Paint drops

i learned that the hard way, which really is the best way if you are starting out with an inexpensive model. i have an old mk-iv hull i hit first to see if i have the tight thickness. then i hait a piece of cardbaord before hitting the model. i still go to fast and sometimes end up with runs like today just doing touchup on an LVT-(A)-4 base color (nato tac tan) before camo. so my touch up will now be another coat after i sand down the runs. very frustrating. had some orange peel on an LVT-2 (blue gray) that i touched up before the a-4. hopefully that will be good and i can put the track on and build the upper hull.

just takes a while to get good. and i really need to get good quickly because the stash of "can't build until i airbrush" is building up.

Bgrigg

Mrmike's point was that if you are setting the "proper" pressure at a regulator on a compressor 25' away, you will NOT get that pressure at the working end of the hose!

I know what he was saying Bill and I just have not seen that happen personally that I can remember. When I set my old 1-1/2 hp compressor at 80 psi and ran 50' feet of hose to the garage to my airbrush I still got 80 psi with my regulator turned up all the way. I am not saying it can't happen, I am just saying that I don't remember experiencing that, but then again that was several years back and I could be wrong.

Those charts were to show how much loss you can experience, even with high powered compressors, and weren't meant for airbrush application.

Mrmike's point was that if you are setting the "proper" pressure at a regulator on a compressor 25' away, you will NOT get that pressure at the working end of the hose!

Regardless of the starting CFM, you will encounter friction loss over the length of the run. The smaller the CFM number, the more profound the loss. That's why you shouldn't hook up a 20' hose to a tiny compressor, and why you should set the air pressure while holding down the trigger.

Think about it this way, blow into a regular soda pop straw. Feel the air coming out the other side. Now find some hoses 1', 2' 3', & 6' long and compare.

I have my regulator mounted in my booth, and the shortest possible hose that still gives me freedom of movement. If I were to change out my 6' hose for a 10' hose, I would have to crank up the pressure to compensate.

Bgrigg

Pressure loss in hoses is a fact of life. Be it caused by friction, bends, kinks and fittings (especially quick connects!). All materials pressurized (air, water, oil, gas etc.) experience loss over long runs, especially with rubber, plastic or vinyl hoses. Steel lines will lose pressure, but at a lesser rate.

Compare these charts for rubber or steel lines for pneumatic tools.

You also get loss of air movement in vents. Consider that flexible ducting is a poor choice for vents, due to the very large amount of friction caused by the internal structure.

True Bill but we are talking about airbrushes here, not an impact gun or a jackhammer.

Also, those charts start at 10 CFM which is far more than any airbrush is capable of so unless your compressor is woefully underpowered the air pressure drop is going to be marginal with an airbrush.

Pressure loss in hoses is a fact of life. Be it caused by friction, bends, kinks and fittings (especially quick connects!). All materials pressurized (air, water, oil, gas etc.) experience loss over long runs, especially with rubber, plastic or vinyl hoses. Steel lines will lose pressure, but at a lesser rate.

Compare these charts for rubber or steel lines for pneumatic tools.

You also get loss of air movement in vents. Consider that flexible ducting is a poor choice for vents, due to the very large amount of friction caused by the internal structure.

mrmike

The air pressure issue is kind of subjective, since the longer the distance from the compressor to the gun, the more pressure drop you get. If you're 25 ft or more away, the indicated pressure at the compressor doesn't tell you how much air you're really working with.

Where did you hear that? I have never heard anyone say that and that surely has not been the case when I had my compressor in a shed in the back yard and ran a 50' air hose to my garage to airbrush T-shirts.

I use a VL which I've owned since too long ago to mention. Most of the time the spatters and drops have been caused by a worn or damaged needle, or accumulated dry gunk in the tip. (I've needed a spatter effect at times, and used an old needle roughed up with 120 grit to achieve it).

There was a recent article in FSM about fine tuning your AB, which had some great techniques. The air pressure issue is kind of subjective, since the longer the distance from the compressor to the gun, the more pressure drop you get. If you're 25 ft or more away, the indicated pressure at the compressor doesn't tell you how much air you're really working with. In that case, the best thing to do is use a small inline pressure gauge where your AB hose connects to the air line.

Hope this helps!

Guys, I am really sorry for the late response, but thanks to all for helping me out on this.

HawkeyeHobbies

WAY TOO MUCH PRESSURE!!!  Get your pressure down to somewhere between 12-18 psi.

Not with a siphon-feed airbrush like the Paasche with a heavy tip and needle.

Paasche's are notorious for needing higher pressures to spray well, at least the VL model is.

WAY TOO MUCH PRESSURE!!!  Get your pressure down to somewhere between 12-18 psi.

The H5 is meant for broad coverage or higher viscosity medims.  I use the H3 about 90% of the time & it works fine with enamels.  So does the H1 if you need a finer spray.  You may have to adjust your thinning ratios or psi to get optimal results.  I usually thin for spraying at 20psi with the H3 & about 15psi with the H1.  The smaller the nozzle, the more thinning required.  Clean up after spraying enamels is best done with Lacquer thinner.

Regards,  Rick

Thanks for the help. What about the H-3 nozzle, will this work for enamels or should I stick with the H-5?

A little spatter is to be expected when starting the air on any airbrush.

It's always advisable to start the airflow with the brush pointed away from your model, though this may be difficult to do if you're doing freehand mottle camo using a single-action brush.

Thanks for the reply. These paint drops though appeared at the very start though, before paint could even collect. However, being a newbie with the airbrush I will keep your advice in mind.

always start spraying off the model to avoid the drops, they collect on the end of the needle. also i clean the head and needle with thinner soaked q tip when the paint gets thick.'

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