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Thursday, 1 August 2013

Quick Tips: Overcoming Airbrush frustrations

As a final update to this post (Now autumn 2014) I've added a section right at the end - possibly the most important section of all.

I originally wrote this post in the summer of 2013 when I was working hard to get into airbrushing for the first time. Since then (it's now Autumn 2013) I've found and overcome more problems so I thought I'd share them alongside my original findings.

All the newer updates are in cyan text, all the original stuff is in white.

I'll start by saying that I'm no expert on this subject. Not by a long chalk.

I've owned an airbrush for a couple of years now, but the amount of time I've actually logged using it doesn't amount to more than a few hours, and at least 75% of that time I would classify as "getting frustrated" time.

What you need your airbrush to do is the one and only job it was built for - shoot paint evenly. Actually getting the airbrush to do this has been my biggest frustration as an airbrush owner. I've spent far more time failing, getting stressed and wound-up by the airbrush than I have actually achieving results with it so far.

But, that said I have managed to overcome some of those frustrations recently and am starting to get more of a feel for the airbrush. My top tips at the moment are as follows:

  1. Mix your paint thoroughly. I bought a milk-frother to help out - it's brilliant and very inexpensive (less than £2.00) and will blend your paint with your thinning medium with very little effort, An image is below for reference.
  2. Mix your paint with the correct "medium". What is "correct" for you amounts to "whatever you can use safely and happily". There's a lot on the web about using "Windex" (an ammonia-based cleaning product, not available in the UK due to marketing restrictions on ammonia) and Iso-Propyl Alcohol (IPA) to thin acrylic paint on the web. I'm not going to say that that advice isn't valid, but tapwater seems to work just as well. I saw a video of a seminar by the VP of Badger airbrushes on the website a while back - he advocated just using water too. Update: Since originally writing this article I've changed my stance on this somewhat. I'm now using a 50/50 blend of tapwater and IPA. The reason being is that I found just using water that the paint was taking a long time to dry on the model. As the IPA is an alcohol, it evaporates much faster so you can handle your model a bit more easily.
  3. Take care to remove any particles from the paint. They *will* gum up your brush. I bought a tea-strainer to help me with this. After you've mixed your paint with your chosen medium, run it through the strainer. I've never yet done this without catching some particles. An image is below for reference.
  4. Aim for that "milk-like" consistency that everyone talks about. This seems to cause much confusion, but what I try to do is to get my paint to behave the way milk does by visualising the way milk runs down the inside of a glass or bottle if you tip it at an angle then level it out again - it leaves a thin film that thins further as it runs down into the glass. Try to get your paint to do that.
  5. I tend to use a gravity-fed brush and this item of advice pertains particularly to that brush type: don't overfill the cup. I'll explain why in the "How to clean" and "When to clean" sections, below. I never fill mine more than about 40% full.
  6. If in doubt, clean it! Even with all these precautions the airbrush still needs periodic cleaning, often in mid-job.

The tea-strainer (upper) and milk-frother (lower). I'm sure you'd worked it out anyway.

How to clean (Refer to the schematic below for names of some of the parts):

  1. Regularly remove the nozzle-cap and give the protruding needle-tip a wipe with a soft tissue. As a test, if you retract but don't depress the trigger ("main lever" in the schematic below) you should see the needle pull back out of sight. If you wipe the airbrush tip on your tissue it should leave a thin line of paint. If not, you have a blockage.
  2. With the nozzle-cap removed, look into the front of the nozzle-cap. Paint builds up here and may cause the aperture that the needle protrudes through to become blocked. Clean it out with a q-tip or similar.
  3. "Bubble" your brush. Take care with this if you have a lot of paint in the cup as it will overflow. Cover the nozzle-cap with your finger and depress and pull-back on the trigger. This will cause a backflow of air from the tip of the brush along the needle and back into the cup. If there are any particulates blocking the flow of paint they should be blown back into the cup. This is one of the reasons I advocate not overfilling your cup.
  4. Rinse it out - tip any paint you still have in the cup back into your paint bottle, turn off your compressor and disconnect the air-hose. Walk to your sink and slowly run cold water into the cup to wash out all the remains of the paint. This is particularly effective when you've emptied the cup by "painting it dry" and then "bubbled" the brush straight afterwards. Leave a small amount of water in the cup and when you've reconnected everything, shoot the water through the brush onto a tissue or neutral surface. You should be able to see a neat cloud of paint with no sputtering or spitting.
  5. Take it to bits and wipe it all down. You probably don't need to do more than remove the handle and nozzle-cap, release the needle chocking nut and then pull the needle out. Wipe the nozzle cap, nozzle and needle clean with soft, damp tissue. You can normally do this with water, but a small amount of white spirit can be useful too. If you *do* use white spirit, make sure you blow it all out of your brush before pointing it at your models or all the hard work you've done might be damaged. Take an opportunity to rinse it out at the same time.
  6. Get some interdental brushes from wherever you shop for your toothpaste - these are great for reaching into the siphon tube (on a siphon brush), down into the channel that runs from the paint cup to the nozzle (on gravity-fed brush) and various other places to boot. MAKE SURE THAT BEFORE YOU START THAT ANY PAINT THAT MIGHT BE IN THERE HAS SOMEWHERE TO GO! For example, if you're going down the cup towards the nozzle, take the nozzle off first otherwise you'll just force thick, dried paint into the nozzle and bung it up for good. Use these in conjunction with an appropriate solvent (white spirit if you've been shooting oil-based paint or IPA if you've been using water-based paints. White spirit can be useful here too, though). I use the red one on my airbrush.

When to clean:

  1. Whenever you've finished for any period of time of more than a few minutes. If paint dries in the brush, especially in the nozzle, you're in trouble.
  2. Whenever the cup is empty, give it a clean. This is one of the reasons I advocate not overfilling the cup - less paint means more frequent cleaning. The extent of the clean at this stage can be judged by how well the brush has been performing for you.
  3. Whenever the delivery of paint seems to reduce. This can just mean your cup is emptying, but it can mean a clean is required too.
  4. Whenever the paint starts to "sputter" or "spit".
  5. If it ever looks like the paint is coming out as more "water" than "paint". I'm not sure of the science behind this, but there are times when shooting paint when what appears to be coming out is just dirty water - it's like the pigment's been left behind. Also see "It's spitting water!" below.
  6. Whenever you think you need to, or the brush just isn't behaving as you'd like!

Airbrush schematic
It looks like a long and complex process to clean an airbrush, but you'll soon get the whole thing down to about 5 mins tops. Also, you'll learn what your brush needs so you won't have to follow the whole process every time.

If you can find a schematic for your particular airbrush, then please refer to it rather than to the one here. This one isn't the diagram for my brush, but for the most part it's a good match (my brush doesn't have a "Crown Needle Cap" for example) and so it's probably a reasonable match for your brush too, but if you can get the exact diagram, all the better.

Maintain your brush (long story, bear with me):

I was working merrily on my Mighty Fortress project a few weeks ago and was finding that the brush was misbehaving. Paint just wouldn't shoot. I'd followed all my own advice from above but was making little headway, so I decided to go for a big clean. This consisted of all the above plus taking the nozzle off and using an interdental brush to clean the channel from the cup to the nozzle and also having a rummage around to see if I could de-gunk the nozzle itself.

What happened was I twisted my nozzle-spanner at an odd angle and broke the nozzle (the conical "front" snapped off the threaded "back"). The thread stayed stuck inside the brush. 

I was on the right track though - I could see that there was a buildup of paint inside the nozzle. I ordered some replacements and (for good measure) a new needle too. I got the thread out of the brush by taking the handle off, removing the chucking nut and then using a pin-vice to grip the back-end of the needle. Pushing forward and rotating the needle clockwise (as viewed from the back of the brush) unscrewed the nozzle-thread and it came out nicely. I completed my clean with the interdental brushes and waited for the spares to arrive.

When they did I immediately fitted a new nozzle, put my old needle back in and was very surprised to find two things:
  1. The brush still wouldn't shoot well,
  2. The needle was protruding out of the front of the brush. A very painful discovery when I tried to "bubble" it for the first time.
I fiddled and mithered for a while until I resolved to replace the needle. Hey presto - no protruding needle and the brush was shooting well again.

I think what had happened was that the constant flow of paint over the needle had worn it down so it could slide further into the brush than it should. The paint build-up in the old nozzle had mitigated against that slightly, but with the new nozzle in place the old needle just wouldn't function.

It's spitting water:

One other issue I've had from time to time is that the brush can spit water (not paint!) when you're painting with it. You can be laying out a nice, even layer and all of a sudden "GOB!" and your clean, smooth finish is toast (with spit on).

What this often seems to be is a build-up of water in the host that runs from the compressor. Switch the compressor off, unscrew the air hose from the compressor and lift your airbrush high into the air so the hose falls straight to the ground. You may find water comes out - let it drain completely before you carry on.

As a preventative measure, if using a compressor you will probably find that there's a see-through vessel near where your air-hose attaches. That's a moisture trap. It will have a valve (normally at the bottom) which you can push to allow it to drain. I'd advise pushing that valve open with a tissue after every few minutes work.

The all-important final note:

By far the best piece of advice I can give became apparent to me recently. I embarked on a totally airbrush-centric project (my Tau army) in order to become as intimately familiar with the airbrush and rid myself of all those last doubts and fears. Total immersion in the tool and so on...

In order to be as ready as possible for it, I did two things:

I cannot underplay the difference it has made to the ease of use I'm now getting from the tool. I point it and pull back the trigger and paint flows! All of the above issues still occur and all the advice is still valid, but the number of times I have to follow my own advice has been massively reduced.

Almost all the frustration has gone - I'm finally really enjoying using my airbrush!

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