Airbrush Blocking Solved

[Guest]

After returning to modelling about 4 years ago I bought a Harder and Steenbeck airbrush, using model Air paint, but found the nozzle nearly always blocked, sometimes after only 30 seconds. (Yes, I did shake the bottles (all new Model Air) and their ball bearing rattler thoroughly every time I used them.) So I turned to Tamiya TS spray paints which gave a very high gloss coat (essential for vehicles) but are a bit fierce and need restraint.

I recently started the Academy 1/400 Titanic (it’s huge!) which has over 360 separate parts, some very small indeed, on 7 sprues, some big, and it was totally impracticable to consider detaching each one and painting them separately, so I airbrushed them on the sprue using Model Air. This took 5 fills (50 drops each) of the airbrush cup for each of the primer and final coats. During the spraying session of each coat I had to stop spraying to refill the cup (5 times for each colour), and also for about 10 seconds while I swapped a sprue. Each of the two painting session therefore took over 20 minutes to complete. From my earlier experience I would have had to re-clean the AB many many times due to blocking. I also did two other shorter painting sessions.

I had heard of tip drying causing blocking, so every time, either to change sprues or refill the cup, I kept the tip of the AB immersed in about 5 mm deep of Model Air AB thinner, the AB being supported. This prevented tip drying. Also, I discovered Model Air Flow Improver (obviously designed to make paint flow more smoothly through the tip). Result: blocking avoided despite the many times the use of the AB was required to be interrupted.

[Guest]

After returning to modelling about 4 years ago I bought a Harder and Steenbeck airbrush, using model Air paint, but found the nozzle nearly always blocked, sometimes after only 30 seconds. (Yes, I did shake the bottles (all new Model Air) and their ball bearing rattler thoroughly every time I used them.) So I turned to Tamiya TS spray paints which gave a very high gloss coat (essential for vehicles) but are a bit fierce and need restraint.

I recently started the Academy 1/400 Titanic (it’s huge!) which has over 360 separate parts, some very small indeed, on 7 sprues, some big, and it was totally impracticable to consider detaching each one and painting them separately, so I airbrushed them on the sprue using Model Air. This took 5 fills (50 drops each) of the airbrush cup for each of the primer and final coats. During the spraying session of each coat I had to stop spraying to refill the cup (5 times for each colour), and also for about 10 seconds while I swapped a sprue. Each of the two painting session therefore took over 20 minutes to complete. From my earlier experience I would have had to re-clean the AB many many times due to blocking. I also did two other shorter painting sessions.

I had heard of tip drying causing blocking, so every time, either to change sprues or refill the cup, I kept the tip of the AB immersed in about 5 mm deep of Model Air AB thinner, the AB being supported. This prevented tip drying. Also, I discovered Model Air Flow Improver (obviously designed to make paint flow more smoothly through the tip). Result: blocking avoided despite the many times the use of the AB was required to be interrupted.

Hi Steve, I have a HS Evolution and spray Tamiya acrylics and dont experience any issues. I do however clean thoroughly between paint changes and after each session.

[Guest]

Hi Steve, I have a HS Evolution and spray Tamiya acrylics and dont experience any issues. I do however clean thoroughly between paint changes and after each session.

Yes, I used to clean very thoroughly, even also in an ultrasonic cleaner (those things which send ultrasound into a bath of water). I still got blockages, but now I don't need to use the u/sonic cleaner!

[Bugatti Fan]

All these things often come down to experimentation. There are so many variables to contend with when sir brushing, from inconsistencies of the paint viscosity whether sir brush ready or mixed with thinners. Another thing to look at is whether the correct nozzle is being used on the air brush. I have used Badgers for years. The first one had a fine nozzle on it and blocked occassionally, but I bought the next size up nozzle and found it worked better for me if the paint mix was a bit thicker. Of course all these things are subjective. You tend to get used to a particular product(s) but sometimes get problems when a change of paint type comes about. When I finish and clear up, to clean my air brushes I firstly spay through neat thinners comparable with the paint I have been using. I follow on with neat cellulose thinners, and finally with Vallejo dedicated air brush cleaner checking it sprays through clear. This works for me as I very rarely have to strip an air brush completely for cleaning.

[Tim Marlow]

I rarely get blocking on my Iwatta, but I do strip and clean down at the end of every session. Takes no more than a few minutes as I have a quick release needle arrangement. Another tip is to always start the air before the paint, and stop the paint before the air. In effect, the air is on all the time unless I put the brush down. That’s helps to clear paint out of the brush body and needle while it is still fluid and not dried on.
Cheers
Tim

[Bugatti Fan]

Tim, I have never tried an Iwata but understand that they have a great reputation having come onto the market some time after the Aerograph, Badger and Paasche brands were already well established. Had a go with a Harder and Steenbeck on Little Tools stand at a model show and was impressed with the quality of the instrument.