External Mix vs. Internal Mix air brush?

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deanej

Member
We had a great and useful discussion in the thread I started on cleaning solvents for air brushes, and now I have a different issue I could use some input on.

For years I used a Paasche H series external air brush. In those days it was almost always lacquer based Floquil or Scalecoat. Loved it, but it began to spatter paint and I couldn't locate the reason. I bought a new one, but decided to try an internal mix Paasche SA2000. Nice and smooth, but much harder to clean than the old external mix H series. Harder to adjust also.

As I return to modeling after a 10 year hiatus, I discover I have developed a severe allergy to lacquer thinner. My days of spraying Scalecoat are over.

As I began using Modelflex and Polly Scale, I discover they dry up and clog the airbrush rather quickly, and are very hard to clean out of the internal mix Paasche. I may need to purchase an external mix, even though they don't seem quite as smooth in application as the internal mix.

What are your experiences? Is the difference in clogging and cleaning enough that I should invest in an external mix and put the internal mix aside? If so, which H# nozzle works best with acrylics?

And the tough question might be, is there a better brand to be used exclusively with water based paints than Paasche? That's all I've used for 40 years, so Paasche is all I know.

I look forward to your comments on this issue. There's nothing like the voices of experience.
 

Graff

Airbrush artist
The main reasons for clogging up of acrylic paints is:
-Too thick mixture
-Old paint
-Unstrained paint
-High temperature
-Too much air pressure
-"bad" paint (i.e. some brands are not as good to use as others....)
I have been working proffesionally with Airbrushing for almost 20 years, and have learned along the way to appreciate the benefits of using acrylic paints AND internal mix Airbrushes!
I ALWAYS use an Acrylic extender mixed with the paint, it almost eliminates the tip drying.
I ALWAYS strain the paint! That has eliminated the unavoidable pigment clumps that you almost always have in acrylic paints.
I have also started to use Vallejo Model-Air paints almost exclusively now as they are so much better to use......
 
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deanej

Member
Indeed, the paint is old. Probably close to 10 years on the shelf.

Thick is something I need to learn to judge, so I don't know.

Temp was about 75 degrees.

Air pressure was about 30 lbs

Brand was Badger Modelflex

No acrylic extender was used. I assume this is the same as retarder.


I appreciate your suggestions. It would seem that I have some things to work on.
 

Graff

Airbrush artist
Indeed, the paint is old. Probably close to 10 years on the shelf.

Thick is something I need to learn to judge, so I don't know.

Temp was about 75 degrees.

Air pressure was about 30 lbs

Brand was Badger Modelflex

No acrylic extender was used. I assume this is the same as retarder.


I appreciate your suggestions. It would seem that I have some things to work on.
!0 years is a bit on the far end of the shelf life... :D
Thickness is tricky... It depends on so many factors:
Air pressure, distance to the object when painting, line painting or wide coverage etc. etc.
Temp seems okay.
Air pressure is also depending on the same different factors as paint thickness....
Badgers Modelflex is in my opinion better to Airbrush than Polly-S.....
Acrylic extender is the same as retarder. I use Liquitex brand, as I find it very good.
 

Espeefan

Well-Known Member
On external mix:

Good to learn with. Nice for beginners. Limited capability.
On internal mix: they atomize the paint better. Finer spray pattern, better control. Siphon feeders are as a rule harder to clean. You might try a gravity feeder like the Paasche Talon. Gravity feeders are much easier to clean than siphon feeders.

Better brand? That's a matter of taste. Badger is good. I learned on those. Paasche is also good. I have three, the H, the VL and the Millenium. I use the Millenium most of the Passches. These days I mostly use Iwatas. I like the Eclipse CS. The airbrush should feel good in your hand and be easy to control. After that brand doesn't matter much. Generally speaking the higher the cost, the finer line the gun will lay down.

You're experiencing the same transition pains as any of us who switched from enamels & lacquers to acrylics. Do use the extender. Tip dry requires cleaning of the needle. That's why I like Iwatas. The nozzle cap comes off and I can wipe off tip dry as I paint.

On paint thickness: Think of milk. Thin your paint to the consistently of milk and it will spray just fine. Badger's paints are airbrush ready except for adding the extender. Put a dropper full in each bottle and you're good to go.

Hang in there. You'll pick it up!
 
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deanej

Member
Some heavy advice here guys. Thanks a lot. It's giving me a foundation for figuring out how to move ahead with acrylics.

My favorite for air brushing was the original Floquil lacquer. Hard to mess up and very controllable. So far, I'm finding the acrylics a little bit like using a garden hose for a Water Pik. I know it's just a matter of getting the feel for it.

Unfortunately, none of the local hobby shops carry Modelflex. I sort of zeroed in on it since you can decal directly on it. I hate to add a layer of gloss on anything before decals, then having to add a layer of flat. Too many layers of paint over fine detail. That was one of the good things about Scalecoat.

In running some tests, I happened to have a small bottle of Polly Scale flat and tried it. Doesn't seem as flat as good old Testers Dull Coat which I had always used. I'll try to find some Microscale flat tomorrow. Anyone have another brand that's more like the Dull Coat?

Deane
 

frog

Member
The only airbrush I have used is one of these Testor plastic ones, el cheapo. External mix, I am sure you know what type. It has worked fine for painting scale buildings and rail cars, but I am thinking about going to a double action of some sort.

Not train related, but I have some plane models that have the over and under colors meeting in a misty pattern, something you could do on a full size plane with a can of spray paint. Would I need a double action to do this on a model? I don't see how I can do it with my external as the pattern would be too broad.
 

Cjcrescent

Master Mechanic
Deane;

Are you allergic to just lacquer thinner, or all solvents? Reason I ask is Floquil is no longer lacquer based.

Both Floquil and Scalecoat I & II thin with Xylol and/or Tuolol. Of course when painting with any solvent based paint, its best to always use a respirator and a paint booth when painting inside the garage, workshop or any enclosed space. I would also use one even when painting outside.
 

deanej

Member
Deane;

Are you allergic to just lacquer thinner, or all solvents? Reason I ask is Floquil is no longer lacquer based.

Both Floquil and Scalecoat I & II thin with Xylol and/or Tuolol. Of course when painting with any solvent based paint, its best to always use a respirator and a paint booth when painting inside the garage, workshop or any enclosed space. I would also use one even when painting outside.
The allergy is extending to all sorts of things including household cleaning solvents. With careful testing, I've concluded that the worst reaction is to CA glue. Exposure creates a reaction that lasts 3 or 4 days. I switched to oderless CA and that appears to work pretty well.

Once all of this is out of my system, I'll try Scalecoat again. It's too good a paint not to try to use. I hate not being able to use lacquer thinner, as it's such a good clean up solvent, even with acrylics.

As I searched around the internet for comments on this issue, I discovered a lot of discussion on the model airplane forums about CA glue allergy. The thought is that it will hit almost everyone after extensive use of CA over a period of multiple years.
 

frog

Member
Is it better when buy a double action to get one with different needles for flow width? I need one with a very thin flow to paint aircraft models in order to get the "blended" camo look on the wings. This would also be best for weathering RR cars I would think.

As for wider patterns I could maybe use my cheap Testors for those applications.

As for 'double action", are these the same as "internal mix" or do some single actions also have internal mix? Miy Testors is external, I know that.
 

Espeefan

Well-Known Member
There are single action internal mix airbrushes. The Badger 200 is a good example. I am not aware of any double action external mix guns.

Multiple needles and tips are not necessary for a good range of coverage. I have a Paasche Millenium and an Iwata Eclipse HP-CS that will do fine pencil lines to 3/4" wide lines, all with one needle.

Double action lets you change the line width on the fly. With single action, you stop and adjust the spray volume. Overall double action allows you more versatility. It takes a little more to learn double action, about like switching from automatic to a stick shift. You may have an oops moment or two, but you'll pick it up in no time. All it takes is practice.
 

frog

Member
I thank you for that. It clears up some confusion and now I have a good idea of the type I need to get. I am leaning toward a gravity type, with the cup at the top. Looks easy to spill but I do my spraying outside anyway, and it would save paint and be much easier to clean.
Most of my paint will be solvent based but I do use water base sometimes.

Thanks again.
 

Espeefan

Well-Known Member
No problem. Good quality gravity feed guns come with a cap for the cup to prevent spills. Gravity feeders are also very easy to clean. Not sure of your budget but the Iwata HP-CS is an excellent airbrish. See it here:

http://www.iwata-medea.com/index.php/products/hp_cs

If you are in the Chicago area, come out to the Dupage Fairgrounds to the Great Midwest Train Show next week. I'll be there demonstrating them.
 

frog

Member
I found a Badger Patriot 105 new for $79. It is internal gravity fed with a cover for the cup. The price is after a coupon, is this a good airbrush?

If so I plan on getting it today as the coupon expires pretty quick.

(Badger is the only brand they have.)
 




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