October 28, 2012

Airbrush newbie info

When browsing on airbrush forums there is one problem that bugs newbies always: the spraying of fine lines. In the process of mastering this technique, the possibility to create more types of art comes within the reach of the artist - as the artist's skill increases, the level of art goes up. All experienced artists at one point were newbies and had to find ways to grow beyond this stage. There are several matters that affect the ability of the airbrush to produce a fine line:

  1. The quality of the airbrush
  2. The quality of the paint
  3. The adjustment of the airbrush
  4. The mix-ratio of the paint and added liquids
  5. The quality of the compressor
  6. The setting of the compressor's air pressure

Of course there are more means to allow the airbrush gun to spray finer lines, but for newbies who work with standard, unmodified airbrushes the above mentioned points will do for the time being. This blog entry is meant for newbies who want to have a nice start and avoid purchasing the type of gun, paint and compressor that does not suit their intention of airbrushing a particular type of art work.

The quality of the airbrush

Don't expect a cheapo Chinese airbrush to be capable of spraying fine lines or produce a consistent spray jet. If you're serious about mastering the art of airbrush it pays off to spend a little more money to buy a decent brush. I'm not saying all Chinese airbrushes are bad, but most of them will only give you headaches and spatters. The established brands all have starter airbrushes that work quite well. Iwata's Neo is a quality airbrush, Badger - that has more than excellent customer service - has several types, Harder & Steenbeck has the Evolution which is a versatile tool etc. Explore the airbrush forums to make your choice based on user experiences, but don't base your choice on merely one of them. Newbies are in the process of learning how to handle their airbrush and a good gun that is poorly adjusted will not spray well. They may report problems that are easily resolved. Find out who the more experienced users are - look at their gallery to see at what level they are airbrushing - and consider their advice and tips. A very good forum is the Airbrush Forum, where there are many experienced members prepared to help. Forums related to the scale model hobby often contain useful info on airbrushes, paints and compressors as well.

Click to visit the forum

Starter airbrushes have nozzle sizes of 0.3 mm which allows most paints to be sprayed in a decent and controllable way. The Iwata Neo is an example of an airbrush of this category. Spraying larger areas can be done with these types and detail is also possible, but in order to spray really fine detail it is almost inevitable to use high-end guns like the Badger Krome, Velocity or Spirit (all 0.21 nozzles), Harder & Steenbeck Infinity (0.12 and 0.2 nozzles), Evolution (0.2 and 0.4 nozzles) or airbrushes from the Iwata Micron series (0.18 and 0.23 nozzles, depending on the type) that are the undisputed top of the bill, but also quite expensive. The list is of course incomplete and I would encourage you to visit airbrush forums before making a choice.

I suggest you visit svee's Youtube channel to gain really good information about all airbrush related materials and use. There are more than a hundred clips on topics related to airbrush in this channel. Besides providing a wealth of information they are quite fun to watch. So if you have a short attention span you should definitely take a peek at the video clips created by svee instead of arduous ploughing through written documentation.

Iwata airbrushes

The quality of the paint

The quality of paints is mainly determined by the size of the pigment particles. Paint has to pass through the narrow space between the needle and nozzle and bigger pigment particles have more trouble doing that than finely grained pigments. The type of solvent (in which the pigment particles are dissolved) also affects the flow of paint. There are two types of solvents: thinner based (also called urethanes or uros) and water (waterborne paints). Uros do by far the best job of evenly dissolving pigment particles, but inhaling their fumes will not contribute to the artist living a long and healthy life. Waterborne paints are less harmful to your health, but have a chaotic way of distributing pigment particles in mixtures based on water. To improve this shortcoming, additives are thrown into the mix, but so far none of those has managed to equal the properties of thinner based mixtures.

The Createx paints - Auto-Air, Wicked (and various Detail versions) - are heavily pigmented paints. In other words the pigment particles in the paint are quite large. It means they do an excellent job in coloring a surface, but it requires high mix-ratios (which means the use of a lot of water in which the paint is mixed) are necessary to jet them out of the airbrush in a decent way. It also means air pressures have to be higher than is the case with paints that consist of finer grained pigments. Hig air pressures in airbrush means 20 psi and upwards. High mix-ratios come down to 1 part of paint in 5 - 10 parts or more of paint.

Com-Art paints that are waterborne paints like Createx, have a finer pigmentation and can be sprayed with air pressures of approximately 10 - 14 psi and mix-ratios of 1 part paint in 5 parts of water.

Holbein Aeroflash waterborne acrylic airbrush paint

Excellent quality paint that have fine pigments are E'tac, Lukas Illu-Color and Holbein Aeroflash. E'tac has a lot of additives that need to be mixed into the paints, which makes grasping how paints work (best) a little difficult. Holbein's Aeroflash paint can be mixed with water (between 1 : 10 and 1 : 30 mix-ratios) and used right away. The finer pigmented paints are a little more expensive than the cheaper, coarsely pigmented paints, but they flow much better and cause less tip dry (the clogging of paint in the tip of the needle / nozzle area of the airbrush). Please bear in mind that these values are indications; more experienced artists all have their own formulas with which they feel comfortable. But these indications are a good start for newbies.

And then there are the black and white colors that are traditionally more difficult to spray than any of the other colors because of the coarse size of their pigments. Here you find an excellent compare / test of various white paints.

One tip for artists who use waterborne paints that will help making spraying fine detail less of an ordeal, is to add one drop of ox-gall in the paint cup of the airbrush. It will make the paint flow better and give the colors a subtle shine, once sprayed. Ox-gall is often used by hairy brush artists who use oil paint. The same ox-gall they use works fine in airbrushes.

The adjustment of the airbrush

There is not a lot to adjust in most airbrushes for newbies. Just make sure the air cap is not leaking, i.e. not sucking false air, which results in rythmic impulsed spraying instead of a controllable, steady jet of paint and water or solvent. If the gun sprays impulsed jets, apply teflon tape or liquid packing to the threat on the airbrush housing. In the image below the dark red / brownish part is the air cap.

Tip of an airbrush

If the airbrush sprays paint while the trigger is all the way to the front and you are unable to not let it spray small amounts of paint, turn the needle rocker inwards into the airbrush housing (one or more turns) and continue to do this until the gun does not spray any paint while the trigger is all the way to the front end. It will increase the spring tension somewhat, but allow you better control over the process of airbrushing. The image below shows all the parts of an airbrush; the colors of the parts correspond with those in the legend below the drawing.

Parts reference of an airbrush

Manufacturers indicate their parts in their own way; there is no name giving standard in this. The needle rocker to which I referred in the previous paragraph is in rose color in the image above. Paasche calls it needle support, Iwata calls it needle chuck, Badger calls it needle tube and Harder and Steenbeck (surprisingly) has very little visual and textual info on the parts of their brushes, but the principle of venturi based airbrushes is the same with every brand.

If the airbrush become unpredictable and stops giving paint and air after which it suddenly sprays too much, then it is time to clean it. You may to prevent reaching this stage, since it has the potential to ruin your art work. If the gun shows the first signs of becoming difficult to control and sprays unsteady and thicker lines than when you put fresh paint in the paint cup, start cleaning.

Usually it is enough to screw off the back end of the gun, take the needle out and clean it with a cloth or your fingers, but it this does not help, you may want to take a peek at this Youtube video clip to clean it thoroughly.

Mix-ratios of water and paint

Most airbrush artists will be using waterborne paints, so this is what will be discussed in these paragraphs. Mix-ratios have a direct relation to the particle size of the pigments and air pressure. Paints with coarse pigments will require higher air pressures and larger nozzles. Paints with small sized pigment particles can be sprayed through smaller nozzles and lower air pressures, resulting in finer lines. Never believe the straight out of the bottle advice that some paint manufacturers give you; it only makes them sell more of their product. Always dilute your paints, like already mentioned in the previous paragraphs. The video clips above, will give you clear visual demonstrations of how to mix paint.

Most airbrush paint can be diluted with other liquids than water as is shown in this video clip. Apart from indicating useful liquids the guy also tells what liquids are best kept far away from airbrushes. He does a little test in the video to prove his claims, so it is pretty safe to follow his advice. Visual demonstrations work best for most people; this blog is intended to be a mere reference for artists new to the airbrush business.

The quality of the compressor

For general airbrush use there are two types of compressors that qualify for use at home. These qualities are supplying a sufficient amount of air in a regular, non-pulsating supply while not making a lot of noise. The first and better (also more expensive) type is the piston compressor, that is similar to the type you find in refrigerators. The compressor's tank levels out the pulsations inevitably caused by linear piston movement. In smaller types, the tube shaped tank also has the function of the handle to lift the (portable) compressor). Besides a an air regulator and air pressure indicator gauge, they should also have a water separator that removes moisture (water and slush) from the air before it reaches the airbrush. Piston driven compressors are lubricated with oil that needs to be changed or replenished at regular intervals.

Piston type compressor

Once in every while the tank needs to be drained from slush through a bleed valve positioned near the bottom of the tank. Water and slush in the air will make airbrushes spray irregular and affect mix-ratios while causing paint to adhere badly to the surface the artist is spraying on. Established brands are Sil-Air, Hansa and Euro-Tec. Airbrush manufacturers like Iwata-Medea, Paasche, Badger and Testor (Aztek) also have their own line of compressors.

Diaphragm compressor

The other type of compressor builds up pressured air by a diaphragm that is moved by a notched disk. It requires no lubrication. The amount of air supplied is less than that generated by piston type compressors. These diaphragm type compressors are lighter and cheaper, but good enough for spraying small art work with low air pressures.

The setting of air pressure

The basic air pressure can be controlled in three places (with some type of airbrushes). There is the air regularor on the compressor, a small separate regulator that can be placed between the air hose and the airbrush and some guns have a built in regulating mechanism, like is the case with the Iwata HP-BH.

Basically the basic air pressure has to be adjusted for every session. The varying conditions of the paint you use, the mix-ratio and room temperature, air humidity all affect the best possible setting. When spraying with ultra low air pressure and extremely diluted paint ( 1 : 10 to 1 : 20 = paint : water) I adjust the air pressure to just high enough to drive out the mixture. Too high pressures will not allow you to spray ultra-fine lines, too low pressures will make the spray inconsistent and unpredictable. Artists have to find the correct setting each time, but you will soon learn the range in which the best setting will be found.