Hey folks - I’ve recently discovered the joy of working with Tamiya’s acrylics in the AB. I guess some folks have problems with them but I have had none so far (knock wood). I’m hoping I continue to be lucky. But I’m wondering how long I should wait before masking a painted surface for camo. I’ve used no primer, I’ll be using Tamiya’s tape too, and I know this paint dries fast but I think it may take a while to cure fully so that it can handle being masked over. Any ideas? I am eager to finish this puppy (the lack of noxious fumes is a real pleasure) but I don’t want to destroy my work so far. Anyone have any horror stories? Thanks [?]
I think most people have problems brushing the paint, not spraying.
I let the paint cure for a minimum of 24 hours. That usually isn’t a problem since I have so many things on the go at the same time that there is always something to work on.
Personally I’d be very reluctant to mask unprimed acrylic at any time. If I have to mask it, it WILL get primed. Give it at least 24 hours to cure (48 would be better, and more even better). Acrylics cure from the outside in, like most paints, and the surface will dry long before the inside cures. Unlike enamel or laquer, acrylics do not adhere well to bare plastic so be very, very careful when removing the masking tape.
As a general rule, always prime. Also, I like to lay a clear coat down between colors, just to “seal the deal” if you know what I mean.
I can personally attest to having problems brush painting the Tamiya Acrylics, however they work beautifully when airbrushed.
Drying time depends on temperature and relative humidity. High humidity slows drying, high temperature speeds it. Dry to touch: paint does not come off on finger or other touching object. Tack-free: the surface is no longer tacky, or slightly sticky, but the paint can be deformed (say by a fingerprint). Soft cure: paint no longer deformable, but not fully cured. Final or hard cure: polymerization essentially complete. Curing time depends primarily on temperature. Cool temperatures generally slow curing, warmer temperatures speed it up. I have had no problem with Tamiya bonding to unprimed plastic, provided the plastic was CLEAN, and the paint was THOROUGHLY cured. That means not less than 24 hours at 68° F, preferably 36 to 48 hours. In fact, I generally use a light gray Tamiya as my primer! Curing can be accelerated using a food dehydrator, which provides gentle heat and air flow. Be sure to wait until the paint is tack-free before putting it in the dehydrator, or you’ll have a paint surface full of dust.
Thanks everyone for the feedback. The initial masking that I had to do was just to prevent overspray onto the pre-painted underside of an aircraft - an 1/48 Hasegawa Hs-129 B3 that (convenientally) has a nicely angled fuselage, so there wasn’t too much masking to do. I waited ~36 hours, and using Tamiya tape (which is nice and lo-tack) I noticed that the painted underside was fragile - had just a little bit of pull-up. Fortunately I’ll be able to touch this up pretty easily. The top of the aircraft is much more complex, so I’m using MM enamels since there will be a few different masking jobs for a winter camo pattern. I guess in the future I’ll always prime with acrylics. I just love how easy they are to work with and clean up. Should I be nervous, however, to do extensive masking on them even if they’ve cured a few days and if they’re on a primed surface? I’d hate to do all that work and then have it wrecked. How about liquid mask products on an acrylic surface? Thanks again [:D] Jon
I’ve never had fully curred Tamiya paint come off the surface with a masking material of any kind. However… I almost always use the dehydrator to “bake” my paint at just under 100° F to 150°F, or let the model sit for about a week…or month…or years…[
] (DON’T USE AN OVEN!)
I’ve occasionally used liquid masks, but I usually avoid them because of my frequently interrupted modeling style—you don’t want to leave them on for a long time. Personally, I prefer to pull off the masks as soon as the paint will tolerate it.
Something else just occurred to me: I never thin Tamiya paints with anything but 90% isopropyl alcohol. That may be a factor in the excellent adhesion I always get. As I recall, Walt Fink told me that, and my (very long ago) paint/thinner compatibility testing indicated that 90% isopropyl was more compatible with Tamiya paints than water. Isopropyl also wets styrene surfaces better than water. The upshot of all this is that the solvent you use for dilution may have a significant effect on paint adhesion.
BTW: If your significant other likes to cook, buy then a good food dehydrator—then you can use it to cure your model finishes. [:O][C=:-)]