12-24-2008, 12:46 PM
If you plan your painting carefully, there's little or no need to clean it between colours, although that does depend on what you're painting and the colours involved.
I almost never use a colour straight from the bottle - of course it needs to be thinned for spraying, but I usually add some other colours to the mix, too. For instance, if I'm painting box cars (in my chosen era, almost all were "boxcar red"), I'll add a little red or orange, or maybe some zinc chromate primer, or perhaps some brown or black to the out-of-the-bottle boxcar red. After I've painted a few cars (or sometimes after only one - the B&O, for instance, used an especially reddish boxcar red, so I'd paint that car first with a colour that I think is appropriate. The next five cars might be for NYC, which favoured a more brownish shade - add some brown or black to the mix, then carry on.) I use a Paasche VL, double-action brush, and use the paint cup only for spraying thinner through the brush at the end of a painting session. I discovered early on that PollyS, PollyScale, SMP, and Floquil bottles all fit on the lid with the pick-up tube, so I clean and save these bottles as I use up the original paint from them. At any given time, I have about two dozen bottles of thinned paint available for use. If you don't have additional bottles that fit your particular airbrush, they are well worth the cost if you do any appreciable amount of airbrushing.
To switch paint colours using a double action brush, leaving the compressor running, unscrew the bottle from the cap, (with the cap still connected to the airbrush), then, before removing the bottle, lift the airbrush until the bottom of the pick-up tube is above the surface of the paint, then pull the trigger back completely without pressing down. This will allow the paint in the pick-up tube to drain back down into the bottle. Remove the bottle, hang up the brush for a second, and re-cap the bottle. If you're going to use a similar colour next, wipe the exterior of the pick-up tube with a rag, then depress the trigger to clear the brush of any colour still in it from the previous spray, then attach the next bottle of colour. Spray the first shot or two on some newspaper to let the new colour rinse away all traces of the previous paint from the interior of the brush.
A typical spray session might go like this: First, Glosscote some cars for decalling, then overspray some already-lettered cars with Dulcote. Next, paint the sides of a white MDT reefer, followed by two FGEX yellow reefers, and four PFE orange reefers. With the compressor warmed-up, a dozen boxcars are next, in varying shades of boxcar red, followed by some black hoppers and gondolas (all in varying shades of "black" - all lightened to some degree from what comes out of the bottle, and many "tinted" with other colours). When the painting is done, you can continue on with weathering, using severely thinned colours. I like to overspray most lettered cars with a colour similar to, but not exactly like, the base car colour. Do this step first (the extra thinner in the weathering paints will clean the airbrush sufficiently for most colours, although I don't spray clear finishes or light colours such as white or yellow after doing darker colours without disassembling and cleaning the airbrush - no point in pushing your luck. The rest of the weathering colours, generally, are applied in order from darkest to lightest, but you should suit this to the particular car and to the effect which you're seeking. I try to avoid overspraying weathered cars with a final flat finish, as I feel that it makes the end result too uniform. Sometimes, though, especially with chalk weathering, this is unavoidable. I recently painted, lettered, and weathered some cars, then "patched" them for re-weigh data. Since the new data was in the form of decals, I had to spray the already weathered car with a flat finish to hide the decal gloss. A little more very light weathering helped to break-up the uniformity of the finish, but I think next time that I'll mask the cars so only the new lettering will get an additional clear flat finish.
When I've finished for the session, I dump some thinner into the colour cup, then attach it to the brush while the trigger is fully depressed and fully pulled back, shooting at least half the thinner through the brush before shutting down the compressor. The instructions that came with the airbrush suggest placing your fingertip over the needle tip while spraying the thinner, in order to force it back into the air chamber, but I have found this to cause more work once the brush is disassembled. It's also probably not too good for the seal around the needle, either.
I disconnect both ends of the hose, and hang it up, uncoiled, with both ends down - this allows any moisture to drain from the hose before your next painting session. Drain the in-line moisture trap too, if required. Remove the handle from the rear of the airbrush and set it aside.
I next re-fill the colour cup, setting it in the spray booth (I leave the fan running for an hour or two after painting), then drop the air cap, air cap body, and the tip into the cup. Next, remove the locknut and withdraw the needle from the front (spray end) of the brush - this avoids leaving paint residue in the area of the packing washer. Set it aside, then unscrew the needle adjusting sleeve and withdraw it, along with the needle support, and the spring. Set aside the the adjusting sleeve and spring, as these should not require cleaning - if they do, you need to replace the needle packing washer. Lift out the finger lever assembly and set it aside.
Take a pipe cleaner, dip the tip in the thinner in the colour cup, then feed it through (from the rear) the needle passage in the airbrush body shell. Next, feed it through the paint passage of the body shell, starting from the lower end - it will curve and exit from the front of the needle passage - again, pull it through completely. Use a clean rag to wipe off the exterior of the shell, then set it aside. Dip the pipe cleaner into the thinner again, then feed it through the needle support, starting at the front and drawing it through completely. Use it, or a rag, to wipe the rocker assembly if necessary. I keep several cans of lacquer thinner handy, each one for a specific use only. Using the one marked "Cleaner", I dip one end, then the other, of the needle into the can, then wipe it with a clean rag, then use the needle to fish the parts out of the colour cup. These need only to be wiped dry, then the airbrush is re-assembled. The slightly dirty thinner left in the colour cup is dumped into the jar that I use for styrene cement, or into the bottle for cleaning brushes -whichever needs a re-fill.
If you clean the airbrush immediately after painting (I do it even before removing masking tape from any models which I've just painted), you'll never need to spend more than a couple of minutes on this task, and your airbrush will look and perform like new.
Wayne
I almost never use a colour straight from the bottle - of course it needs to be thinned for spraying, but I usually add some other colours to the mix, too. For instance, if I'm painting box cars (in my chosen era, almost all were "boxcar red"), I'll add a little red or orange, or maybe some zinc chromate primer, or perhaps some brown or black to the out-of-the-bottle boxcar red. After I've painted a few cars (or sometimes after only one - the B&O, for instance, used an especially reddish boxcar red, so I'd paint that car first with a colour that I think is appropriate. The next five cars might be for NYC, which favoured a more brownish shade - add some brown or black to the mix, then carry on.) I use a Paasche VL, double-action brush, and use the paint cup only for spraying thinner through the brush at the end of a painting session. I discovered early on that PollyS, PollyScale, SMP, and Floquil bottles all fit on the lid with the pick-up tube, so I clean and save these bottles as I use up the original paint from them. At any given time, I have about two dozen bottles of thinned paint available for use. If you don't have additional bottles that fit your particular airbrush, they are well worth the cost if you do any appreciable amount of airbrushing.
To switch paint colours using a double action brush, leaving the compressor running, unscrew the bottle from the cap, (with the cap still connected to the airbrush), then, before removing the bottle, lift the airbrush until the bottom of the pick-up tube is above the surface of the paint, then pull the trigger back completely without pressing down. This will allow the paint in the pick-up tube to drain back down into the bottle. Remove the bottle, hang up the brush for a second, and re-cap the bottle. If you're going to use a similar colour next, wipe the exterior of the pick-up tube with a rag, then depress the trigger to clear the brush of any colour still in it from the previous spray, then attach the next bottle of colour. Spray the first shot or two on some newspaper to let the new colour rinse away all traces of the previous paint from the interior of the brush.
A typical spray session might go like this: First, Glosscote some cars for decalling, then overspray some already-lettered cars with Dulcote. Next, paint the sides of a white MDT reefer, followed by two FGEX yellow reefers, and four PFE orange reefers. With the compressor warmed-up, a dozen boxcars are next, in varying shades of boxcar red, followed by some black hoppers and gondolas (all in varying shades of "black" - all lightened to some degree from what comes out of the bottle, and many "tinted" with other colours). When the painting is done, you can continue on with weathering, using severely thinned colours. I like to overspray most lettered cars with a colour similar to, but not exactly like, the base car colour. Do this step first (the extra thinner in the weathering paints will clean the airbrush sufficiently for most colours, although I don't spray clear finishes or light colours such as white or yellow after doing darker colours without disassembling and cleaning the airbrush - no point in pushing your luck. The rest of the weathering colours, generally, are applied in order from darkest to lightest, but you should suit this to the particular car and to the effect which you're seeking. I try to avoid overspraying weathered cars with a final flat finish, as I feel that it makes the end result too uniform. Sometimes, though, especially with chalk weathering, this is unavoidable. I recently painted, lettered, and weathered some cars, then "patched" them for re-weigh data. Since the new data was in the form of decals, I had to spray the already weathered car with a flat finish to hide the decal gloss. A little more very light weathering helped to break-up the uniformity of the finish, but I think next time that I'll mask the cars so only the new lettering will get an additional clear flat finish.
When I've finished for the session, I dump some thinner into the colour cup, then attach it to the brush while the trigger is fully depressed and fully pulled back, shooting at least half the thinner through the brush before shutting down the compressor. The instructions that came with the airbrush suggest placing your fingertip over the needle tip while spraying the thinner, in order to force it back into the air chamber, but I have found this to cause more work once the brush is disassembled. It's also probably not too good for the seal around the needle, either.
I disconnect both ends of the hose, and hang it up, uncoiled, with both ends down - this allows any moisture to drain from the hose before your next painting session. Drain the in-line moisture trap too, if required. Remove the handle from the rear of the airbrush and set it aside.
I next re-fill the colour cup, setting it in the spray booth (I leave the fan running for an hour or two after painting), then drop the air cap, air cap body, and the tip into the cup. Next, remove the locknut and withdraw the needle from the front (spray end) of the brush - this avoids leaving paint residue in the area of the packing washer. Set it aside, then unscrew the needle adjusting sleeve and withdraw it, along with the needle support, and the spring. Set aside the the adjusting sleeve and spring, as these should not require cleaning - if they do, you need to replace the needle packing washer. Lift out the finger lever assembly and set it aside.
Take a pipe cleaner, dip the tip in the thinner in the colour cup, then feed it through (from the rear) the needle passage in the airbrush body shell. Next, feed it through the paint passage of the body shell, starting from the lower end - it will curve and exit from the front of the needle passage - again, pull it through completely. Use a clean rag to wipe off the exterior of the shell, then set it aside. Dip the pipe cleaner into the thinner again, then feed it through the needle support, starting at the front and drawing it through completely. Use it, or a rag, to wipe the rocker assembly if necessary. I keep several cans of lacquer thinner handy, each one for a specific use only. Using the one marked "Cleaner", I dip one end, then the other, of the needle into the can, then wipe it with a clean rag, then use the needle to fish the parts out of the colour cup. These need only to be wiped dry, then the airbrush is re-assembled. The slightly dirty thinner left in the colour cup is dumped into the jar that I use for styrene cement, or into the bottle for cleaning brushes -whichever needs a re-fill.
If you clean the airbrush immediately after painting (I do it even before removing masking tape from any models which I've just painted), you'll never need to spend more than a couple of minutes on this task, and your airbrush will look and perform like new.
Wayne