Airbrushing Demonstration
Eric Holmquist
10/25/11
Airbrushes
Action
Single Action
Single Action airbrushes are set to a fixed air / fluid ratio. Pressing the button controls airflow. Well suited for wash coats of finish like shellac.
Double Action
Double action airbrushes allow control of both airflow and air / fluid ratio. Pressing the button down controls airflow. Rocking the button back increases fluid flow. Ideal for artistic effects.
Feed
Gravity Feed
A cup on top of the airbrush contains the fluid to be sprayed. Typically put a few drops of pigment in the cup. Relatively low pressure requirement.
Iwata Eclipse HP-CS (0.35 mm needle)
Siphon Feed
A jar or bottle below the airbrush, or a side mounted cup provides pigment. The bottle / jar models are more suited to higher volume applications like T-shirt / face painting booths. Relatively high pressure requirement.
Iwata Eclipse HP-BCS (0.50 mm needle, bottom feed)
Iwata Eclipse HP-SBS (0.35 mm needle, side feed)
Fittings
Iwata / Grex
Iwata and Grex airbrushes use 1/8” BSPP fittings, so 1/8” NPT fittings will not screw on. BSPP is a standard fitting available from parts suppliers like McMaster-Carr.
BSPP has a different thread pitch from NPT, and the threads are parallel unlike NPT which is tapered.
Others
Badger and Paasche each have proprietary fittings, and special adapters are needed to connect them to standard BSPP or NPT hoses.
Quick Disconnect
1/8” BSPP Quick Disconnect fittings are available from TCP Global and others which allow for easy swapping of airbrushes or air carvers.
Pigments
Paints
You do not need lots of paint to do a lot of projects. I am still on my original 1 oz bottles for most colors, and have airbrushed dozens of pieces. I got a set of several colors and only recently purchased new bottles for the two colors I use the most.
Transparent
Transparent airbrush colors are the lowest viscosity paints with the finest ground pigments, and allow you to see the wood grain through the tint.
Golden – No thinning required.
Createx – Thinning with transparent airbrush medium often required.
Grex – Thinning with transparent airbrush medium often required.
Opaque
Opaque airbrush colors are higher viscosity with coarser ground pigments. Will obscure the wood grain.
Golden – Thinning required
Interference
Interference colors are almost invisible on light surfaces, and visible on dark surfaces with an iridescent sheen. They are high viscosity with a large particle size.
Golden - Thinning required, larger needle recommended, hard to clean airbrush
Iridescent
Iridescent colors have a sparkle sheen to them. They are high viscosity with a large particle size.
Golden - Thinning required, larger needle recommended, hard to clean airbrush
Dyes
Water or alcohol based dyes are easily applied with an airbrush. As dyes penetrate, they will highlight the grain of figured woods unlike paints which tend to mask the grain. As dyes are based on dissolved pigments rather than suspended pigments like paint or stain, they are non-clogging. Dyes do not tend to be as vivid as paints so a light mist coat of a transparent airbrush color can be used on top of the dyed wood without totally eliminating the benefits of the dye.
There is a benefit to using water based dyes even though they can raise the grain. Once you have a section of the airbrushing complete, you can cover it with shellac and any water based dye will bead up on the shellac and be easily wiped off.
Basic Airbrush Techniques
A few basic airbrushing exercises on a large pad of newsprint is very helpful to develop good control of the airbrush before trying it on a nice turned piece.
Lines
Brush a series of parallel lines in many directions. Practice starting airbrush movement with air on before turning on pigment flow. Turn off pigment flow while airbrush still moving. Keep air on the whole time.
Try to maintain consistent line width and length.
Try to lay down a progression of line widths
Dots
Draw a large checkerboard pattern on the paper and practice applying a dot exactly at each intersection.
Try to make the dots consistent in size
Try to make a progression of dot sizes
Play connect the dots
Fades
Fade one color from light to dark. This can be done by a combination of spray distance or pigment flow.
Try both methods and combinations
Try fades in different directions
Blends
Fade two colors from dark to light into each other from opposite directions. Start with blends of primary colors (Red, Blue, Yellow)
Try two color blends (i.e. Yellow to Red, producing orange in the middle)
Try to produce a complete color wheel passing from Red through Orange, Yellow, Green, Blue, Purple, and back to Red.
Masking
Masking is used to achieve sharp edges. Masks can either be hand held or applied to the work.
Pin Striping Tape
Very flexible pin striping tape is available in thin widths (1/64th through ¼”) the most commonly available is 1/8” in most art and office supply stores.
Frisket
Frisket is a low tack plastic film that covers a large surface. Frisket is easily cut with a craft knife. Available in most art supply stores. Comes in either paper backed or roll form. The paper backed form can be run through a copier to get an image on it. Comes in a clear of matte style. The matte style can be drawn on with a pencil.
A common practice is to use a small skew / spear point wood burner to outline an area to mask, then use the burned groove as a cutting guide for the frisket. For designs where the burn line would not be desirable, using pin striping tape to outline the area then frisket over that, cutting on the pin striping tape will help avoid and cut lines on the turning.
Automotive Painting Tape
The green automotive painting tape is preferable to the blue stuff or regular masking tape. The blue painters tape or regular masking tape will tend to leave adhesive on the work.
Acrylic Acetate
Acrylic Acetate is thin clear film with no adhesive. It is good for making hand-held masks. Typical uses are in re-masking or punch masking. Punch masking uses the huge variety of paper punches to punch out all sorts of shapes.
Plastic Signs
The plastic sign signs available in most hardware stores (“Beware of Dog”, “Car for Sale” etc.) are good for simple masks. The material is a bit too thick to punch or cut details out of with a craft knife, but simpler shapes cut out with scissors work really well.
Tools and other equipment
Craft knives
The basic fixed blade craft knife is good for cutting frisket or acrylic acetate. A variant on this called a swivel knife, allows the blade to rotate in the handle while cutting, which can sometimes be easier to use following curves.
Cleaning Brushes
Small brushes a bit like old pipe cleaners are helpful in cleaning airbrushes.
Compressor
A small compressor is needed for airbrushing. It does not need a lot of capacity, between 0.5 and 0.75 scfm at 50 psi is adequate for most airbrushing. Generally most airbrushing can be done around 30 psi, but heavier paints and siphon feed airbrushes can require higher pressure. Typically light weight (under 10 lbs) and around $100. With a secondary regulator, a larger shop compressor can be used.
Regulator / Water Trap Filter
A small regulator / water trap filter assembly set to around 30 psi and allow you to leave your compressor at full pressure. Around $20 plus a bit more for air fittings.
Finishing
Clear Coat
Without a clear coat on top of it, the airbrushed design looks very flat and uninspiring. Some sort of clear gloss finish is needed to make the colors look really nice. Keep in mind that many finishes tend to add a yellow / gold tint. So careful selection of a finish is essential.
Minwax Wipe-on-Poly puts down very thin coats. If you sand between coats, you will scratch the design. According to Minwax tech support, it takes 3 to 4 coats of Wipe-on-Poly to match the film thickness of 1 coat of brushed on Fast Drying Poly, so you should apply a minimum of 9 coats before light sanding. Poly will slightly yellow shift the image.
Vermont Natural Coatings PolyWhey is a very clear whey protein based waterborne polyurethane, with no color shift that I have been able to detect. As a brush on product, it builds faster than Wipe-on-Poly. I can put on three coats in a day then lightly sand with 320 / 400 the next day and buff. Brushed, recoat time is 2 hours. PolyWhey can also be applied with an HVLP spray-gun using a 1.3-1.5mm needle. Use 30 minutes between spray coats and at least three coats.
Target Coatings EM6000 is a very clear waterborne lacquer, with no color shift that I have been able to detect. Apply with an HVLP spray-gun using a 1.3-1.5mm needle. Use 30 minutes between coats and at least three coats.
General Finishes Enduro is reputed to be very similar to Target Coatings EM6000 in clarity and behavior. I have not tried this product over airbrushing yet, but have used it on pens and it is a very durable finish.
Nitro-cellulose Lacquer is very clear initially but has tendency to yellow with age. The fumes from these finishes are quite toxic and unpleasant.
Image Sealing
The image is very prone to smearing, so a light mist coat of de-waxed shellac is very helpful to protect the image before applying any wipe on or brush on clear coat. Practice on some flat scrap wood to get a feel for how much shellac is necessary to protect the design.
The chemicals used to stabilize some liquid shellacs (Like Zinsser) for long shelf life can cause a reaction with some waterborne finishes causing them to craze (form lots of cracks like a broken car window). If using waterborne clear coats, you are better off making your own shellac from ultra blond flakes. Make it in small batches (I use 6 oz preserve jars)
You can directly spray most finishes over the image if the first coat is a very light mist coat. This light mist coat will not cause the image to bleed or run as long as you give the image some time to dry first. This initial mist coat does not count as a coat, so if the product recommends multiple coats, only start counting after that mist coat dries sufficiently to re-coat.
Suppliers
TCP Global
A good general supplier of airbrushing and spray gun equipment and supplies.
Bear Air
A good general supplier of airbrushing equipment and supplies. Located in Easton MA.
Dick Blick
A good general art supplier.
Target Coatings
Finishing manufacturer.
http://www.targetcoatings.com/
Vermont Natural Coatings
PolyWhey manufacturer
http://www.vermontnaturalcoatings.com/
