Problem with Paints

[wilo]

right i am using tamiya acrylics and i have found that sometimes the paint will rub off VERY easy especialliy if i have over painted it with another color Also if i try and mask this it will just pull the color off even if i use tamiya tape). the only parts that seem fine are the engine (that i primed) i know this will be due to the primer but i know that most of you guys dont prime smaller items so how do you stop this happening. (it is happening with thinned paints as well as stright out of the pot)

[MPWR]

Tamiya acrylics can be kind of fragile- especially if they haven't had much time to harden. To improve ahesion on bare plastic before you paint, scuff up the area you'll be painting with fine sandpaper, Scotchbrite, steel wool or the like. This will give the paint some 'tooth' to hold on to. Then, scrub the parts with water and a bit of dishsoap, with an old toothbrush. This will clean off any mold release agent, fingerprint oils, and dust- all things which will interfere with paint adhesion.

Also, you learn to be gentle when masking. Tape can be made less sticky by sticking it down to a (clean!) pane of glass a couple times before applying it to paint. There are also other things that work for masking aside from tape- two of my favorites are wet tissue paper and aluminum foil, used together or separate. That was how I did the exhausts on my F40- I knew the metallics and clears I used would have been too fragile to have tape stuck to them.

And of course you learn to be gentle with painted parts. Glad to hear that the paint is staying on your engine- usually engines are a big problem for me. As soon as i paint them, I know the paint starts rubbing away from edges and corners. Every time I handle it, pick it up ,set it down, do any detailing work, etc. It can be a big problem on engines that I have in progress for months at a time - often just before I install the engine, I go over it with a fine brush and a bit of metallic paint, just to touch up any bare spots.

[wilo]

Originally Posted by MPWR

Tamiya acrylics can be kind of fragile- especially if they haven't had much time to harden. To improve ahesion on bare plastic before you paint, scuff up the area you'll be painting with fine sandpaper, Scotchbrite, steel wool or the like. This will give the paint some 'tooth' to hold on to. Then, scrub the parts with water and a bit of dishsoap, with an old toothbrush. This will clean off any mold release agent, fingerprint oils, and dust- all things which will interfere with paint adhesion.

Also, you learn to be gentle when masking. Tape can be made less sticky by sticking it down to a (clean!) pane of glass a couple times before applying it to paint. There are also other things that work for masking aside from tape- two of my favorites are wet tissue paper and aluminum foil, used together or separate. That was how I did the exhausts on my F40- I knew the metallics and clears I used would have been too fragile to have tape stuck to them.

MPWR you are a mind reader that is the issue i have had when doing the F40 exhaust (using your how to by the way) i will try the scuffing and washing trick when i start on the chassis tonight.
cheers

[gasman03]

almost sounds like your using too much thinner. I've been using Tamiya Acrylics alot recenty and found that the less thinner that is needed to better it goes down. I use about a 3 part paint to 1 part thinner mix.

[bvia]

You can also use a toothbush and scrub the part with Comet (or any other abrasive type cleaner). This will give the part a uniform scuffed surface.

You could also mix the Tamiya acrylic with Mr. Color Thinner instead of the usual (IPA/Tamiya acrylic thinner etc). This will alow the paint to etch into the surface and make the bond more durable...

hth,

[RallyRaider]

Best way to stop that happening to not use acrylics. Laquers and enamels bite into the surface much better. With acrylics surface preparation is crucial as explained above.

[mickbench]

Originally Posted by RallyRaider

Best way to stop that happening to not use acrylics. Laquers and enamels bite into the surface much better. With acrylics surface preparation is crucial as explained above.

True, but enamels don't bite into Lacquers too well. I tend to mix lacquer thinner into enamal when painting enamels over TS sprays etc, this gives them a bit of tooth.

TBH, I've never actually had a problem with Tamiya acylics when sprayed. I thin them to like milk, and apply a few mists, and a couple of finish coats and leave for 24 hours. I'm then done.

Brush painting the stuff however is different. I've had many problems trying to brush paint acrylics. The are best applied by airbrush, reasons I use enamal mixed with lacquer thinner to brush with.

[RallyRaider]

Yeah true enamels don't stick too well over laquers. That's a fact that can be avoided or exploited.