Blowback bubbling in paint cup

[Andrew McLean]

Hi all,
My (10 year old) Iwata HP-B Plus airbrush has just started to blow back bubbles into the paint cup.
I have checked all possible causes (that it is possible to see from the outside)
- thorough clean of whole airbrush
- tight nozzle
- no discernable damage to nozzle or needle

Another cause maybe a leak or damage inside the airbrush with the air flow channel. Unable to get inside to this area to check.

Any other causes you experts can think of that may cause this problem?

Three options
1. Purchase new nozzle (as this is quite worn from 10 years use but as I said no discernable damage) and find out if that is the actual cause.
2. Send whole thing to Japan for the Iwata technicians to check out, if they do that?
3. Purchase new airbrush

Any help greatly appreciated.
Cheers
Red Dog

 

[JackEb]

your most likely problem is old paint in the nozzle.
depending on what paint you used you'll need the appropriate thinner.
for createx (and probably most acrylic/water based paints) I highly recommend the Createx restorer. that stuff takes the varnish off of my hairy artist brushes !!
find a small pot (with lid) and soak the nozzle and air cap in there for a day or two. use either the needle (GENTLY) to push the junk out, or a whittled down toothpick or a piece of fishing line also works well if its the right size.
some diluted dish liquid around the head will show any leaks quickly when you press the trigger.
don't over tighten the nozzle ! you don't need that breaking off in the body - although its fixable it can be problematic.
chap stick is a quick and easy thread sealer, just don't go to heavy handed with it, a little dab will do.

a new nozzle will be an easy solution, no need for a whole new brush or sending it off to a tech.

 

[JackEb]

this thread should also be of help

How to clean Your Airbrush

Here are some Videos on cleaning Your brush taken from the Iwata site, but the principals are the same no matter the brush. Also, down the right hand side on the Iwata site, they have a whole list of helpful topics under the "Lets get started" header. Quick Color Change End of Spray Session...

airbrushforum.org

 

[erwin de pan]

See if your nozzle goes past the air cab. is it properly tightened?
See if the air cab still has a nice round hole.
Is the nozzle still in the middle of the air cab?
There can't be much wrong internally.
if you haven't dropped it or if the nozzle is screwed in crookedly.

 

[Andrew McLean]

Thanks JackEb. I assure you the nozzle is clean as is the rest of the airbrush. Gave it a thorough clean after finding the bubbling happen.
Thanks also erwin de pan. The needle goes past the first nozzle (part No.2 in the parts list) but not the second (part No.1). Needle still in middle of the air cap.
Thanks for your time and answers.
This has really got me stuck. Unable to see any damage to the needle or nozzle under magnification hence my thoughts of something else internally.
A$100 for new nozzle or A$265 new airbrush?
Cheers
Red Dog

 

[DaveG]

There really is not much that can cause the issue you are experiencing, and they all focus around the nozzle. The air channel through the brush is not subject to any sort of damage or failure. Even if damage could occur with the air passage, it would lead to air escaping the brush before encountering the paint path. There are two things that are most probable - the first being that the nozzle was removed for cleaning, and air is not bypassing the nozzle base past the threads and entering the paint path behind the nozzle. Beeswax or Chapstick applied to the nozzle threads before screwing it back in will most likely solve this issue. The other is that the nozzle has actually sustained a crack. The crack normally run from the leading edge, running back towards the base. They can often be almost impossible to see unless you are spraying color, then look at the nozzle before cleaning it will often make the crack visible along the side of the nozzle. It can also usually be seen in the spray pattern. If the pattern is no longer round, but more "D" shaped or oval it can be an indicator of a damaged nozzle. If this is the case, there really is no alternative but to replace.

 

[erwin de pan]

Try Dave G's suggestion first
Just looked at the prices at my local shop.And a nozzle + nozzlecab and a needle is 120 euros. 0.2 or 0.3

Don't know if theCreos/mrHobby parts also fit on an HP, but they are half the price.

 

[DaveG]

Try Dave G's suggestion first
Just looked at the prices at my local shop.And a nozzle + nozzlecab and a needle is 120 euros. 0.2 or 0.3

Don't know if theCreos/mrHobby parts also fit on an HP, but they are half the price.

The Creos/GSI parts will fit a "Plus" series, but not the older HP series.

 

[Andrew McLean]

Thanks DaveG, a crack in the nozzle so fine to not been seen is most likely.
I will give the bees wax/chapstick method a go that both you and Jack Eb have both recommended and see if that changes anything.
Appreciate your help and recommendations guys.
Cheers.

 

[Andrew McLean]

I will also look into the Creos/GSI parts as a viable solution.

 

[DaveG]

I will also look into the Creos/GSI parts as a viable solution.

The nozzle from the PS270 should work - stick with an Iwata needle, though. The Creos needle is larger diameter.

 

[Andrew McLean]

Tried spraying with some chap stick on the nozzle thread and unfortunately no change. Must be a fine crack in the nozzle.
Looking at the Creos/GSI parts, thanks for the previous tip DaveG.