WIsh I had read this somewhere before I decided to put my Tamiya Spitfire Mk.Ia in my curing oven with masking tape on it.
I went to remove the masking from the lower surfaces this afternoon, and was horrified by what I had found. I used my handy-dandy home-made curing oven to help cure the paint between successive layers, and apparently you cannot put a model in there with any kind of masking on it. The curing temps (which I use on other models with excellent results) appears to have softened up the adhesive on the tape (Tamiya yellow tape) and softened the paint itself and fused them together. The bottom on the plane has an awful smeared look to it, and will have to be completely stripped down and redone. Perhaps this is common knowledge, but it never occured to me! But on the bright side, I get more practice painting! For those who don’t know me, I have stripped and redone several aircraft in the last couple of years, so I am getting pretty good at it. The last one (my Zero) turned out even better the second time around so I guess it was worth it (in a sick sort of way!). I am going to put her aside for a bit, and pick it up again in a month or two. I’ll post WIP pics of the restoration then. I thought I would share this in the hopes it saves someone else from repeating my mistakes.
What kind of paint? What temp is your “oven” at. Heat isn’t what cures paint…lack of humidity is. Room temp 70-90 degrees is sufficient but much more than that can keep the paint sticky and soften the tape if left for prolonged periods of time.
Quite a few years back a friend of mine use to make jerky. He’d prepare his meat and have it ready to dry. He’d hang the meat on a rack that had stainless steel rods. After he had the rack loaded up, he’d set it on top of his garden shed roof. The roof caught the sun pretty much all day. Over that rack he placed a frame covered with fine screening. This screening kept out the bugs and dust.
I made a similar one using the same material. I could set my model outdoors in a spot that was protected from direct sunlight but was not totally shaded. The screening on the cover kept the bugs and dust off my model. Regardless of the paint I used it would cure in a day because of the low humidity and breeze of the Montana air. The parts never got above ambient air temp so the paint never stayed sticky from heat. Never had a problem with masking tape softenin either.
I suggest you turn on the oven to warm it up, set the model inside for say…fifteen minutes then turn the oven off and leave it sit overnight. The initial heat will start the drying reaction, and shutting it off will curb the softening yet allowing it to still dry. If your oven is in a damp Wisconsin basement…move it to a drier environment such as a bedroom or closet.
What I think you meant to say is that very high humidity can delay paint curing, which it can, regardless of the paint system. For acrylics, the reason is obvious, although the actual chemistry can be fairly complex. For enamels and lacquers, it has to do with surface chemistry—the partially dried and cured paint surface develops an odd affinity for water molecules.
Heat very much does cure paint, because curing is a chemical reaction and is accelerated by heat. However, if the paint solvent—regardless of what the solvent is—is trapped or inhibited from leaving the vicinity of the paint surface, it will continue to inhibit cure. Air circulation is an absolute necessity.
To much heat will soften almost any fully cured paint. Curing temperatures for hobby paints should never be much more than about 110°F. Anything much highwe and you are asking for trouble.
Heat, even relatively low heat, will also soften many of the adhesives on tapes commonly used for masking. Because they are polymers, too, they may do some cross-linking with the polymer in the paint, causing goo.
Ross you going to be at the meeting tomorrow night? Al and I are doing SnJ & Talon demos! Wonder how high it will have to go before meetings are cancelled because no one can afford to drive to the meeting. For guys like us who have the l o n g commute it might be sooner than we think.[:(]
Barring incident, I plan to be there. Looking forward to it!
Fortunately, being retired, I don’t have to commute every day. It still infuriates me that the oil companies are making obscene profits never seen before—and they’re making them off us.
LOL, sorry to chuckle about your troubles Daywalker but when I saw the headline and read your report I couldn’t help it. I’ve never heard of curing a model job in an oven but it would seem axiomatic not to have anything on the paint because hardening and “fusing” coatings is precisely the point, no? And have you never seen tape that’s been exposed to the sun for awhile? There’s another word that comes to mind when reading your story that may help clarify things in the future- BAKING.
Thank you fellas. I do run the oven up to 100 to 110 degrees for an hour or so, in a climate controlled (mostly!) basement. The humidity is 60-65%, temp around 68-72 degrees. I used Gunze paints, letting them cure naturally for three days before baking them. I am going to try your suggestions the next time around. Guess I really should have thought about it more before doing it, but past experience has shown that the most valuable lessons are the ones learned the hard way. I WILL be more careful in the Future! Thanks again for your help, much appreciated! [tup]
I would agree, mask and spray an area and then remove the tape while it cures in the “curing oven” and then go back to masking if need be and paint again. Masking tape should never be left on after the paint has surface cured anyhow and if you are using flat military colors that means masking tape can be removed almost immediately after spraying.
