Need advice on painting issue

I've had this issue when I've overthinned the paints. If you're using alcohol to thin with (Tamiya Thinner is alcohol with retarder), the paint is actually drying before it hits the model. Try using less thinner and more pressure.

I use a fluourescent bulb in my spray booth, but the 2 75 watts aren't helping any! Consider switching the bulbs for those (expensive) twisty fluourescent types, they burn much cooler. And last much longer, and save on electricity so the expense is made up in the long run.

The other thing that may be causing this is the venting. While it may seem that the faster the air is evacuated the better, there is a point where it works against you as it causes what little paint does get to the model to dry out too fast.

Bgrigg wrote:

I've had this issue when I've overthinned the paints. If you're using alcohol to thin with (Tamiya Thinner is alcohol with retarder), the paint is actually drying before it hits the model. Try using less thinner and more pressure. I use a fluourescent bulb in my spray booth, but the 2 75 watts aren't helping any! Consider switching the bulbs for those (expensive) twisty fluourescent types, they burn much cooler. And last much longer, and save on electricity so the expense is made up in the long run. The other thing that may be causing this is the venting. While it may seem that the faster the air is evacuated the better, there is a point where it works against you as it causes what little paint does get to the model to dry out too fast.

I very well may be overthinning. I know the 2% milk rule and that's what I try to achieve but lately I've been trying to thin to something that resembles Alcad. I'll change my ratio and see if it helps. Also, I use both MM Acryl thinner and alcohol and they both give me the same results.

I have a couple of the fluoursecent type laying around. I'll try those also. The thing I've found about these is that even though they may be rated the same in wattage as an incandescent they're not as bright. Could be my imagination.

My venting system is actually an old fan ass'y used in a kitchen above the stove/oven for exhaust. It has two fans in the housing, one on each end, and draws VERY well, maybe too much? I'll save this idea for last since it'll be the most difficult to alter.

On a side note and FWIW, I'm not a big fan of Tamiya paints, not out of an a/b anyway. It's never been an issue with color or selection but of how fast it dries. There's a red flag here with my paint issue and I'm beginning to lean toward the "too much heat/air" theory. I'd really like to use some of my Tamiya paints. Maybe if I get this thing under control I'll be able to do that.

Once again, thanks for your comments and ideas. As always, you're a kind help.

Hud

 

I use a kitchen hood as well, on High I'm lucky to get paint to the model. Low works fine for me. I use the high setting when I'm spraying cleaner through the AB.

Flat paints do have a texture, it is the "hills and valleys" that deflect the light from reflecting straight back at your eyes like gloss paint. It should'nt feel like sand paper though.

I've noticed an improvement with less thinner and more pressure. I used to spray at 10-12 and now spray around 18-20, if I can trust my el cheapo regulator!

I know what you mean with the fluourescents not being "as bright" I've painted the interior of my booth gloss white enamel which helps. The fixture I'm using is 25 watt, equivilent to 100 watt incandescent. I find you need at least 3 of the 15 watt (60 watt equivilent) to be bright enough for reading or painting.

Also try an acrylic retarder!

Never thought about reducing the speed of the fan, duh. I do have that option also, maybe I should take advantage of it.

I've replaced the bulbs as I said I would. Much cooler! Hopefully that will help.

I've already experimented today with not using so much thinner and the cooler bulbs. I think I'm on the way back to where I used to be with it, i.e. no problems. Funny how you can go off on tangents, not even meaning to. Oh well, give me enough rope and I'll hang myself . Thanks again.

Hud

Yay! Glad to hear there's an improvement.

It's always a pleasure to assist others.

Cheers!

Bill

One important item that you didn't mention is how far are you from the surface when spraying?  The reason that the paint looks like it is drying in the air is because it probably *IS* partially drying in the air.  Everything Bill mentioned is important, but one key item is time, or more specifically how long the paint is in the air before it hits the surface.  I normally spray using pretty much the same thinning / pressure criteria as you do, and I spray from about 2-3" from the surface..

I'd also strongly recommend adding an acrylic retarder to your mix or try Tamiya thinner (which contains a lot of retarder).  This will significantly slow the drying time of acrylics and make them spray a lot better.

Thanks Scott for your input. I've thought about the distance element and I'm like you, generally shooting from 2-4 in away. Least I try to keep it at that distance. One of the things I've noticed is that the paint , as soon as it hits the surface, dries. Right in front of my eyes, you can see it happening. One thing I have noticed is that this occurence does not happen on the tail surfaces nor down the sides of the fusalage, mostly just on the wing surfaces, i.e. the vertical surfaces are ok, or so they seem. Could that be overspray?

 One thing that both you and Bill have mentioned is the retarder. I think I'll pick some up, when and where I can find it, and give it a go. I'm assuming that I can find this stuff on a mailorder site. Also, will the Tamiya retarder work ok with other acrylic paints? I know I can find the Tamiya brand within a reasonable drive. Like I said earlier today, I've been adjusting this afternoon and I may have things under control ( changing things like bulbs and the flow of venting air) but it's too early to tell. I'll keep trying different things until I get back to "normal"  Hey, why quit when you're losing.   I just wish I'd never deviated from the way I was used to.  Live and learn. Thanks again.

Hud

For acrylic retarder check an arts store, Michaels, Hobby Lobby, that sort of place. It's designed for art acrylics, but works with model acrylics as well. The Tamiya thinner is really just alcohol with retarder built in. DON'T buy the little bottles, it's valued higher than gold! I buy the 250ml bottles, and it is much cheaper. Though Isoprophyl Alcohol and acrylic retarder will be far, far cheaper still. That expense is the big reason I started cutting back on thinner!

I should have mentioned time and distance! Everything I know about airbrushing I learned about on Scott's website... Sigh, the student hasn't surpassed the teacher yet!

I should have mentioned time and distance! Everything I know about airbrushing I learned about on Scott's website... Sigh, the student hasn't surpassed the teacher yet!

Already warned you about that once, Young Jedi   

Brands to look for at art supply stores are Liquitex, Createx, Golden, etc.  I've been using Golden Airbrush Medium lately and really, really like it.  It isn't specifically a retarder but a medium, and really improves the paintability of acrylics ni my opinion.

Hud, seeing the paint dry right before your eyes means that it was nearly dry when it hit (not fully cured, but dry on the surface).  That is the major problem with acrylics is that they just dry to the touch too fast.  Retarder helps a great deal and will most likely solve most of your problems.  It normally only takes a couple of drops.  I did try something once, just to see what would happen.  I thinned the paint with retarder at about 2:1, and it took it about a day to dry to the touch!

There is a very good page on Golden's web site about how acrylics dry and cure.  It is very informative and worth looking at by anyone who paints with acrylics.  Here Is A Link To The Page  Pay special attention to the section entitled "The Two Drying Stages Of Acrylics".

Thanks again! I really appreciate both your's and Bill's advice. I'll definitely pick some retarder up today. Thanks to all. What would I do without this forum.

Hud

Actually, if you have too little paint coming out with the air, it will cause the same issue, giving you an almost flat appearance.  Sometimes, you just need to let more paint through the airbrush.