What's the best masking fluid/paint/substance for tiny, compound curves?

[red4]

I'm planning to spray paint a silver eye plate on a 1/12 scale Mortal Kombat Kano custom action figure. I would brush it on, but I don't want the plate to have brush marks. And I don't want to use a Molotow marker because it never cures. I've heard about Boba Fett helmet makers using toothpaste for the layered paint chipping effect, which potentially means I can use it to mask around Kano's eye plate, but can the toothpaste be precisely manipulated on a tiny area with lots of compound curves, such as a 1/12 scale action figure's face?

Is there another product that can be brushed on as easily as paint, but doesn't bond to plastic, and can be easily rubbed off?

 

[bingoh]

Besides commercial masking fluids, you could try rubber cement.

 

[red4]

Besides commercial masking fluids, you could try rubber cement.

If there's a base layer of acrylic paint, would a product like Liquitex Masking Fluid peel away from the paint, or take the paint with it?

 

[bingoh]

If there's a base layer of acrylic paint, would a product like Liquitex Masking Fluid peel away from the paint, or take the paint with it?

I have minimal experience with masking fluid but I would assume properly-cured acrylic would survive, but better to do a test piece first.

 

[red4]

I started a test with Liquitex Masking Fluid. Since it's designed for the absorbent surfaces of canvases, there was a little bit of trouble making it work on the action figure's smooth PVC head. Initially the masking fluid wasn't bonding, and was sliding around in a hydrophobic way. I noticed 2 distinct thicknesses of fluid displaying 2 distinct behaviors. The fluid that was thick enough to be visibly white was the stuff that rolled around and didn't stick. But the fluid that was applied completely clear stayed where I put it. So I proceeded to apply the thinnest possible layer, which was much easier to control. I also noticed in areas where I repeated brush strokes, the fluid had already dried after about 10 seconds, and was peeling away from the gentle friction of the brush. So I made sure not to apply too many strokes if they weren't necessary. I'm going to let it cure for at least 24 hours before I spray paint with Dupli-Color Bright Silver. After that is the peeling test.

 

[Antsnest]

Regular liquid latex should work fine for this

Something like this Liquid Latex - Brush On / Dipping Latex

 

[Sluis Van Shipyards]

They may have changed the formula, but I would avoid Micro Mark's liquid mask. It's the only one I've used, which was like 20 years ago, but it stuck and wouldn't come off.

 

[Analyzer]

I personally like Vallejo's liquid mask. I find it easier to paint on the Micro Mask since it is not as thick

Regardless of which one, depending on the curve of the surface you might have to do a few different passes between drying as it tends to settle or pull itself in when

 

[red4]

The experiment was ostensibly successful. I'll have to wait 24 hours to be sure.

I used a Punisher head for this experiment (the final head is a different model, but made of the same stuff). I brushed Model Master Acrylic Flat Black around the eye, and filled it in to mark where the eye plate goes. I did not use any primer at any step in the process. Then I brushed Liquitex Masking Fluid around the eye plate, and the entire rest of the head. I let that sit since September 15 because I got sidetracked. However, today I finally sprayed Dupli-Color Ultra Silver, and let it cure for 3 hours. Then I started to peel the latex away. I was able to use my fingernails to scratch the very edge where the latex meets the acrylic paint, and everything has bonded the way I needed it to. The only area where the silver paint peeled away too much was on the front of the cheek, where you can see some of the black acrylic paint exposed. This is because some of the latex got on that area. Aside from that, everything so far looks successful; I just need to apply the latex more precisely next time. Tomorrow at 8am, once the paint has cured for 24 hours, I'm going to do a scratch test to see how well it bonded to the acrylic paint underneath. It was also very difficult to peel the latex away from the tiny, deep contours in the ears, left eye, nose, lips, and hair. So next time I'm going to mask those areas with tape, and only apply an optimized border of latex around the eye plate.

 

[red4]

I can now confirm the results. Without primer, the Dupli-Color Ultra Silver bonded super strongly to the Model Master Acrylic Paint. I also test painted an ABS tube without primer, and it bonded super strong to that too. I also vigorously scraped the edges of the eye plate to finely remove the latex, and the latex area peeled away easily, while the Dupli-Color remained strongly bonded to the acrylic paint. The border of the silver eye plate now looks cleaner than in the pictures from yesterday's update. I also tried scratching the silver paint off of the acrylic paint; I was able to dig my nails deep enough to squish the PVC plastic underneath, but the paint itself refused to come off. So now I can proceed confidently with the final Kano head.