tamiya fine surface primer and masking

Eagle hope you are wearing a respirator cuz that MEK is an excellent product but very toxic. 

I know it sounds a little scary, but I've actually been getting really good results with thinning Tamiya grey surface primer with MEK.  I always shoot my Tamiya primer with an airbrush after decanting the primer into a mason jar.  I have a box of 4 ounce mason jars and drilled a hole in one of the lids to accommodate a 1/4" ID rubber grommet.  Then I epoxy a flexible part straw right to the Tamiya spray nozzle and when that's cured, I decant to whole can directly into the mason jar.  Once that is done, you can thin it with MEK to shoot it from the airbrush, and the MEK helps it take a nice, solid bite on the plastic.  As long as that mixture is only airbrushed, the plastic isn't damaged by the etching effect.

Greg

It seems all plastic spoons are not created equally. Some are polystyrene, some are stuff I can't even pronounce.

 

Greg you beat me to it, about to say the same thing about the suspected spoon plastic material.  Tamiya primer or any solvent type primer has never failed me. Also if you use Liquid Mask on a canopy, you must wipe the clear parts with alcohol first otherwise the masking liquid will bead up.

I did a bit of Googling about plastic spoons yesterday whilst musing over this thread. It seems all plastic spoons are not created equally. Some are polystyrene, some are stuff I can't even pronounce.

So maybe you are on to something there.

I checked my current test spoons just a bit ago, to my surprise they both passed the scratch test, both with various layers of acrylics. A layer of Vallejo didn't even scratch off, which has me scratching my head harder than the spoon.

Thanks everyone for your input. As far as sanding and cleaning beforehand, I am also doing all of that. It might very well be the spoon itself. never occurred to me the plastic might not be a good platform. now it seems obvious! not all plastic is the same. I have actually had seemongly good success in the past with a box of spoons from the grocery store. This time around I was using ones from various takeout food orders, and they are indeed flimsy-so probably not good for testing. 

Just kicking an idea around, I know the old habit of thoroughly washing and rinsing the sprues when opening the kit is not often done now, but I have stuck with it for many years. Every so often I find a light, oily film on some parts. That is just contamination, even if it doesn't look like much, and can/will lead to poor paint adhesion and lifting.

When assembly, filling and sanding is completed, I lightly go over the surface with alcohol and lint free pads. Then, prior to priming I use a light foam scuff pad, about 800-1000 grit, and go around all of the surfaces I can reach. That provides enough surface disruption, that I get a sufficient "bite" for the primer to attach firmly to.  Light alcohol wipe again, that's the last one.

After priming and before finish paint coats I use a clean 800 grit pad, to again assure sufficient paint adhesion to the primer. I don't mean this as an "only way" to finish models, just my suggestion as a way that has worked really well for me. I don't for sure know how long it's been since I had paint lift, either enamel or acrylic, but it has been a very long time.

I would guess I invest no more than an extra hour total, over the course of a build. Maybe someone else will find this helpful.

Patrick 

hypertex

Could be the spoon.

I was wondering that, too. In my experience, Tamiya Fine has been pretty much bulletproof.

Do you use spoons for adhesion tests regularly? I've never thought to even try it, I just use them for color tests, to make sure I have a consistent spray from my a/b, etc. Reason I ask is I guess I didn't know if our paints are to be expected to stick to our test spoons.

I'm not suggesting you are doing anything wrong, I'm just curious.

I'e never had that problem with Tamiya Fine, either. Sounds like you have an adhesion problem, not a toughness issue.

Could be the spoon. The spoons I have are solvent resistant. Don't know what plastic they are made of, but it's not styrene. If yours are too, that could be why the lacquer isn't sticking. Try applying Tamiya Extra Thin cement to a spare spoon. If the plastic doesn't melt or etch, then it's not styrene; and that is probably the reason the lacquer isn't sticking.

You could also try scuffing the spoon with some fine sandpaper, might give it some tooth. Smooth plastic does not hold on to paint very well, especially if it's not styrene.

I'm being conservative on alcohol these days, still not in stock around these parts. I have a quart of 70% here and about 2/3 of a pint of 91% left. And mineral spirits always worked well anyway.

"I have never had that problem with the Tamiya primer,  but I also clean surface with isopropyl or thinner to clean it, then let it dry thoroughly."

oldermodelguy

Could have had some oil on there from your hands on the second one. But that said I've had no issues with stynylrez myself and pretty much have just been using that for going on 2-1/2 years now. So it's been a while since using solvent based primers. I tend to pre wipe the bigger parts with either some alcohol or mineral spirits, usually the latter. All my test subjects get wiped down to have an equal starting point.

 

I have never had that problem with the Tamiya primer,  but I also clean surface with isopropyl or thinner to clean it, then let it dry thoroughly.

Could have had some oil on there from your hands on the second one. But that said I've had no issues with stynylrez myself and pretty much have just been using that for going on 2-1/2 years now. So it's been a while since using solvent based primers. I tend to pre wipe the bigger parts with either some alcohol or mineral spirits, usually the latter. All my test subjects get wiped down to have an equal starting point.