Splattering Tamiya Acrylics

Thanks everyone for the responses.

Triarius: 

it's fairly cool at the moment, no idea of humidity, but would assume low.

Scrambler8:

not sure what you mean by .5-1 cfm.  you're right that it's a siphon feed, and the nozzle is variable.  have played with this and can get excellent results with Gunze paints (which i thin 2:1) using the same set up (brush nozzle, compressor etc) doing freehand camo, but just seems to be these tamiya's that splatter.

i think it might be i'm not thinning enough - most of you seem to suggest 1:1 or even more thinner to paint.

i'll put my experimenting hat on again and see how i go.

thanks for the tips.

cml

I tend to go very thin with Tamiya acrylics and build up the required colour depth in multiple thin layers. 

I often use methylated spirits to thin flat colours. I've found that you can push the paint further with methylated spirits (eg. 4:1 thinner:paint) than you can using Tamiya thinner without the paint beading and failing to adhere. It seems to have better "wetting" properties than Tamiya thinner. 

However, gloss colours work better with Tamiya thinner, whereas they don't rseem to retain their gloss well when you use methylated spirits as an alternative thinner. For gloss colours I use Tamiya thinner.

Airbrushing Tamiya metallics can be quite tricky. Not enough thinner and it won't flow - too much and the metallic particles settle too quickly and (a) clog your brush and/or (b) you get a colour shift because the particles aren't distributed evenly through the carrier, which can contain different coloured pigments. Work quickly before it settles in your paint jar/cup. Actually, I've found Tamiya chrome silver is one of the easier colours to airbrush because it doesn't contain any other coloured pigments in the carrier. Try thinning it a bit more, perhaps 2 parts thinner to 1 part paint, and see how you go. 

I ust Tamiya paints about 80% and Model Master the other 20%. I have good luck with the Tamiya paints.

I thin the paint approx. 50/50, using Tamiya thinner. I say approx., because I don't use a specific measuring device. For me, splattering happens when I'm trying to spray with a higher pressure and too close to the model. My AB's have pre-sets for the triggers that allow me to limit the maximum amount of paint coming out. I also turn down the air pressure to 7-10 psi when I'm doing close up work or camo painting.  I 've found that this limits splatter. IMO, the closer you get to the model, the more coats of paint you'll have to apply. My first coat on a camo scheme is almost hard to see. However, by the time I've applied the 3rd coat, there is a nice covering of paint.

For general paint application I use a brush with either a .30 mm or .40 mm needle. For close up and detail work, I use either a .15 or .21. I should also state that all of my AB's are gravity feed. I haven't used a siphon feed in quite a long time. A siphon feed will generally require a higher pressure to draw the paint out which could be contributing to your problem.

You state that you use a Paasche #1 (is this the H#1 single?). If so, you're using a single action, external mix brush. the specs list the spray pattern at 1/32 to 1". It needs .5 to 1 cfm, and a psi of 20-45. Here's what I think... With a siphon feed needing that kind of psi, you've got too much pressure when you're near the work piece and splatter is going to happen. When you try to turn the pressure down, due to the siphon feed, you're getting inconsistent paint flow that results in a splattering effect, as the AB need more pressure to pull a proper amout of paint out and to the nozzle. That model of AB is currently sold with a .45 mm needle. Depending on the kind of effects you are aiming for, that could be too big.

While I'm sure there are people using large needle, single action, external mix brushes that get great results. For me, and my skills, it would never happen. I would use such a brush to lay down a base color. For close in detail work, I'd go with a double action, gravity feed, smaller sized needle/nozzle combo.

After all that, I guess I should ask what type of painting you're doing that is resulting in the splattering? If you are having the problem putting down your base color, then have you made sure the brush is completely clean and the needle and nozzle are free of paint build-up? Does your brush have a separate control (at the back of the AB) that allows you to limit paint flow? if so, have you played with that variable? If you are trying to do close up, detail work, then I think you'll have to start using another kind of AB. My memory of the H#1 is that the paint volume control is under a removeable plastic cover on the back half of the brush. Try that, limiting the paint flow - and using more coats - to see if you can minimize the splatter.

Finally, what kind of compressor are you using? Is there an air tank that eliminates pulsing? If not, the paint splatter could be the result of that pulsing. Lots of variables.  

Slightly greater than 1:1 (more thinner to less paint) might be closer to the mark. The consistency of 2% milk is what you want. Viscosity is critical with Tamiya paints.

About 12 to 18 psi, higher for gloss paints. You need to balance viscosity and pressure. If your viscosity is high (low solvent) your pressure needs to be a little higher. if your viscosity is low, lower pressures are better.

What is your relative humidity and temperature? Tamiya thinner is essentially isopropyl alcohol and a retarder—high temperature and low humidity can play havoc. If your relative humidity is low,or your temperature above~70°F, try increasing the amount of retarder or adding a little water as a cosolvent.

As aerosols, Tamiya metallic acrylics are…over-rated. Not bad brushed, but sprayed……they are problematic.