# Two questions: lumpy paint & compressor regulator



## JackM (Jul 29, 2008)

This really follows my questions under "Grex airbrush" back in January, but I'm not using a Grex, so I figured I should start a new thread -----------


I spent some quality time yesterday with my cheapo Harbor Freight airbrush and my UNDECorated US Trains S4 and I'm very pleased with the results so far, but two things came up in the process. 

Yesterday's project was to spray a fairly dark gray on the inside/underside on the three main pieces: engine hood, cab and underbody. I got a nice, smooth coating, encouraging me that I'll end up with a nicely painted S4. But two questions: 

1 - What's the secret to mixing acrylic paint? After many, many minutes stiring the brand new bottle of Polly-whatever and adding 10% water according to bottle directions, followed by enough shaking the bottle to annoy my carpal tunnel, I still see little lumps when I pour it into my airbrush bottle. (I've read that you shouldn't shake acrylics. Really?) What should I be doing to get all the pigment mixed in properly? 

2 - For air, I hooked a long hose to my medium-size compressor in the garage: 8 gallon, 100 psi max. Working down in the basement, there's enough concrete and cinder block that I can't hear the compressor run at all. I also have a regulator and moisture filter downstairs, in front of the airbrush. But I can't set it to give me a constant pressure (say, 20 psi). Seems like I must be readjusting it whenever the compressor is low enough to kick in the motor, around 70 psi, I think. I would expect to get a constant 20 at the brush as long as the compressor tank has something over, say, 40 or 50 psi. Is the regulator at the airbrush a twelve dollar piece of junk, or....I don't know what else. 

I'll be getting ready to start the exterior painting, hopefully, this weekend. Any suggestions would be appreciated, as always.


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## Spule 4 (Jan 2, 2008)

Polly S is bogger laden unless you screen it, not a fan of the stuff actually. Some colors were worse than others. 

Sneak in and steal a pair of stockings from the Mrs., just let her know nothing creepy is going on. Never heard not to shake it, but whatever. 

Pressure regulation at a constant can be a problem, I have a large compressor with very large tank (airbrusing is not its primary function, automotive workshop tools is its main function) and have the same problem. What can help is a home made "manifold" iwith an additional gauge for the airbrush from the main line of the tnak where you can see it while painting. Helps tell if you are loosing pressure. 

Not sure about the Harbor Freight airbrush, I know they had one that was a knock off of the Paasche H? I have an H and would not trade it for the world.


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## armorsmith (Jun 1, 2008)

Jack 

Lets start with the air supply. 

First, what size is the hose between the compressor and the air brush, and how long? The longer the hose, the higher the pressure drop to reach the regulator. The smaller in diameter the hose the higher the pressure drop. Smaller hose and longer run means even higher pressure drop. Do you have a pressure gauge at the regulator? What does it read at full compressor pressure and how much does it drop when you start spraying? Read the paperwork that came with the regulator, there should be a minimum delta pressure specified for supply vs regulated pressure, and a pressure drop across the regulator. Also read the specs for the moisture separator, it will also have a pressure drop across the filter. It almost sounds like your supply perssure (after pressure drop) is below the minimum delta of the regulator. 

As an example, if you wanted 20PSI at the air brush, follow.... 

Moisture Separator has a 5 PSI pressure drop 
Regulator has a 5 PSI pressure drop and a 20 PSI minimum delta pressure. 
Your long, small hose is losing 20 PSI from the compressor to the regulator. 

The minimum required pressure at the compressor reservoir would be 20 + 5 + 5 + 20 + 20 = 70 PSI. 

Keep in mind the numbers above are for demonstration only. The only number that is real is the 20 PSI you are trying to attain at the air brush. 

My first inclination to solve the pressure issue would be to go to your local industrial hose distributor and purchase the requisite length of 1/2" id hose with ends. 

As for mixing the paint, I have a couple of small stainless steel ball bearings I keep on hand to drop in the jar/can before mixing - kinda like a rattle can. 

Good luck! 

Bob C.


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## JackM (Jul 29, 2008)

Since I haven't had a Mrs. for quite some time, I don't have access to the proper straining material, but I can easily substitute a few stainless steel nuts for the ball bearings. Why didn't I think of that?

Not sure what the deal is with the air pressure. This evening I adjusted the garage compressor to exactly 100 psi; motor starts up when it drops below 70. I also added quite a bit of oil to the motor. The hose is 50 feet of 1/4 inch, but the regulator guage in front of the airbrush indicates almost 100 psi when the tank is fully charged. I hooked up the airbrush but without paint bottle and I didn't have too much trouble adjusting the reg. to 20 psi and keeping it there.

But isn't the regulator supposed to limit the pressure? I would expect that even when there's 100 psi coming down the hose, I should be able to set the regulator to 20 psi and never see more than that. No? Before I press the trigger on the brush, pressure is whatever's coming down the hose (as much as 70-100 psi). After I press the trigger, pressure takes 5-6 seconds to drop to the desired 20 psi. Seems like the regulator is setting the minimum, not the max.


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## dawgnabbit (Jan 2, 2008)

Posted By JackM on 03 Mar 2010 09:12 PM 


But isn't the regulator supposed to limit the pressure? I would expect that even when there's 100 psi coming down the hose, I should be able to set the regulator to 20 psi and never see more than that. No? Before I press the trigger on the brush, pressure is whatever's coming down the hose (as much as 70-100 psi). After I press the trigger, pressure takes 5-6 seconds to drop to the desired 20 psi. Seems like the regulator is setting the minimum, not the max.



Jack, 

Are you saying the pressure drops from 100 psi DOWNSTREAM of the regulator to the desired 20 psi??? If so, you have a faulty regulator. A regulator should never pass source pressure through to the regulated side whether air is flowing or not (unless the source pressure is less than your set point, of course). Try a different regulator--they're pretty cheap at Lowes these days. 

For mixing paint without shaking, Badger makes an inexpensive* paint stirrer* that does a wonderful job and only costs a few bucks. Much faster than shaking. Just remember to turn it off before you pull it out of the bottle.









Regards,

Dawg


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## dawgnabbit (Jan 2, 2008)

Um, one more thing. I almost hate to ask this, but...

You DO have the regulator installed right way around, correct? They don't work worth a patutium rodentia if they're backwards. Don't ask me how I know lthis.


Dawg


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## JackM (Jul 29, 2008)

I was thinking that I've seen a little paint mixer like you describe, but couldn't recall where I saw it. Klutz that I am, the picture of me pulling it out of the paint while still spinning makes me wonder if it'd be a good idea to NOT get one.

The regulator: I just went down to check. The arrow on the underside is pointing toward the airbrush. When the compressor is pumped up, I open the regulator knob a bunch of tunrs , hear a small woosh, and the gauge flies up to 100 psi. I turn the knob back a couple turns. When I first press the trigger on the airbrush, the reg. gauge drops from 100 toward zero. While holding the trigger open, I adjust the gauge to, say 20 psi. Let go of the trigger and the guage goes back up to 100. Press the trigger and the guage takes 2-3 seconds to drop to 20 psi. Anytime I let up on the trigger for just a second, the guage heads back toward 100 then drops back toward 20 as soon as I press the trigger again.

That doesn't seem right, but then I'm new at this.

jack


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## hawkeye2 (Jan 6, 2008)

It's quite possible you have an internal leak from the high side to the low side of your regulator. The leak is small enough so that it transmits pressure but no great volume. You see the pressure at the airbrush rise over a short time then drop to regulated pressure a few seconds after you trigger the brush. It's probably is a dirty or dammaged seat in the regulator and if it isn't crimped together you could dissamble it (it is spring loaded) and check. Another solution is to add a "T" in the line just before the airbrush with one leg vented to atmospheric. Open the T slightly just before you start spraying to bleed off excess pressure and you could probably leave it cracked slightly if it doesn't bother you. The best solution is to unscrew the regulator and drop it in the trash on your way out the door to buy another.


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## dawgnabbit (Jan 2, 2008)

Jack,

If the arrow is pointing in the right direction (it is) then your REGULATOR IS FAULTY, period. Generally when they start to go bad, trying to repair is a waste of time. Just bite the bullet and REPLACE it.

Here's the one I use; It works very well, doesn't cost much, and should be available at any Lowe's store. Home Depot sells a virtually identical one.


As far as removing the stirrer too early goes, you will only make that mistake once in your life. Guaranteed.

Dawg


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## Tenwheeler (Mar 5, 2010)

Re paint stirrer...

Several years ago I purchased a paint shacker from Micro Mark. I did a quick search of MM and they still sell one with AC/DC converter, Robart Model #411. Tower Hobbies had the same model, but at a better price. Amazon sells a similar model, Robart Model #410, only it is battery operated - about $22.00.

My paint shacker has several hours of operation and still works great. I typically use Floquil paint and always get a good mix with the shacker.

I also saw a home made paint shacker doing a Google search that looked like it would do the trick also: http://modelingmadness.com/others/f...mmixer.htm

My recommendation... buy a shacker , they work great and don't cause bodily harm.









Jerry
"Pour the coal to her, she don't leak"


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## dawgnabbit (Jan 2, 2008)

Jerry, 

Hamm's carving knife cum shaker/sander is a truly clever gadget! Thanks for the link. 

I wonder if that's where the Fein Multimaster people got the idea. LOL 

Dawg


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## JackM (Jul 29, 2008)

I ended up putting a couple SS nuts in each paint bottle. Worked like a charm. 

Dawg - I got 80% of my painting done this weekend. Nothing like an actual pressure regulator (as opposed to one that *calls* itself a pressure regulator) to get things running smoothly. 

Thanks for everybody's suggestions. I should have the S4 done in a week or so; will post photos. 

jack


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