Strange Airbrush Problem ...

[Garth]

Ok, maybe someone can help me with this ...

 

I have a Badger 150 (double-action). In attempting to paint my latest (EA-6B) it's developed this pattern of "pulsing"/"surging". What will happen is that I'll get a nice flow of paint for a second or two ... but it will then taper off to nothing. After a second or two of just air there will be a "surge" of paint through the nozzle.

 

Couple other factors ... I have both a Badger compressor (300, iirc) and a H/C with a 13 gallon tank. The proble occurs with both. Both have air regulators ... I've tried varying both the pressure (from 15 to 25 psi) and the thinning ratio of the paint.

 

The problem also occurs regardless of whether I'm drawing paint from a bottle through a cap attachment, or using a color cup. As best I can tell the airbrush itself is clean as a whistle and all parts (including the little teflon ring around the needle that sits right behind where the paint flows through the brush) are present and working.

 

One thing that I've been able to trial-and-error out is that the problem is reduced, somewhat, if I use a Fine needle with a Medium tip. With a F/F or M/M arrangement the problem is much more pronounced.

 

Lastly ... the problem only appears to happen when I am spraying paint. Doesn't occur when I spray Future, ammonia (to clear the Future out of the brush) or water (to clear the paint ... I'm using acryls). However, I've thinned the paints all the way down to an 80/20 or so thinner/paint mix and it still happens ...

 

Any ideas?

 

--Garth

[Garth]

Oh, one more thing. I have two inline moisture traps. One is a metal Paache, the other a plastic Badger. Both have drains for emptying out condensation (and are free of such), both are located within a couple inches of the brush's airhose connection. Problem occurs with both.

 

--Garth

[Brad Sallows]

The only time I've experienced that sort of problem is with "lumpy" paint. That can happen irrespective of paint / thinner mix. (I've never had the problem with stuff out of the original jar; my lesson learned is that once I prepare and use a particular mix in another jar, I don't reuse any leftover contents days or weeks down the road.)

 

Have you a second air hose to test to further isolate where the problem "can't be"?

[Garth]

Originally posted by Brad Sallows:

Have you a second air hose to test to further isolate where the problem "can't be"?

 

 

Yup ... I have two separate hoses, each with its own inline trap. The only thing that I haven't tried is switching the traps between hoses, but I'm not sure if that's even worth the effort.

 

--Garth

[Brad Sallows]

Since you've had some impact by switching needles, it does seem like it might be something between the air intake on the needle and the tip. Have you enough parts to swap various components of the airbrush (ie. the tip assembly, for example)?

[EW]

Originally posted by Garth:

if I use a Fine needle with a Medium tip.  With a F/F or M/M arrangement the problem is much more pronounced.

 

Lastly ... the problem only appears to happen when I am spraying paint. 

 

The above, in bold, strongly indicates that the thinning ratio is the main problem. With a fine needle on a medium tip there's more space for the paint to pass trough, even if it's too grainy. This problem of yours happens to me from time to time (only with PS) and everytime I have messed up on the thinning ratio. IOW it goes away if I add some more water. BTW what brands/types are we talking about in this case?

 

Have you tried to warm the paint in hot water, prior to airbrushing it? It sure makes it flow more easily.

 

Furthermore, I would suggest, that you take the entire airbrush apart and clean it. I do that between each painting seesion to avoid biuld ups. The PS range and some of the Aeromaster are a real PITA, when it comes to that.

 

Gotta rush, p*ssed of like hell, since I've managed to lose a part to my nearly completed Bf-109. Sod this hobby Hope it helps. I'll check back tomorrow.

 

EW

[Garth]

Brad, EW,

 

I'm inclined at this point to agree that it's with the thinning. Or, more specifically, with the acrylic paint (I'm using PollyScale, btw), which I'd thinned all the way down to 80% water (or, rather, acryl thinner) with no effect. I had to spray some white earlier this past evening, and my "magic white" mix (capable of covering BLACK with one coat and no runs) enamel mix did just fine.

 

As it is, I'm going to end up trying out a different needle/tip combination. In the course of spraying I set the airbrush down on my garage workbench incorrectly and it nose-dived right down onto the concrete floor. Bent the needle over to a 90 degree angle and shattered the nozzle tip. Just more money to support my local hobby shop, right (and jeeze, they're going to LOVE me if I have to start switching over to enamels ... )?

 

--Garth

[Garth]

You know, that's a really excellent point as well. In our new house, my spraying area has been relegated to the garage. Which isn't heated. Temp was probably in the low-mid 40s (f) today.

 

I'm not sure that pre-warming would help, as the temperature would drop back down pretty quickly. I'd need something that would allow me to keep the paint heated throughout the process. I have a Mr.Coffee mug warmer (cost me all of US$8 a year ago) that I use to heat my decal water bowl. Might have to go buy another.

 

--Garth

 

Originally posted by Ensign wanker:

Have you tried to warm the paint in hot water, prior to airbrushing it? It sure makes it flow more easily.

[EW]

Garth,

 

AFAIK 40 degrees Farhenheit equals 4.44 degress Celsius and that's close to the freezing point. So maybe you can find an argument to get indoors, like promising to build a spray booth?

 

As for the PS acryclics, I always thin them with 21-22% of distilled water. Using distilled instead of ordinary water from the tap, makes a difference. When using PS I also never fill the cup more than 50%, since the pigments have tendency to sink to the bottom. Adding the water/thinner first, followed by the paint, is also a good practice.

 

Finally if you have experimented with a thinning ratio up to 80% and not reached a solution, I suspect that you somehow might have damaged the needle/nozzle. As you know, even the smallest misalignment/damage, that barely are visible for the naked eye, have a great impact on the end result.

 

Hope it helps and keep us posted.

 

EW

[Jacques]

actually, having an extensive background working with PS paints as well, I think the problem is temp. I have found that if a fair number of PS paints go below freezing, the pigments tend to seperate out from the carrier and when the whole mix is raised to a higher temp, the pigments tend to clump. It makes the paint look grainy, and nothing seems to reintegrate the pigment to the carrier. I tend to buy my paint in person from hobbyshops in the winter as I do not like the mail to deliver messed up paint from online stores.

 

I think the main problem is using the PS paints in such a cold environment. You need to move that operation in doors, to the warmth...or else heat that garage!

[Garth]

Well, I made an error of omission in my earlier comments ... all the hardware for spraying (airbooth, compressors, airbrushes, etc) is located in the garage, but the actual paint is stored in the house and not moved to the garage until I'm ready to spray.

 

Moving my spraying area indoors isn't an option ... there's no other area of the house that has the garage's unique combination of available space, ventilation and ability (or rather, williness on my part) to sustain spraying-related damage (as it is, I move the car located closest to the booth out into the driveway while spraying). I've thought about buying a space heater (about $50) for temporary heating, but it's not something I'd run all the time and by the time it actually warmed the garage up I'd be done with spraying (however, I HAVE noticed that my Jeep -which has a tendency to overheat- does a pretty good job of heating the garage after having been driven 10-15 miles).

 

I've also thought about moving the spraybooth up into the attic, which is a bit warmer since heat rises. Downsides to this are that the opening isn't big enough for me to get my workbench through (I'd have to build another one up there), spraying in the summer would be absolute misery and the fact that there's a good bit of loose sprayed insulation would probably result in my models having a good deal of cr*p embedded into their finishes.

 

I'm getting ready to dive into my next model (Hasegawa F-102A), and it looks like I either have the right paints (black, dark gull gray for the cockpit) in enamel already, or don't have them on hand (ADC Gray) and can buy them in enamel from the get go ... so I should be in good shape.

 

Thanks again guys!

 

--Garth

 

Originally posted by Jacques:

I think the main problem is using the PS paints in such a cold environment.  You need to move that operation in doors, to the warmth...or else heat that garage!   

[Jacques]

Ok Garth, I hear you.

 

1. Before you abandon the house, you may be able to "creatively" add a spraybooth without it being a huge problem. I have seen systems hooked up to the clothesdryer vent and hung on a wall over a dryer or freezer...just an idea, rather than abandoning all hope.

 

2. If you stay in the garage, using something to help heat the immediate area that your airbrush will occupy is not a terrible bad idea. Also, immersing the paintjar in hot water and using some kind of thermal wrap on the jar/botle/cup is not a bad idea either. Thermal tape for piping may be something that will work as well if wrapped around a jar.

 

Mix the paint in the house..ie, have the paint in a colder area for as little time as possible. Even if set down for a few minutes, a glass or metal container looses a lot of heat (metal and glass have very high heat conduction values, or low R values). Also, Acrylics are more sensative to heat, although enamels will start to have a poorer finish and have some adhesive issues as you spray them in colder temps. Cold temps are just going to be a pain for atomized paint particles.

 

3. Another suggestion I was given was to save up all that airbrushing you may need to do for that 1 really nice day that comes along, and just build kits as far as you can until then. Or prepaint kits on the sprue in large numbers and then build them when it is too cold to airbrush.

 

4. as for Polly S acrylics, yes, they can tend to "lump up". Even if you buy paint from a hobby shop and take to a nice clean home, who knows where that bottle has been? It could have been in a unheated warehouse, a unheated cargo truck, or sitting outside a door in a box in the snow for hours. Best bet is to strain that paint...I do it thorugh my wife's old pantyhose. Cut a piece of pantyhose bigger than the size of the opening on the bottle to be transfered to, and pour the paint through. If it does not seem to flow properly, even if thinned, you may just have a problem bottle of paint and need to get a new one.

 

Hope this helps give you some ideas and solve the problem.

[EW]

BTT

 

I think this topic could be useful for future reference/guideline, since it gives some sound advice on handling airbrushes and thinning paints etc.

 

EW