paint that causes air to be forced back into the paint cup. What do you mean? Paint outside the paint nozzle 'catches' air coming from the air channel and redirects it back in the paint channel? Sorry, sounds a bit far-fetched... DoC

No. Paint dries in the tip and causes a hinderance in the airflow which is directed back into the cup. These are internal mix airbrushes. Do you own one? Put water in the color cup and put a rag over the nozzle of the airbrush and push down and pull back on the trigger. You will see bubbling in the color cup because the airflow is being forced back into the cup under pressure because of the negative pressure at the tip. This is what happens when acrylics especially start to dry and build up in the tip. Far fetched? I have been airbrushing a long time my friend and no it is not far fetched.

I have been doing some more reasearching on various airbrushing websites and the two problems that were mentioned over and over for bubbles in the cup was an obstruction in the tip and/or an air leak in the tip area. I am sure I don't have a blockage as I must have the most cleaned airbrush in the world at this point. I cannot see anywhere that may be leaking. As best I can tell all the seals and gaskets are in place and look ok. The tip and needle also look fine. A bit later today I am going to get a water trap. I'll also do some testing with some paint thinned to different amount and I'll post my results so you guys can see if you notice anything.

MikeV wrote:

The bubbles in your paint cup indicates there is a leak. Sorry but that is incorrect. The main reason for bubbles in your paint cup is an obstruction in the nozzle such as dried paint that causes air to be forced back into the paint cup.

What do you mean? Paint outside the paint nozzle 'catches' air coming from the air channel and redirects it back in the paint channel?

Sorry, sounds a bit far-fetched...

DoC

The bubbles in your paint cup indicates there is a leak.

Sorry but that is incorrect. The main reason for bubbles in your paint cup is an obstruction in the nozzle such as dried paint that causes air to be forced back into the paint cup. When you backflush an airbrush to clean it you will see bubbles in the cup as well for this very reason. Tip dry is the normal culprit. Keep the tip and needle clean and if you are going to let the airbrush sit for more than say 10 minutes then empty the cup, spray some thinner through it and then put paint back in the cup when you are ready to paint again.

GRANT ED wrote:

Are you talking about a gasket between these two parts? If so there isn't one, should there be one?

Of the parts you have pictured, the tip (the larger of the two parts) is a friction fit into the body of the airbrush.

If this isn't seated cleanly and firmly, it's a possible source of an air leak back into the paint path. 

Any amount of dried paint on the mating surfaces of this part and the recess in the body which it goes into will cause a bad seal and may leak air into the paint path (and back into the cup. If the air cap (which fits over this part) isn't tightly screwed down (but not too tightly) it may also allow the tip to leak.

Make sure the tip/nozzle and air cap are fully assembled before inserting and locking the needle into place.

Again, I don't know the model you use so I don't know the details of what should be there and what should not. I would expect to find a gasket at the rear end of the nozzle. If all goes to plan, this link shows some images of replacement items for my kit:

http://germanairbrush.com/accessories_harder.html

There are some needles at the top of that list, but items 10'ish from the top are nozzles. The white material on the left-hand side in the pictures are teflon gaskets that seal the paint flow internal to the nozzle, from the air flow around the nozzle.

If that gasket doesn't seal perfectly, the pressurized air that comes from the compressor is pushed into the paint channel and can escape out through the paint cup.

If your airbrush has O-rings for seals, they serve the same purpose - preventing air to escape into the paint channel - so that's where you should look for the cause for the bubbles.

DoC

Are you talking about a gasket between these two parts? If so there isn't one, should there be one?

The only other gaskets I can find are a few o-rings.

I have had a close look at the parts and can't see any damage. I also am very particular about cleaning so I don't think that is the problem. As for the water trap. As best I can tell I don't have one and I do leave the tank pressurised all the time. If this is a big problem I will get a trap and try the other things you have suggested. Thanks for the help.

The bubbles in your paint cup indicates there is a leak. I don't know the airbrush in question, but assume it is a double-action brush. If so:

1. Dismantle the nozzle + nozzle holder from the airbrush body. There should be a gasket in there somewhere, between the nozzle and paint cup.
2. Clean the gasket. Soak it in paint thinner or airbrush cleaning fluid and gently remove any paint residue.
3. Inspect for flaws or damages. I once had the same problem, when it turned out that there was an ejector mark in the gasket, left from the production. 
4. Clean the both the nozzle, nozzle holder and airbrush body for paint residue etc while you're at it. This is one of those cases where cleanliness makes or brakes the deal.

As for spatter, try to dilute the paint far more - 1 part paint to 5 or 10 parts thinner. Or reduce the pressure as far as you can. Remove moist from your air system if you are using a compressor. Make sure the moist trap is empty. I always release the pressure through the moist trap after I finish a paint session. That way the moist trap never fills up, and the system is never left pressurized.

Apart from that, make sure that the needle and internals of the airbrush are clean, and that no paint residue is left inside to disrupt the airflow.

DoC