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Painting With Spray Cans |
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By Ron Bell, #12907 |
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We've already covered painting with brushes. The next step is to learn to use spray cans. These are convenient, but can be expensive in the long haul. However, if you cannot or do not want to lay out the cash for an airbrush and all its accoutrements, this may be the way to go for now. Spray cans are paint diluted to a sprayable consistency in a can with a pressurized propellant, usually an inert gas of some sort. The propellant forces the paint out of the can, through a spray nozzle that changes the paint to an aerosol spray. No mixing, thinning, or clean up. No muss, no fuss. But, like all things, there are pluses and minuses and do's and don'ts. So, let's get started. These paints can be purchased in many places ranging from hobby shops to car repair supply stores to discount houses. The paint in each location is basically the same, but each is also a little different. The stuff you get at a car repair shop is probably a lacquer and since lacquer can damage plastic, you have to use all the care you would normally use with a lacquer. Unless you're doing high gloss car finishes or painting metal, it's probably best for now to avoid these. At the discount houses, you can go from the house brand up to some high‑end stuff. They sell both lacquers and enamels, so read the labels before you buy. The colors here are probably more suitable to painting a house than an F‑16, but you can get a lot of mileage out of the house brand flat and gloss blacks and whites and some of the other basic colors. Being as these are some of the most inexpensive aerosols you can get, they are useful for primer and sanding coats. They're also good if you have to do a lot of painting of one color or if you have to paint a large area. That's what they're made for. At the hobby shops you'll find paints designed for plastic models. Beware, if you wander over into the model railroad area or RC planes, you might find lacquer sprays, so it's best to stay in the plastic model area for paints. This is where you'll find paints designed to meet the needs of the plastic modeler. There are flats, glosses, metallics and now metalizers with colors for cars, planes, military vehicles and other subjects. This is where you will get most of your finish color coat paints. Unfortunately, they are also the most expensive. If you figure it costs about $4.00 for approximately 3 oz., that's around $170 a gallon! Fortunately, that 3 oz. can will spray several models and that $170 comes in $4 chunks. Now you've got your paint and want to get started. Basic Techniques: ‑ Shake it well. There's a little ball bearing in the can that's used as an agitator. Shake it until that moves freely and then keep shaking for a minute or so. This is important with all spray cans but is critical with metallic and metalizers. If you don't, your paint will just not cover well or may not have the correct color tone. ‑ Make sure the nozzle is aligned correctly. Some cans have a dot on the top rim. Make sure the nozzle is pointed over that spot. If there's no dot, don't worry. One other thing, make sure the nozzle is spraying AWAY from you. ‑ Keep the can about 12‑18 inches from the surface to be painted. In a sweeping motion, start spraying before the first part and keep spraying until shortly after the last one. This will avoid the paint pooling where you start or stop. ‑ Spray in many light passes, not one heavy pass. Let the paint build up gradually. If the surface ever starts to look "wet", stop. If you apply more paint now it may run or dry like the surface of an old grapefruit. Let the surface dry for a while before you do the second coat. ‑ Wait at an hour or so between coats, but not longer. With some paints, if you wait longer than that, you have to wait 24 to 48 hours or the paint will not dry well and may crack and/or peel. Read the directions on the can to know for sure. ‑ When you're done, let the paint set before you handle it. Not dry, set. In most cases that means it doesn't smell like paint anymore but for gloss paints it can take up to a week. Test the surface of gloss paints by lightly touching it after a day or two. Until it's set, it will almost feel vinyl‑like or rubbery. There's only one exception to this and that is if you have masked any parts (see below on masking). ‑ After a painting session, turn the can upside down and spray until no more paint comes out. This clears the nozzle and reduces the chance of a clog. Hints and Tips: ‑ If it's cold or the can is running low on paint, try putting it in some warm (NOT HOT) water for a minute or so. This will cause the propellant to expand and provide the extra pressure needed to get out those last few drops of paint. Be careful here, though. Don't leave pressurized cans in hot water or you'll be picking shrapnel out of yourself and cleaning paint off the ceiling. Also, before you try to paint the model, test the spray to make sure you are getting a good flow of paint. ‑ Most aerosol can nozzles are removable. If you get a clog, take it off and soak it overnight in paint thinner or better yet, lacquer thinner. This will usually dissolve the clog. Be careful when you put the nozzle back on. If you press too hard, you'll get covered with paint. ‑ Spray in a well‑ventilated area and in a place where you don't mind if everything gets paint on it and wear a respirator or mask. With aerosol cans, there is a LOT of over spray and you don't want to breathe that stuff. In addition, the solvents will be evaporating in the air and you want to vent them safely without fear of combustion. ‑ Get all the parts you need to paint a particular color together and paint them all at once. This will reduce paint wastage and at $170/gal, we want to reduce wastage. Masking: This is a much more involved process than it is with an airbrush, primarily because you have much less directional and volume control with a spray can. The paint is going to go everywhere and in equal amounts. For example, if you were painting the waterline of a ship with an airbrush, you could just mask the waterline and a little above it and then spray the area to be painted. The paint will go where you point the airbrush and in the amount you select. However in painting that waterline with an aerosol can, you will need to mask ANYTHING you do not want painted and that includes anywhere that is exposed. Over spray will go everywhere in a cloud, so be careful to close up all gaps and folds in your masking. To save expensive masking materials, use the good stuff to get your fine edges, then use cheaper painters tape, paper towels or whatever to cover everything else. You can produce sharp or soft edges with aerosol cans. It just takes two different kinds of masking. For a sharp edge, put down the tape or whatever firmly on the line to be painted to. If this is the case, you will need to remove the masking BEFORE the paint sets. If you don't, the paint may stick to the masking more than the model and could chip or peel off. Wait until the paint is dry to a gentle touch and then carefully and slowly remove the masking. Don't put any pressure on a newly painted surface or you'll wind up with fingerprints in your paint. For a soft edge, you have a few options. Try cutting a template of the area to be masked out of card stock and hold or fasten it so there is a gap under the edge. The wider the gap, the softer the edge. Spray straight onto the mask or away from the gap. Never spray 'into' the gap, this will negate the entire process and may cause paint build‑up under the mask. Another technique I've seen is to use a tiny drop of white glue to hold down a tuft of cotton. Let the glue dry and then paint. The cotton provides a soft edged mask and the white glue will just pop off. If you use this technique, don't put the paint on too heavily as it will wet the cotton and embed its fibers in the finish. To produce irregular spots or patches, try cutting a hole in a piece of card stock and holding it over where you want the spot. Lightly spray through the hole and you'll get a soft edged spot. Experiment and you'll find lots of new ways. Just remember the over spray problem and keep things covered that you don't want painted. Metallics, Metal-flakes and Metalizers: The oldest one of these three is metallics. These are paints with names like gold, silver, brass, aluminum, etc. They are regular paints and they are the color of the metals they represent. However, they don't actually LOOK like the metal. If you want to make an F‑100 look like a real natural metal century series aircraft, silver paint will get you the right color, but not the right look. It will just look like a plane painted silver. These paints are applied as regular spray paints except you should spray them on just until the surface looks wet. Go slow and be very careful to avoid drips, sags and runs and use repeated light passes just until the surface is smooth and 'wet'. Then stop. It's best at this point if you can move the piece around through several axis for a few minutes. This means turn it, rotate it, invert it, etc. Keep it moving to avoid the paint sagging or dripping. Do this for a few minutes until the paint starts to dry, then set the part down so the paint isn't touching anything and don't touch it at all for at least a day. Metallics take a long time to set. They may appear, smell and feel dry, but just when you think it is, you'll find your fingerprint in it. You may be able to gently handle it in a day, but give it plenty of time to set up as you would a gloss enamel. Metal-flakes are colored paints with tiny flakes of variously colored metal pigments in them. Colors like Candy Apple Red, Buick Engine Blue, Rootin' Tootin' Raspberry (No, wait. I think that last one was a Kool-Aid flavor.), are examples of metal-flakes. These are used mostly in automotive finishes. They are applied just like regular spray can paint. However, some metal-flake paints are translucent. These are mainly the Candy Apple types, but some others are as well. With these, the pigment to carrier ratio is very low. If you try to use them like normal paints, it will take dozens of coats to cover and may never look right. You have to lay down a base coat of the appropriate gloss color first, then apply the metal-flake over that. This will give you the coverage you need and provide the depth and luster of the metal-flake paint. Make sure your base coat/s are thoroughly dry, smooth and glossy for the best possible finish. Metalizers are tiny flakes of metal suspended in carrier. Now, don't think you actually have a little bottle of titanium flakes in your hand, for example. It's just some metal that is the same color as titanium. These are the best simulators, paint-wise, of actual metal. They are a specialty in themselves and take practice to apply correctly. Some require an undercoat, some prohibit an undercoat. Some have to be buffed, some not. Some have metal dust you rub in, most do not. Some won't work over filler putties and some will but only if the putty is sealed first. There is, however, one thing they all have in common and that is the surface must be absolutely, positively, completely smooth and clean. The smallest scratch will show as will the tiniest mote of dust. I won't go into all the details here as that would be an article in itself. Just let if be known that if you really want to simulate metal from a spray can, this is the stuff you want to use. Follow the manufacturer's instructions to the letter and practice. So, that's a quick primer in spray cans. Remember that all the basics of painting still apply. Prepare the surface well, primer and sand lightly between coats (except with metalizers as directed), and keep the surface clean and dust free. Spray cans will enable you to do finishes not possible with brush painting. With a little experience, you'll find your own ways of doing this as well. © IPMS Eddie Rickenbacker Columbus 2002 |
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