Airbrush issues with Mr. Hobby paint

[Jim Kiker]

Hi all,

I am doing some painting of subassemblies and having a problem. I am learning how to use Mr. Hobby (solvent) paints. I use only the Mr. Leveling Thinner. The paint is very thick from the bottle, so I have started putting thinner in my airbrush cup, up to about half full, then adding drops of the paint until it begins looking like tinted thinner or skim milk in consistency. I run the airbrush at 20 psi for this paint with a .020" needle and tip (my normal equipment with a little more pressure than other solvent based paints). I normally work fairly close to the surface being painted; the problem is, I am getting spider webbing and a gradual build-up of paint on the airbrush tip, with some spitting as well. I cannot seem to get the thinning right.

Any ideas on where I'm going wrong?

Thanks, Jim

P.S. At least this is for an airplane project! :-)

Edited February 5, 2015 by Jim Kiker

[acting_strange]

If you are getting spider webbijng then your paint is too thin/ or your pressure could be too high try moving your brush further away.....why do you use solvent paints?.....acrylics are much more user friendly?

[Jim Kiker]

Hi A S,

I have been using solvent paints for a long time, and I like them because they stick well on plastic. My limited experience with acrylics is that most of them perform best after using a coat or two of primer, which in my experience tends to cover up fine detail rather quickly. In the end, it is a matter of preference I suppose. Meantime, maybe I've got the mix too thin. Thanks for the input!

Cheers, Jim

[Seawinder]

Jim, are you sure it's Mr. Hobby paints you're using? If so, I believe those are aqueous acrylics, so it's quite possible the thinner you're using is incompatible. If you're using Mr. Color acrylic lacquers (solvent based), in my experience spider-webbing is virtually always the result of the paint being too thick. The Mr. Color paints can be thinned quite a bit (more than other brands) and still should cover acceptably.

Cheers,

Pip

[JackG]

I've seen it stated that you can still use the airbrush while removing the protective nozzle at the end. That should eliminate paint build up and the spitting in the interim while figuring out what else is going on.

regards,

Jack

edit - Just did some reading, and it appears Seawinder might have uncovered the problem. Mr.Hobby Color is a true acrylic paint, while Mr.Colour is the Lacquer-based paint.

Edited February 5, 2015 by JackG

[Chuck1945]

If you are talking about the GSI paints, Mr Hobby are the aqueous colors, Mr Color are the solvent versions.

At least in my experience, paints as heavily thinned as you are describing (just tinted thinner) and used close to the surface are best applied at less than 10psi.

[Jim Kiker]

Hi Pip,

I may have confused the names, but this is the solvent version of the Gunze line. Here in the U.S., the aqeous line is very hard to get if at all. The solvent paints can be ordered on-line.

When I first started to paint last night, I thinned the paint similarly to other solvents so it would have been not thin enough. When I switched to a much thinner mix, I did not stop to thoroughly clean the airbrush tip, so that may have had an impact. I did run straight lacquer thinner through the airbrush, as usual, but it may not have cleared the tip completely.

And for Jack, I use a tip protector made by the manufacturer that is more open than the one the airbrush is sold with. What I did see was a thick build-up on the end of the needle when I started painting.

Thanks gents, Jim

[Seawinder]

Hi Jim.

I'm in the USA also. So it appears you are indeed using the Mr. Color paints. Upon further reflection, what I described as spider-webbing when the paint is too thick is actually closer to what I'd call the cotton candy effect -- spidery strands in the air that appear at the far edges of what's being painted. If that's what you're describing, then definitely thin the paint more. However, if you're talking about spidery splatters on the surface, then perhaps either the paint's too thin or you're applying it with too much pressure. FWIW, I generally go with 16 psi working pressure.

[Jim Kiker]

Hi Seawinder,

You are correct in your description of spidering- cotton candy strings around the edges of what I'm painting. Funny, I should have recognized I had too much pressure, but I bumped it up while encountering the spidering and didn't take it back down after more thinning. One thing I do find is that it's much easier for me to thin the paint in a mixing bottle for airbrushing than mixing it in the cup. When I get the thinning right, I can spray at 12-14 psi and get fine results. Thanks for the input!

Cheers, Jim

[Dave Fleming]

How to deal with them? Have a look at at about 38 minutes in this video:

Actually have a look earlier as he explains why and what thinner to use.

[Seawinder]

Hi Seawinder,

You are correct in your description of spidering- cotton candy strings around the edges of what I'm painting. Funny, I should have recognized I had too much pressure, but I bumped it up while encountering the spidering and didn't take it back down after more thinning. One thing I do find is that it's much easier for me to thin the paint in a mixing bottle for airbrushing than mixing it in the cup. When I get the thinning right, I can spray at 12-14 psi and get fine results. Thanks for the input!

Cheers, Jim

Yes, I was going to suggest that. Much easier to get a good working solution in a bottle and decant it into the paint cup as needed.

[Rizzo]

Mr Leveling thinner works just fine with either the Mr Hobby Aqueous paints, or the Mr Color paints. And they both spray in exactly the same way as far as I can tell (if anything, Mr Color is more user friendly). The only difference is the Mr Color stuff dries to a much tougher finish.

I've found it best mixing with 2:1 thinner to paint, and turning the paint flow way down, so you just get a very fine mist. Then get a decent layer down by going over the same area several times, instead of one thick layer in one or two passes.

Edited February 5, 2015 by Rizzo

[DominikS]

With GSI paints (both H and C) I only use "yellow" Levelling Thinner. I have been painting with them since I started using airbrush ca. 8 years ago. I always make a mixture (paint - thinner) 1:1 or 1:2. And the pressure I use is around 1.5 Bar. I think the pressure you use is too high.

[Jim Kiker]

Hi all,

Just thought I'd let you know, I've put all the good advice to work. I poured some of the paint into a mixing bottle, added the leveling thinner to get the consistency of skim milk, and shot it at 14 psi. Perfect!

Many thanks, Jim