Thinning Paint for Airbrushing

[dave_t]

I have had terrible experiences trying to hand paint Tamiya acrylics, so I avoid it now.

I thin Tamiya colors down for airbrushing, something like 50% paint and 50% isopropyl (rubbing) alcohol and I've also tried PollyS thinner which is also alcohol based. Both work fine. I've had success with Folk Art paints (found in craft stores) and artist's acrylics from tubes, both thinned with alcohol. I've never tried them with water, that may work too.

The Tamiya gloss white looks terrific Garet. I've never tried their glossy colors before.

[Oceaneer99]

Lou,

Yes, you are correct that water is the correct thinner for the Elmer's wood putty, which is a latex-based product.  I have colored similar putties in the past with acrylic paint, specifically, lightweight spackle, which I tinted to look like balsa for lightweight filler in flying models.

I used to brush with enamel, but have almost never airbrushed it.  I switched to (at the time) Polly-S acrylics when I got my first (toy) airbrush.

Dave,

Yes, I agree with not hand-brush Tamiya.  I also ended up with a 50-50% dilution for the airbrush in the end.  I had a small bottle of Tamiya thinner, but it is mostly alcohol.  My Tamiya colors were all from one bag of jars that I picked up at a thrift store a while back.  I did buy a larger bottle of thinner recently, but haven't had to use it yet.  However, I'm now almost out of white, which I'll need to replace to paint my Ascender spaceplane.

I have never tried thinning craft paints with alcohol, though I did learn that thinning with water doesn't work well (the pigment doesn't remain evenly suspended).  I've been using an artist's acrylic medium (I'll have to check the exact name) for thinning -- it looks sort of milky like very thin Future.  Many of my spot colors (i.e., not the main aircraft colors) are Delta Ceramcoat craft paints, thinned down with the acrylic medium.  My submarine models, PT-10, and my canopies were all thinned Delta paint.

Garet

[Ken Pugh]

Lately I have been using a reducer recipe I got from the Airbrush Tricks website.

http://airbrushtricks.com

1 cup water (I use distilled water)
1/2 cup rubbing alcohol
1/4 cup ammonia glass cleaner (getting hard to find, though Windex still uses ammonia)
5 drops glycerine (find it at the drug store/chemist)

Mix it up and put it in a spray bottle.  Works great with all the craft paints I own and makes it so they spray nicely.  I have been using craft paints exclusively.  They are so available I figured I would keep messing with them until I got them to work.

I have found that some craft paints are transparent without telling you, which can be a pain.  Delta Ceramcoat always says whether it is opaque or transparent right on the bottle.  When brush painting the craft paints can start drying very quickly, but this reducer seems to slow it down just a little.  I would guess this reducer will work with most acylic paints, though I'm not sure about Tamiya, that stuff is tricky to work with.

Ken Pugh

[Oceaneer99]

Ken,

Thank you for that reference and formula!

For hand-brushing, I've been using Golden Acrylic Flow Release, which is apparently 30% Octylphenoxypolyehtoxyethanol.  No, that doesn't tell me much, though I read it's some sort of surfactant (breaks surface tension).  

Golden also has an airbrush medium.  I'm not sure what I read to convince me to try the flow release instead.  But it may be time for some more experiments in the SMM testing kitchen, especially with the air brush/

I agree about the transparent versus opaque issue.  Delta's standard white is transparent, so I usually use their Magnolia White (opaque) instead if I'm using craft paint (some of my profile models).

Oh, I did notice that one web site referred to Tamiya as "acrylic lacquer".

Garet

[Ken Pugh]

To the best of my understanding, the glycerine in the formula lowers surface tension of the paint and enhances flow.  Like I said, I have had great results with it so far.  The architectural model I built earlier this year was sprayed with craft paints using this reducer and it worked great.  I mix my paints in baby food containers and pour into the paint cup then spray away.  I was surprised how well I liked using the spray bottle to dispense the reducer.

The AirbrushTricks site has a lot of great stuff on airbrushing.  The guy gives away every secret he has and gets many other big names in the business to contribute.  His forum is also good and he is always there ready to jump in the conversation.  The focus is not on model work but it is still educational for the modeler.  He has really good advice on equipment and how to keep costs down.

Ken Pugh

[Oceaneer99]

Copied from a discussion in Oceaneer99's project board (sorry it's out of order with the rest of the discussion):

Here is the model after airbrushing Tamiya gloss white on the upper surfaces.  There is some overspray onto the winglets, which is why they look mottled:


http://smm.solidmodelmemories.net/Gallery/displayimage.php?pos=-3325

As I suspected, the Tamiya acrylics are really better suited for spraying than brushing.  My first attempt did not go well, however.  I pumped my tank up to 90 psi and regulated the pressure down to 25 psi, but couldn't get the paint to come out, so I increased pressure to 30 psi.  In hindsight, I hadn't thinned the paint enough, so I ended up spraying at the too-high pressure and making a rough, orange-peel surface.  I sanded this flat using a very fine sanding sponge and then tried again with more thinner.  This time, I sprayed at 25 psi, and things went fairly well.

The air tank is my modified fire extinguisher, which is about 3 gallons volume.  Since I wasted so much air the first time, after painting the VKA-23 and the engines from my Ascender spaceplane, the tank was down to about 30 psi, and I had to pump it up again to clean the airbrush.  The second time around, I pumped the tank only to 80 psi (bicycle pump, 0-60 psi is easy; it gets harder and harder after that), and had plenty of air for the painting and cleaning.  Cleanup was faster than I expected, so I'll probably do more airbrushing in the future.  My old (toy) Badger airbrush sprayed almost like a rattle-can, so it took me a few minutes to realize that this one (single-action Paasche) builds up slowly and needs to be held closer to the surface and moved more slowly, but could be used to spray fairly fine lines, such as soft camouflage edges (I was using the large #5 spray tip).

I used a sheet of folded cardboard as my "spray booth", with a desk lamp for extra light.  The Tamiya has a lot of alcohol in it, so that was the only objectionable odor.  I need to make an airbrush holder, since every time I put it down, it wanted to slide off the workbench, pulled by the air hose.

When I was trying to find the book I have that has airbrush problem symptoms (I never did find it; I had forgotten that it is a model railroad book), I did find my references on hand brushing.  One article mentioned that certain flat paints are very forgiving of hand brushing, and I would certainly agree.  I have never had problems hand brushing Testors Model Master Acryl II paint, but the gloss Tamiya acrylic didn't work very well that way.  On the other hand, it makes for a beautiful gloss finish when airbrushed.

Some of my models have a gloss finish, even with the Model Master paints.  I rub the last coat down with super fine sandpaper and then give it several coats of Future.  I painted my pink Spitfire that way.

Garet

[Oceaneer99]

I masked the white portions of the VKA-23 and painted the control surfaces with Tamiya Orange, thinned 50-50 with Tamiya thinner.  I really had to turn down the air pressure this time (15 psi), as I must have made the orange thinner than the white paint.  It's slightly transparent, so I'll need a second coat where the orange went down over gray primer.  I didn't realize how fast the paint was going down when the pressure was higher (20 psi), and ended up with some drips, but there was so much thinner that it all dried flat (whew!).

The air tank went from 80 psi initial to 60 psi after cleanup.  It takes about five minutes to pump it up from zero with the manual tire pump, but goes faster if I already have 20 psi in the tank.  It's fairly cool in the basement at the moment, so the pumping does get the blood moving a bit before I paint. 

I bought some Wagner Paint Easy ($9 for 32 oz), which is mostly propylene glycol, similar to what is used in Golden Airbrush Medium ($9-10 for 8 oz at art supply stores), though I know Golden also uses some ammonia.  I'll try this out for thinning the craft paints for airbrushing.  Paint Easy is sold for mixing with latex house paints for putting them into air sprayers.

By the way, I had some cheap brand of craft paint that globbed when I used ammonia in the thinner mix (Delta paints were fine with it), so the recipes might depend on the paint brand.

Garet

[R.F.Bennett]

Keep in mind that thinning paint will often make it dry faster too. This can be a good thing but if it dries too fast it can leave a "dusty" look to your paint. As Garet has found, the thinner the paint the lower the pressure needed. This can be good when you don't want to blow paint all over your workspace. A few "clear" coats will often provide a better more controllable finish than one or two thick coats. Also, your paint mix will behave differently depending on room temp and humidity. That is why it is best to LEARN how to thin paint rather than develop a certain formula to follow. A good clue can be air pressure, a good batch should flow through the airbrush at 10 to 15 psi any higher and your too thick.

[Oceaneer99]

When I had the pressure too high for my first try on the white paint, the result was a rough surface (orange peel) because the paint partially dried in the air.

I have discovered that some of the flow enhancers have retarders for the very reasons that Ray stated.  I found this out while thinning paint for brushing.  I went too far with the thinning and the paint never dried because there was too much retarder!  Re-reading the instructions, I should have thinned with water and a little bit of flow enhancer.

Garet

[Oceaneer99]

Much to my surprise, I found that I have BOTH Golden's airbrush medium and their acrylic flow release.  I think it is the flow release that I've been adding to my craft paints when I want to use a paintbrush with them.

I did some testing with a jar of Delta Ceramcoat Dolphin Gray (the stuff I use for my ID models).  I painted samples of each mix on a piece of plastic so that I could take a look at texture.

Delta by itself was very thick, left bad brush strokes

Delta + a few drops of acrylic flow release left noticeable brush strokes, though not as bad as the Delta alone

Delta + Paint Easy (roughly 4:1) went on nicely, dried with minor brush strokes

Delta + Tamiya thinner went on nicely, dried very flat, only very minor brush strokes

I made another mix, of Delta with Golden's airbush medium and Tamiya thinner, and it never dried!

I'm working out some ideas for a more complete test, to include layering one type of paint over another (to look for things like Model Master over Tamiya causing awful cracking and crazing.

Garet