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More Tools and Materials

• Basic Primary & Secondary Color Palette
• Acrylic Retarding ( or Extending) Medium
• Variety of Paint Brushes
• 1-1/2" - 2" Dry Blending Brushes
• Compass or Large Circle Template
• Ellipse Templates
• Earth Red & Yellow (Earth Colors)

You will need red, blue and green for painting nebula in color. A palette of earth tones is useful for planets. And of course you will need portrait colors if your going to eventually include people in your paintings.

A palette can grow by more than just colors. There is a choice between thicker, and more traditional, paints in tubes and somewhat thinner paints now available in jars. Jar colors tend to have a higher pigment (color) to vehicle (acrylic medium) ratio.

In addition there are choices of opaque, translucent and transparent colors. Opaque colors tend to cover and hide the color underneath. Transparent colors should allow the background layer to show through. Translucent are somewhere in between.

I will only briefly discuss paint characteristics since numerous references already exist on this subject. The two most basic measures of a color are its value and hue.

The value is the general brightness or darkness of a color. Imagine viewing the color as in a black and white photograph. The position on a gray scale is the color's value. A theoretically perfect black would be 0.0 and the maximum brightest white would be 10.0. In the real world black and whites are not absolute. Thus a typical white paint might actually be marked as a value 9.6. Middle gray is defined as 5.0 in this system.

Hue, or sometimes refered to as chroma in some systems, is the actual color of the paint. This is more involved since there are more than one color systems. Each paint manufacturer typically distributes literature along with the paints to the art stores. Ask if you do not see it on the shelves with the paints.

Other paint characteristics include lightfastness which indicates how long the colors will retain their quality with age. Last, but not at all the least, is the toxic warning lable. I recommend using only materials labled as non-toxic.

Another usefull material is acrylic retarder or extender medium. This is often used to brush paint nebula and where other special blending techniques are needed. Extender medium slows the drying of acrylic paints. This is especially useful when blending or working larger areas.

Put together a collection of various size and shapes of brushes. You are probably better off to buy better and more expensive brushes over a period of time rather than a cheap set of inferior brushes in one single purchase. An entire book could be written about artist brushes and all their myriad variations. In general, select a number of round-ish and flat- ish brushes of various sizes. Stay with name brands.

Information on brushes can take up an entire text in itself. Most artstores carry only a basic selection anyway.

You will also want some medium size (1-1/2" to 2") hardware store paint brushes. These can be cheaper as long as their somewhat soft and suitable for acrylics. You may want several of these since they are used to blend paint using dry bristles. As one brush becomes loaded with paint you will need fresh ones. Once rinsed they can not be used again until complete dry. Wash the brushes with soap and water. Any dried acrylic paint can be removed by soaking the brush in denatured alcohol. Alcohol is highly flammable and must be used in a well ventilated area away from any flame source.

A compass, and circle and ellipse templates are absolutely vital for painting planets. Common objects around the house are generally not suitable because they lack center and alignment marks. It takes very little misalignment to make an object look skewed and just plain wrong. In fact, later there is an entire chapter devoted to circle and ellipse alignment and placement considerations. So collect as many ellipse templates as your can find.

An alternative to physical drafting aids such as templates , one can use moderately sophisticated computer drawing software. The printed output from the software can then be traced or transferred onto the board. It is best if the software can tilt or rotate ellipse to avoid making many separate printouts. This avoids having to rotate in place and transfer each separately by hand. You may want to secure the template to one edge of the artwork so it can be moved out of the way, yet easily returned to the exact same position for reference.

The Air Brush

• Air Brush
• Air Source
• Air Brush Paints
• Misc. Supplies & Breathing Protection

The airbrush is the ideal artist tool for rendering many celestial objects, such as galaxies, nebula, and some features of planets. Unfortunately, airbrushes and especially an adequate reliable air source are expensive.

Airbrushes can be classified in a few basic designs.

External mix airbrushes flow air over a small opening connect to a siphon tube in the paint jar. The paint and air are mixed outside the body of the airbrush. These are the least expensive and also the least versatile. They are generally not suitable for fine detailed work.

Internal mix airbrushes mix the paint and air inside the airbrush. They are available in what is called, single and double action. These are more expensive and higher quality.

Single action allows control over only one aspect of the paint/air mix. Thus the trigger moves in only one direction. Air and paint are mixed in a fixed proportion.

Double action is probably most popular and versatile. Double action allows control over both the air and paint flow into the internal mixing chamber. The trigger moves down for air and back for paint flow. Double action airbrushes are only slightly more expensive than single action and well worth the increase in control and versatility. But we are not done with our options yet.

Double action airbrushes also come in a selection of bottom, side and gravity (top) feed for the paint cup. This also has effect on cost, quality, and ease of maintenance.

Bottom feed airbrushes siphon the paint from a cup or bottle that attaches to the underside of the airbrush body. Unfortunately this attachment is usually based of the friction of a snug fit between metal parts. I had one experience of a cup partly full of paint fall and spill over the artwork. Luckily the artwork was salvageable but I have since been uneasy about using my bottom feed airbrush when my artwork is nearly horizontal and underneath my paint cup.

Side feed airbrushes siphon paint from a cup attached to the side of the body. They are perhaps the most versatile since the cup can be rotated completely around to any angle. One can paint down, horizontally or even straight up. (Someday I intend to paint space art on a ceiling.) One distinct disadvantage to side feed is they are either right hand or left hand specific. Only a well stocked larger Art store will probably carry left hand models in stock. Most dealers will order one for you but make sure they order the correct model to avoid disappointment and delay.

Gravity feed airbrushes have a reservoir or cup permanently mounted to the top. I am told that gravity feed mechanisms have the least problems with clogging since they do not siphon the paint. But top feed (like bottom feed) limits the angle in which the airbrush can be used without spilling paint from the cup.

For completion sake I will briefly mention the turbo/turbine airbrush. These are expensive airbrushes with sophisticated mechanisms for mixing the paint with the air. Turbines are generally intended for thin media and very fine detailed work. Their marginal improvement in results do not generally justify the significant increase in cost and maintenance.

Once you have decided on an airbrush you must then fit it with a nozzle (tip) and needle size combination that is suitable for acrylics. A medium or heavy flow is usually recommended for acylics. A medium tip and needle will produce finer detail control but is also more susceptible to clogging. Nozzles and needles can also be used together in the "wrong" combination of sizes to produce special spatter effects. (see basic starfields)

Air source

Unfortunately a good reliable air source is more expensive than the airbrush itself. A number of inexpensive and improvised air sources may seem available but compressors and pressure tanks are the only practical ones.

Compressors are cheaper and more portable than pressure tanks. Avoid cheap general purpose paint sprayer compressors. They are very noisy and sometimes require the addition of a regulator to maintain constant pressure. Compressors specifically made for airbrushes are more quite and usually provide an optimal general purpose pressure. Some elaborate set ups are even combined with small holding tanks and automatic shut off that further evens airflow and minimizes wear on the compressor.

Even speciallized "quiet" compressors make some noise and may be louder to a downstairs neighbor that to you. Compressors also have the disadvantage of also compressing moisture that condenses into water droplets in the air hose. These droplets eventually collect and are forced through the airbrush interrupting the otherwise smooth and even mix and flow of paint and air. These produce unpleasant results and continue to occur until the line is disconnected and dried.

One remedy to moisture build up is a device called a moisture trap. Both cheap and expensive moisture traps are available. These must be emptied occasionally and do not guarantee the elimination of the problem.

Pressure tanks avoid all the noise and moisture problems of compressors. But their worst draw back is their expense. Even renting requires a hefty deposit for tank and high pressure regulator. Some setups may require both a high pressure and low pressure regulator for airbrushing. Threaded connections may not match and may involve phone calls and trips to highly specialized hardware or welding supply shops.

Besides being heavy the transportation of a non-empty pressure tank may be legally prohibited by air or even across state lines. But for permanent studio use there is nothing like the ease, convenience, and quiet of tank supplied air.

Airbrush Paints

Tube and jar acrylics must be thinned for airbrush use. Jar acrylics have higher pigment to medium ratio and are preferred to their tube equivalents. The common (and somewhat subjective) guide to thinning paints is to dilute them to a "milk like" consistency. If you plan to save the thinned paint for any length of time then dilute them with distilled water. Tap water can contain minerals and other chemicals that slowly react and deteriorate the quality of the paint. Thinned paints will also tend to separate over time. Shake them well before using. Check for any clumps or sedaments that may clog your airbrush.

Specialized acrylics designed for immediate use in airbrushes are becoming widely available. Their reasonable expense is often worth the delay and guess work of thinning jar acrylics. Some may eve contain additives to minimize clogging. Like all paints stay to established brands to maintain quality, consistency and archival considerations.

Breathing Protection

As more and more exposure data is collected it is becoming evident that inhaled substances can have distant and severe heath effects. Absolutely avoid airbrushing any paints with cadmium or lead pigments. Use only paints labeled as non-toxic. wear the best breathing protection you can afford. If you can not tolerate a mask on your face, try to find a well ventilated place where there is a perceptible flow of air across you work space. Eye protection may even be necessary during heavy airbrushing.

Cleaning

Immediately flush your airbrush with water between colors and after use. Airbrush cleaning fluids are commercially available. These cleaners generally use ammonia as their primary active ingredient. They can be mixed much more cheaply yourself by diluting "sudsy ammonia" that contains detergent.

Clean the airbrush by spraying some ammonia cleaner through it. I have found you can minimize surrounding yourself with noxious ammonia fumes by simply dipping the tip of the airbrush into a pail of water while spraying.

Finish your cleaning by flushing the airbrush with clean water. Check your airbrushes manufacture instructions for any special cleaning directions.

Occasionally you will need to disassemble the airbrush for a compete and through cleaning. Become familiar with the manufactures instructions for dis- assembly and re-assembly. Soak all the parts overnight in denatured alcohol. Use a container that can be tightly closed. Alcohol is highly flammable. Never spray alcohol through your airbrush. An explosive atmosphere can result and can be ignited by any flame or even static electricity.

Additional tips on Airbrushing

Since the airbrush tip does not touch the surface, a specific skill needs to be developed to control spray placement. Practice drawing parallel horizontal and vertical lines. Holding the airbrush with both hands tends to avoid the natural arcing motion when drawing straight lines with only one hand only.

Then draw some grids and practice dotting the intersections. Try underlining and dotting print on newspaper. Also practice painting areas with uniform and graduated fills.

Airbrushing can result in a certain amount of arm fatigue. This is especially noticeable for close detailed work. Take your time and be ready to spread your airbrushing across more than one sitting. (This is where premixed paints are particularly useful for maintaining consistency.) It is better to be patient than botch everything in one last hurried session.

If an accident does occur wipe it up quickly with a damp cloth. It is a good idea to varnish your artwork with acrylic gloss medium between significant steps.

Always keep clean water and towels or rags nearby. I find it very useful to fill a spray bottle with distilled water. You can flush the airbrush by spraying water into the cup or even directly into the opening for the cup. Flush your airbrush with distilled water before putting away to avoid build up of calcium and other minerals normally found in tap water.

Be prepared to purchase needles and nozzle tips on a regular basis since these are easily damage even in gentle usage.

Other Techniques

Of course you may want to place stars in specific locations. Either to form a consilation or some other distinct noticeable pattern. One favored method I to use a toothpick. Round toothpicks are usually tapered to points. Thus they can be cut anywhere along their length to produce different sized dots.

Colors

Generally the farther stars are the more they appear as just plain ole' white.

Stars usually only begin taking on strong colors as they are close or large enough to have discernible disks.

Diffraction Spikes and Rings

The wide publication of deep sky photographs of space has created a common expectation of rings and circles around and lines through bright stars. These are not a part of the star itself but actually distortion caused by the internal construction of reflector telescopes.

These telescopes use a cleaver arrangement of mirrors to compress an otherwise long focal length into a short physical tube length. A small secondary mirror is suspended by vanes in the light path of the larger primary mirror. Some of the star light passes very close to the edge of the vanes, secondary mirror, and the inside surface of the telescope tube itself. This light being quantum mechanical in nature gets scattered by diffraction to produce the spikes and rings around bright enough stars in the image. This is why all the spikes have the same orientation and circles the same size/radii.

In fact any bright point light source will have diffraction spikes and rights when imaged through such a optical system.

Most reflector telescopes use a 4 vane (mechanism) for holding the secondary mirror. This is why the cross pattern is so familiar and commonly expected. Six equally spaced lines/spikes is also commonly acceptable. In principle three and other number of spikes would be possible but tend to be visually distracting and unastetic.

Because diffraction effects occur in the telescope (at the location of the viewer) they are in front of every other object in the image. No part of the effect should be hidden by any foreground object. One possible exception to this rule (and all rules usually have exceptions) is if the cause of the diffraction effect (telescope image/window) is a foreground object itself. (i.e. a view screen on the bridge of a ship would have diffraction effects as part of the view screen itself.)

Painting Rings and Spikes

The spikes are usually slightly thicker at the center (where the star or point light source is) and taper near the edge. They should all be the same length and basically identical.

There is usually one outer ring near the tips of the spikes. This ring might be fainter than other parts.

Closer to the center there can be a second ring or bright solid disk. The center is usually the brightest. Some parts of the pattern will have a soft diffused edge. Others will be hard and sharp.

Their exacting geometric shape and smooth soft quality makes them very difficult to paint by traditional brush. In special cases diffraction patterns can be drawn using a white colored pencil. But an airbrush usually produces the best results.

Colored Pencil Method

A white colored pencil can be used if the rough gesso surface is still exposed. Pencil will not draw evenly on a smooth glossy surface.

Use a good quality artist colored pencil. A sharp point will give you best control. I find it easiest to draw the spikes first. This provides easy guides lines for a circle template. Here once again is the advantage of using illustration or canvas board. you can set a T-square right on the edge of the artwork.

Use a circle template or compass to draw the rings and or disk. edges can be carefully softened using the pencil. Some practice will be needed to get realistic results.

Aibrush Method

Due to its geometry each part of the effect needs to be masked and painted separately. Again I find it easiest to start with the spikes. Use low tack drafting or removable tape. Using a T-square for alignment lay down two strips side by side with a small even gap between them. Mark the tape equal distances from the center where the star is or will be.

Using more tape and newspaper mask off the rest of the artwork. Even the slightest amount of over spray can show up along the edge of a mask that did not completely cover the artwork.

From a few inches away spray the airbrush at the center for a brief moment. It is difficult to judge the effect when airbrushing masked off regions. The usual mistake is to under estimate the amount sprayed and apply too much.

Also be careful to not apply too much spray at one time. You do not want the paint building up too fast and collecting/beading into droplets. These droplets can scatter in the airflow or even run along the edge of the mask. If the mask in not burnished down well the paint can even run underneath creating quite a mess.

Peel up the mask as soon as the paint seems dry to the touch. Allow the paint to dry for couple hours if not over night.

Apply tape similarly to the first spike for the second spike. Cover rest of painting and airbrush. Now you must try and match the amount of spray to that you used for the first spike. You may want to save the tape fro the first mask and keep near by to use as a reference. The old and current tape mask should end up with about the same amount of paint on them. It will be easiest to compare if the two sets of tape are on similar (if not identical) backgrounds. Again let the paint dry slightly and pull up the mask.

There are a number of ways to mask for the circles. The easiest is to use a circle template. Make sure you mask off of cover the other holes on the template. And of course cover the rest of the painting. Airbrush the circle on the template just outside the edge being used as a mask.

Spraying directly on the painting at the template edge may produce too extreme of an effect. It is also harder to control and produce a more even and consistent result. It is probably better to build up the over spray gradually. Inconsistencies also tend to even out on over lapping layers.

Use a smaller circle to mask the bright center disk. This time carefully spray in the center of the circle. Again be careful not to over do the effect.

Clean the template thoroughly when done. It will be difficult to position it if the centering marks are covered and obscured. An ammonia cleaner should be adequate. Too strong of a cleaner such as alcohol might also remove the templates markings.

You may decide that your diffraction effect is too sharp edged and harsh. One solution is to freehand (without template or mask) soften the edges with white paint thinned with both water and medium. Undiluted white paint would probably be too severe. Paint diluted with only water can end up too thin and loose much of its adhering ability.

Keep in mind that thinned white paint does not tend to show up well until it is dry. So give each stroke a few seconds to see the effect.

Thinned white paint does not tend to show up well until it is dry. So give each stroke a few seconds to see the effect.

Spray the center from a slight distance. You may even want to move the airbrush back and away to diffuse the effect. Brush from the center outward along the spike can soften them. You can also achieve softer circles & disks by using a circle template designed for ink pens. These have raised bumps to keep the template slightly above the surface to avoid ink from running underneath. They also let a slight amount of over spray underneath softening the edge. Or you can raise the template itself by using layers of tape or even some coins.

If you are applying diffraction spikes and rings to more than one star try and do each step to all of them at the same time. If the effects over lap and are too close for the width of the tape for spikes you can cut the tape mask to narrow it by placing it down on glass and cutting with a straightedge and sharp craft/art knife. Masking can also be cut on the painting.

According to the directions just given it would take about two days to complete a diffractions effect. At this rate the novelty quickly wears off. It is useful to find ways of speeding the process.

The main problem results from applying any sticky mask to paint that is not yet completely dry. The mask can also pull up over spray that is not sufficiently fixed to the surface. Paint dries fastest in a dry warm and well ventilated location. Drying can also be hastened by placing under a warm light or even with a hair drier. Keep in mind, though, that forced drying works from the top down. The paint may form a well dried skin before completely adhering to the painting surface.

(more about fixative sprays)

Other solutions involve finding cleaver means of combining steps. For example both sets of masking tape can be layered down one on top of the other. Then carefully cut the tape mask for the spikes with a sharp knife. Try and minimize cutting the painting surface beneath. This is on of the advantages to illustration board. It has a thick surface and backing. Some brands are even available in double thickness. It would take determined effort to cut through double thick illustration board.

With practice you can often tell by feel when you are cutting the mask only. Keeping a fresh sharp blade in the knife will help.

Another common airbrush and artist aid/tool is clear acetate. This is available in sheets of different sizes and thickness. Acetate makes excellent semi-permanent general purpose masks. You can make a number of diffraction spike templates from one sheet. Try and pick a thickness of acetate that does not lift up easily from the airbrush spray, yet thin enough to cut easily. Over spray blowing up under the acetate edge can soften the line but is also unpredictable. (feathering?)

One remedy is to spray on low tack removable (or repositionable) adhesive. This material is similar to the stick on type memo note pads.

A technique for creating sharp and more defined diffraction ring is to use a circle template in combination with round dot labels found in office supply stores. Use a circle on the template larger than the dot and position the dot down in the center. Dots may be too tacky for immediate use. Laying them down on cloth and peeling them up a few times on coarse paper or even cloth can reduce their stickiness enough to use on the painting. Of course make sure the edges are not fuzzy with cloth or paper fibers.

Yet another tool are templates specially made for airbrushing circles. These usually include the cut outs from the templates. On could use the cutout from a smaller circle with a large hole to mask a ring.

* Never use any oily or waxy substances on acrylic painting. It may adversely effect future layers of paint from adhering to the surface. These may crack, peel and even bubble with age. In fact oil from skin can build up with a lot of handling. Wash your hands before handling artwork in progress. You may want to rest a towel or cloth under you hand, arm or anywhere your skin may be in contact with the painting for longer than a moment.

In extreme cases cotton gloves may be necessary. These are often available in photography supply stores. Cutting off the finger tips makes the gloves more comfortable. It also provides for a better grip on brushes and tools.

Keep in mind that all diffraction effects are not identical. ????? (Although they should be in the same painting.) ??? differences in telescope construction and exposure produce different results. Experiment with different patterns. For example try and diffuse the outside edge or a ring leaving the inside edge sharp.

* Do not be afraid to apply some artistic license. Something like an unusual diffraction effect could become a trademark of a distinctive style.

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