Testors over Tamiya?

Sealing over acrylics is not the answer to poor adhesion. A clean plastic surface is.

Learn to get the surface clean before you paint. When you apply a "sealer" over an acrylic, you add nothing to the strength of the bond between the acrylic and the underlying surface.

Tamiya acrylics have superior adhesion when properly applied to a clean surface. I've never had them come off.  I've used them to camouflage my hunting bow, and they are still there, in spite of brush, trees, rocks, weather, sweat, and blood.

On the other hand, on occasion I have found that when masking over airbrushed Tamiya metallic acrylics,  it can lift partially when you remove the tape. A clear coat can help to stabilise this.

Otherwise, if your base coat has had sufficient curing time, it should be just about bulletproof. The only other precaution that I suggest is that if brush painting over airbrushed Tamiya acrylic base coat with other Tamiya colours, tread lightly to reduce the risk of "burn through".

Phil, the problem with metallics isn't limited to acrylics—it can happen with any metallic. Metallics are particularly susceptible to dusting because of the platy nature of the pigment. This also makes them weaker parallel to the surface, and can lead to adhesion problems as well if not properly mixed, or if the formulation is off (due to age if nothing else). Metallics are just more finicky than other paints.

The only metallics I've ever used that seemed to be immune are an acrylic and a lacquer. The acrylic is Hawkeye's Talon, the lacquer is Alclad.

Using a clear coat over the top to prevent the problem is not so much sealing as it is adding binder to a layer of poorly held pigment.

Thanks Phil, appreciate the straight forward answer. Yeah, I let the parts cure for a week. It's been a tad bit humid here lately, so I let it sit longer just in case. 

Triarius

Phil, the problem with metallics isn't limited to acrylics—it can happen with any metallic. Metallics are particularly susceptible to dusting because of the platy nature of the pigment. This also makes them weaker parallel to the surface, and can lead to adhesion problems as well if not properly mixed, or if the formulation is off (due to age if nothing else). Metallics are just more finicky than other paints.

The only metallics I've ever used that seemed to be immune are an acrylic and a lacquer. The acrylic is Hawkeye's Talon, the lacquer is Alclad.

Using a clear coat over the top to prevent the problem is not so much sealing as it is adding binder to a layer of poorly held pigment.

And sometimes it's a question of planetary alignment. Some days it will work out, sometimes not.

Seriously though, I think my airbrush (0.35mm)  is near the limit at which one can successfully airbrush Tamiya metallics. The metalllic pigments in Tamiya paint are relatively coarse and correct thinning is essential. Not enough and it won't go through. Too much and the metallic particles settle out quickly in the cup and cause blockages. This can exacerbate the separation of the pigment  and binder so adding a clear coat can help the situation but it can sometimes alter the appearance of the finish.

Alclad is hideously expensive here (about $14.00 - $15.00 (AUD) a bottle) but it may be worth investigating.

Re Alclad- maybe it's just my fault, but I have never had good results with it.  I have wasted a lot of money on that stuff, and thrown out what I had left.

Phil_H

 

Alclad is hideously expensive here (about $14.00 - $15.00 (AUD) a bottle) but it may be worth investigating.

Phil,

I've had really good results using Alclad, but, as with any metallic, surface prep is everything. It looks more like metal than a lot of other paints. Plastic should be primed because the lacquer may craze the plastic. The advantage is the primer will eliminate fine surface blemishes so you may not need to polish the plastic like you do with Metalizer. I've used the polished aluminum over Tamiya TS-14 gloss black resulting in a terrific shine.

You can see more of this model and using Alclad in the upcoming How to Paint and Weather Scale Models 2.

Cheers, Aaron

Thanks Aaron. That finish is gorgeous.

Phil_H

Thanks Aaron. That finish is gorgeous.

Thanks Phil.