My experience has been fairly good, using old-school beige masking tape, Scotch “Magic” (flat) transparent tape, 3M blue tape, or the light green 3M high stick tape. I prefer the 3M blue product. Scotch “Magic” tape can do really sharp lines on flat, smooth, surfaces, but it has no ‘stretch’. It won’t go around complex curves, stretch to fill engraved lines, etc. It can be hard to remove too, if you don’t leave an edge up somewhere.
First you need the base glossy paint to be well attached. Clean all the parts on their trees with Luke warm water and dish detergent, hand soap, light scrubbing with a green dish scrubber, light sanding with 600 or finer wet-dry sand paper, your choice. Do what’s worked for you in the past. Lay the paint down lightly and evenly. Keep the model parts warm enough before and after applying paint. Keep the paint warm too.
Having a gloss finish doesn’t require glossy paint. Future floor wax, gloss finish lacquers, gloss acrylic, gloss enamel, what ever’s right, after all the paint colors are in place, gives the thinnest finish.
If you’ve already got the glossy paint down and you’re wondering how to mask over it, there’s still plenty of little details to attend to.
Roughing the area the second color will go on doesn’t hurt- my problem masking is as much about the second coat not sticking on up to the masking line as it is about the first coat pulling off or separating.
Having a clean, fresh, edge with effective adhesive is VERY important. You can get along with the edges of the roll of tape as it comes from the maker IF its fresh and you just unwrapped or opened it. If the roll is a long term resident on your workbench, or the sides/edges are scruffy, its not going to make a clean, tight, line.
I keep my masking tape in a small zip-log bag now, stand it on its ‘tread’ instead of laying it on its ‘sidewall’, in or out of the bag. When I want a really crisp edge, I take a nice length of tape and my sharpest Fiskar scissors and cut the tape, straight, down the middle- this gives two, straight, sharp, edges. If I need a line longer than the length the Fiskar’s blades, I piece it from several pieces of tape, to make the edge, and fill with a second layer. I don’t overlap the joints, I trim the edges to slightly less than 90 degrees and lay the pieces down point-to-point, starting like:
1st color layer…
area for 2nd color.
Smallish filler pieces to cover the little triangular gaps are good. In general I find that small, narrow, pieces of tape are easier to use over curves (or to make curves!) than wide tape. I usually buy 1″ (25mm) and often cut it in half or thirds or quarters before I apply it. Getting a crisp edge is NOT the same as covering a large area- mark out the edges with narrow strips, then use full-width strips (or paper or plastic) to cover bulk areas. Yes, its hard to get long, straight, lines with narrower strips. Its hard to get long straight lines with big, wide, pieces too. Once its stretched out of shape, you’re better off throwing it away, or cutting it to the straight edge you need. Piecing out a long line in scissors-length pieces against a metal straight edge is possibly easier than applying a 2 foot (60cm) piece of tape…
Once the tape is down, burnish the edge, and any seams. Something smooth. slightly soft and gently curved like a Bic pen cap, orangewood stick, etc, is good. Fingertips work.
If you’re worried about stuff running under the tape (via deeply engraved panel lines, rough surface, whatever) dust a light coat of the base color or a clear to seal the edge of the tape. EASY does it, no blobs. Just enough to seal.
Now lay the second color down, in light, thin coats. More tape and a third color, etc, can follow. Using flat paint and not having to sand-down gloss finish for subsequent coats to stick to is clearly an advantage….
Some people like to lay a thick, wet, coat down and then lift off the masking as soon as the second color will stay in place… Ummm, that isn’t easy to do in thin, light, coats… Slicing along the tape edge with a brand-new knife blade is good, if you’re making a ‘straight’ line, a straight edge to slice along may help. Slice LIGHTLY, don’t go through the 1st color, or down into the base material of the model.
PEEL the tape, gently, slowly, pull AWAY from the masked edge. Peeling off the tape is a big part of getting a good masked edge. But like all human activities, it isn’t really true that there’s one and only chance, or that it can’t be fixed if there are problems. Personally, if I think any of the paint might still be wet (uncured) I shelve it and come back in a day or two.
But don’t heat something with masking tape on it, or leave it on the dashboard of the car on a summer day… Overheated tape stickum is a complete BEAR to remove. Ask me how I know…. After a year or two, the old, beige tape, stickum would vulcanize or cure or whatever you call it- become stiff and hard and require sandpaper to remove. The new, gentler, “blue” tapes are far more forgiving.
After the tape is off, there may be a ridge where a taped line was. Fine or extra fine fingernail sanding sticks, wet, are good for working down the ridge without losing the sharp edge. The stiff sanding stick is easier to control than a floppy sheet of sandpaper, and you only want to affect the stuff that’s sticking up.
Another reason to paint flat paint and gloss it later.
For natural metal finish with solid colors as well, I cover everything that will be bare metal and do the paint first, completely, including masking-ridge-sanding and the gloss coat, then tape off ALL the paint and spray Testor’s Metalizer (from rattle cans) over the bare plastic. So everything gets masked once, at least. (The airbrush-able Metalizer works just as well, and you can mix it and tint it, but I choose to use my time on other things.)
NEVER try to save materials when masking. Use fresh tape, use more tape, remove the tape and start over if you don’t like what you see. The tape is cheap, your time is expensive.
That said, don’t make your life harder than it needs to be. If you’re painting the tips of wings and rudder, mask the EDGES of the tips off, then cut some slits in a paper bag, and use the bag to cover all the model, except for the little bits you want to paint. Its not saving stuff, just making your life easier. Wrapping something completely in tape isn’t much fun, and risks overspray on gaps that require a lot of inspection to check.
Well, that went on too long, but you’ll have a good time doing multicolor paint and paint + natural metal. You can do the gray wings with polished leading edges, flat aluminum panels, satin finish engine intakes and maybe a titanium bit on the engine pylon.
Take a shot, take some pictures, let us know how it goes for you!