Moisture from airbrush even with moisture trap

[tmathew1us]

I have a compressor, regulator with  moisture trap, and Iwata dual action airbrush. I usually spray at around 25-35 psi. I use about a 6 foot hose.  After about a half hour or more of airbrushing , I often get spurts of water coming out of the airbrush, which is ruining my finishes. This appears to be pure water, and I typically spray enamel or 2 part clear. 

I have checked and emptied the moisture trap with the release valve, and this still often happens. 

I recently changed to a new regulator/moisture trap, sealed with teflon. Still with the same problem

Any suggestions?

[Psychographic]

If like most airbrush compressors that come with a trap, it has it located at the compressor or tank, you need to move the trap. The trap has to be far enough away from the source so it can cool and the water separates from the air. What is happening is the warm moist air passes right through the trap and as it cools in the line and airbrush the water separates from the air.  What I do is run a 6foot line from my compressor to the moisture trap and then hook my airbrush hose the trap.

 

 

[935k3]

You might want to get this Water Trap   It attaches directly to the airbrush

[Ace-Garageguy]

Psychographic has the right idea. The FARTHER you can get the trap from the compressor, the better.

In the real world, we run air through a heat-exchanger to cool it as much as possible before running it into the booth, where the big water trap lives, and we run disposable final traps on the guns, as 935k3 suggests as well.

 

[tmathew1us]

Thanks so much for the info, Bill,, Dale and David.

So if I am understanding this right, as the compressor gets hotter (ie. the longer it runs), the more likely it is to pass hot air which holds moisture to the airbrush? 

I wonder if giving the compressor a chance to cool off, say not going more than 15 min at a time, would help? I will add in a trap closer to the airbrush.

Is there any point to having 2 traps, the one attached to the compressor as I have it set up, and another to the airbrush? or is that too much for the compressor to push air through?

[Psychographic]

I wouldn't trust letting the compressor cool off as a remedy. On a very humid day it doesn't take long for moisture to build up. Don't forget you are compressing the air which means you are also adding more moisture. You shouldn't have a problem with two traps, but as i said unless you move the first one, it's pretty much useless and it's easy to forget to check the traps. Relying on just that small one at the airbrush is risky. You are in Florida, not exactly a cool or dry place.

Edited May 13, 2018 by Psychographic

[Art Anderson]

18 hours ago, Psychographic said:

I wouldn't trust letting the compressor cool off as a remedy. On a very humid day it doesn't take long for moisture to build up. Don't forget you are compressing the air which means you are also adding more moisture. You shouldn't have a problem with two traps, but as i said unless you move the first one, it's pretty much useless and it's easy to forget to check the traps. Relying on just that small one at the airbrush is risky. You are in Florida, not exactly a cool or dry place.

Uh in summer, here in IN, the humidity can be just as bad as in Florida (Sorry, Floridians, you do NOT have a monopoly on humidity, regardless of your opinion!).  Any moisture trap NEEDS to be a distance down line from an air compressor, in our environment--mine is at the end of a 6" hose from the air compressor (the trap and that hose are now well over 50 yrs old, BTW), and that setup has NEVER betrayed me.

Art

[Art Anderson]

18 hours ago, Psychographic said:

I wouldn't trust letting the compressor cool off as a remedy. On a very humid day it doesn't take long for moisture to build up. Don't forget you are compressing the air which means you are also adding more moisture. You shouldn't have a problem with two traps, but as i said unless you move the first one, it's pretty much useless and it's easy to forget to check the traps. Relying on just that small one at the airbrush is risky. You are in Florida, not exactly a cool or dry place.

Actually, this is an "Old Wive's" tale.   When you compress air, it gets warmed up (did you ever take Physics in HS or College?), and when you release that pressure, it cools way off (Again, did you ever take physics in HS or college?).  i don't give a BLAH_BLAH_BLAH_BLAH what any airbrush/air compressor manufacturer or seller tries to say--a moisture trap needs to be separated, downline from the compressor, period.  I have a 30-yr old Binks air compressor, which is connected to a 6' hose to a  Binks water trap that I bought way back in 1962 (!), with a hose from there to my airbrush.  Not in more than 50 yrs have I had any issue with moisture interfering with my airbrushing, PERIOD, end of statement!

[Ace-Garageguy]

20 hours ago, tmathew1us said:

...So if I am understanding this right, as the compressor gets hotter (ie. the longer it runs), the more likely it is to pass hot air which holds moisture to the airbrush? 

The issue isn't the compressor getting hot.

Here's the science.

Air gets hotter as it's compressed. Always. Basic. If there's water vapor in the air, called humidity, it gets compressed too.

The air COOLS in the line going out of the compressor.

Cooler air can't hold as much water vapor as hotter air, so liquid water condenses in the line.

Putting the trap as far as is practical from the compressor, so you're getting the cooler air, works best.

Art is a little off the mark.

The pressure is reduced and the air cools even MORE as it goes through the air-brush nozzle and expands.

The cooling can be so great that liquid water will actually condense on the surface of what you're painting.

ONE byproduct of this is commonly called "blushing" of sprayed lacquer.

 

Edited May 13, 2018 by Ace-Garageguy

[Psychographic]

22 minutes ago, Art Anderson said:

Actually, this is an "Old Wive's" tale.   When you compress air, it gets warmed up (did you ever take Physics in HS or College?), and when you release that pressure, it cools way off (Again, did you ever take physics in HS or college?).  i don't give a BLAH_BLAH_BLAH_BLAH what any airbrush/air compressor manufacturer or seller tries to say--a moisture trap needs to be separated, downline from the compressor, period.  I have a 30-yr old Binks air compressor, which is connected to a 6' hose to a  Binks water trap that I bought way back in 1962 (!), with a hose from there to my airbrush.  Not in more than 50 yrs have I had any issue with moisture interfering with my airbrushing, PERIOD, end of statement!

You do realize what you just  replied in your "smarter than me" attitude is exactly the same thing I said in my original post? In fact I even said I used a 6 foot line from my compressor to the trap, just like you use.

Edited May 13, 2018 by Psychographic

[Art Anderson]

16 minutes ago, Ace-Garageguy said:

The issue isn't the compressor getting hot.

Here's the science.

Air gets hotter as it's compressed. Always. Basic. If there's water vapor in the air, called humidity, it gets compressed too.

The air COOLS in the line going out of the compressor.

Cooler air can't hold as much water vapor as hotter air, so liquid water condenses in the line.

Putting the trap as far as is practical from the compressor, so you're getting the cooler air, works best.

Art is a little off the mark.

The pressure is reduced and the air cools even MORE as it goes through the air-brush nozzle and expands.

The cooling can be so great that liquid water will actually condense on the surface of what you're painting.

ONE byproduct of this is commonly called "blushing" of sprayed lacquer.

 

Gee, Bill!  I've had a water trap on my air line since 1963, and I live in Indiana, which from spring to late fall can be as humid as Florida (trust me on that one), and "blush" from my perspective, has always happened from the ambient air, NOT from air in my compressed air line.  Now "blush" as I have seen it comes from my entrenched "layman" knowledge/experience, as opposed to the professional experience from you, and the numerous professional spray painters I have known over my 74 yrs of life.  BTW, my moisture (water) trap has been connected to the various compressors I have used, since early 1963, bu a minimum of SIX feet of hose, OK--and it's done its job perfectly ever since.

Art

 

 

[Ace-Garageguy]

12 minutes ago, Art Anderson said:

Gee, Bill!  I've had a water trap on my air line since 1963, and I live in Indiana, which from spring to late fall can be as humid as Florida (trust me on that one), and "blush" from my perspective, has always happened from the ambient air, NOT from air in my compressed air line.  Now "blush" as I have seen it comes from my entrenched "layman" knowledge/experience, as opposed to the professional experience from you, and the numerous professional spray painters I have known over my 74 yrs of life.  BTW, my moisture (water) trap has been connected to the various compressors I have used, since early 1963, bu a minimum of SIX feet of hose, OK--and it's done its job perfectly ever since.

Art

The rapid expansion of the air as it goes through the nozzle may have two distinct condensation effects:

1) IF there's still water vapor in the compressed air, it may very well condense on the surface of what you're spraying, especially if the surface is cooler than the air coming out of the nozzle, with blushing as a possible result.

2) IF the air coming out of the nozzle is dry, there is STILL a pronounced cooling effect, and this can cause ambient water vapor (humidity in the air) to condense on the surface, with blushing as a possible result.

 

[peteski]

10 hours ago, Ace-Garageguy said:

2) IF the air coming out of the nozzle is dry, there is STILL a pronounced cooling effect, and this can cause ambient water vapor (humidity in the air) to condense on the surface, with blushing as a possible result.

 

Yes, this can happen on hot and humid days. Even when dry compressed air leaves the airbrush nozzle (mixed with atomized paint), it cools down.  If the warm and humid ambient air has enough moisture in it, the cool stream of air coming out of the airbrush will mix with the ambient air forming water droplets which will end up in the surface being painted. For that reason I never airbrush on hot and humid days.