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So here is the case. I have a cheapo compressor and I have a 20 Dollar airbrush. I have minor problems when spray alcoholic paints such as Tamiya or Gunzee, but when I try acrylics (apart from Vallejo Air) the result is not that good.
I tried to spray GW paint with a good mix of Vallejo Flow Improve and a bit water. I usually don't have issues with such combination but it started to spray water... like a lot of water. Maybe my thinning was not correct, but even when I added large amount of thick paint the result was the same. The paint hit the surface in large water drops and have nothing to do with the results of airbrush videos. Maybe I should switch exclusively to Vallejo Air and Gunzee and don't better with non air acrylics, but what I noticed was a lot of water in my Moisture trap. Could the problem actually be that I need another moisture trap attached to the airbrush? Or maybe I need new and better airbrush...

EDIT: I tried to spray Russ Grey, which is layer paint and is too transparent even when brushed on.

The moisture trap should have a drain to drain out the water. Also if you're using a tanked compressor, find the drain plug and drain that out too.

Whether you need another moisture trap or not, I dunno, I'm still using the same trap I got with the compressor and it still works, I just drain it occasionally and it's still working. If you're in a humid enough area you might need a replacement or even 2 separate traps.

It is a thankless compressor, for now. I was planning to add a tank and buy Iwata brush later on, because I don't think that the compressor is all that essential.
https://sc01.alicdn.com/kf/HTB19Aa6LpXXXXchaXXXq6xXFXXX1/1-6-HP-hobby-tools-hseng-AS18C.jpg

Vent water out of the bottom of the compressor tank, drain any visible water out of the trap and yes, consider a second trap.

I have one just off my compressor/regulator and then I have a second just after my fine-tune regulator just before the airbrush hose.

Where do you operate your compressor? I am a basement dweller for my hobbies and we keep the dehumidifiers running down there. about 40-50% humidity is about right, 60% it starts to get to be a bit much (fogging of windows, musty basement smell). Got anything to measure your humidity level? You do not live next to the Black Sea do you?

 Talizvar wrote:
Vent water out of the bottom of the compressor tank, drain any visible water out of the trap and yes, consider a second trap.

I have one just off my compressor/regulator and then I have a second just after my fine-tune regulator just before the airbrush hose.

Where do you operate your compressor? I am a basement dweller for my hobbies and we keep the dehumidifiers running down there. about 40-50% humidity is about right, 60% it starts to get to be a bit much (fogging of windows, musty basement smell). Got anything to measure your humidity level? You do not live next to the Black Sea do you?

It is tankless, but I guess it gets a lot of moisture :(
Nah, I am living faar from the coast lane and I live on the 8th Floor where moisture it should not be that much...

Wow, did some digging into the physics of all this.
Compressed air "should" not effect how much moisture the air holds.
BUT the compressor heats the air as it works, which has a direct impact on it holding more moisture.
Something as simple as putting the compressor on the floor rather than on a shelf may help this.
Compressors that do not have a holding tank must run constantly which can cause them to heat-up: adding more moisture to the air.

Something to keep in mind for those who do not keep the compressor in the same room: keep compressor in cooler place, painting to happen in warmer place.

Your first moisture trap will heat up with the rest of the compressor which will decrease it's efficiency (bigger the difference in temperature = the better it works).
Having a second trap well away from the compressor should work well, even better if in the path of a fan you use for ventilation anyway.
Funny, my second trap is mounted on the wall next to cement blocks in the basement so it is already kept cooler because of that.

Only other thing is running at a high flow rate / high pressure: what pressures you running at?

All I can think of.

 Talizvar wrote:
Wow, did some digging into the physics of all this.
Compressed air "should" not effect how much moisture the air holds.
BUT the compressor heats the air as it works, which has a direct impact on it holding more moisture.
Something as simple as putting the compressor on the floor rather than on a shelf may help this.
Compressors that do not have a holding tank must run constantly which can cause them to heat-up: adding more moisture to the air.

Something to keep in mind for those who do not keep the compressor in the same room: keep compressor in cooler place, painting to happen in warmer place.

Your first moisture trap will heat up with the rest of the compressor which will decrease it's efficiency (bigger the difference in temperature = the better it works).
Having a second trap well away from the compressor should work well, even better if in the path of a fan you use for ventilation anyway.
Funny, my second trap is mounted on the wall next to cement blocks in the basement so it is already kept cooler because of that.

Only other thing is running at a high flow rate / high pressure: what pressures you running at?

All I can think of.

I am keeping it on a shelf, and because there is no Tank it gets overheated pretty fast. Maybe this is the whole problem :( I will place on the ground, below the desk and hope it will get better.
Meanwhile I've purchased second moisture trap.

Pressure is depend on the paints I am using, but that will be everything between 15 and 30 PSI.

Normal pressure range.

The compressor running hot is a problem.
maybe have an inexpensive small fan blow on it while it runs?

Root cause is still warmer air going in, air on it's way out being cooler and moisture condensing out.

I hope the second vapor trap works, you may still be stuck with emptying them out often.

 Talizvar wrote:
Compressed air "should" not effect how much moisture the air holds.

Where abouts are you reading that? It's been a while since I studied thermodynamics but I thought the dew point is affected by pressure, and phase change diagrams are often drawn as pressure on one axis and temperature on the other, or temperature on one axis and entropy on the other with multiple curves drawn at different isobars (ie. different pressures).

As I said it's been a while since I did thermodynamics, but doesn't compressing air cause the dew point to rise, but you're also heating the air which opposes the rise in pressure, then as the air cools in the tank or lines but still at an elevated pressure the higher dew point kicks in causing condensation to form in the tank/lines.

The temperature change is why you want the moisture trap near the airbrush, as the air cools more moisture condenses out of the air. If you have a tank you can often get away with just having a moisture trap downstream of the tank, because the tank is a plenum where the air is allowed to be cooled before passing through the lines. If the compressor is running hot and you have no tank and the moisture trap is on the compressor side of the hose rather than the airbrush side, the air will still be hot as it goes through the moisture trap so not as much moisture will be removed... it then cools through the hose itself and condenses in or near the airbrush, causing problems.

But if it weren't for the rise in pressure, simply heating and cooling air back to room temperature shouldn't cause moisture to condense I didn't think. The way dehumidifiers work is to drop temperature below room temperature to remove moisture then heating the air back up again.

By any means I will buy a second moisture trap for the hose of the Airbrush.

I will also place the compressor on the ground and look up for a friend with technical knowledge how to add a Tank to the Compressor so it will not die when I airbrush for more than 20 minutes.

I had kind of the same issue until I bought a In-line moisture trap.

My trap was attached to the compressor and it would spittle out water every few seconds. After changing hoses to have one with a trap near the gun itself, never again have I had water spittle.

As a reference, I use the Master Airbrush series from amazon as the whole kit was fairly cheap and good for learning. Hose was 10-20 bucks I think separate

I did buy at first a trap that attached to the gun itself and then the hose, but that was horrible. It was leakly so ruined the pressure and didn't help much at all.

str00dles1 wrote:
I had kind of the same issue until I bought a In-line moisture trap.

My trap was attached to the compressor and it would spittle out water every few seconds. After changing hoses to have one with a trap near the gun itself, never again have I had water spittle.

As a reference, I use the Master Airbrush series from amazon as the whole kit was fairly cheap and good for learning. Hose was 10-20 bucks I think separate

I did buy at first a trap that attached to the gun itself and then the hose, but that was horrible. It was leakly so ruined the pressure and didn't help much at all.

Just to check if we are on the same page. This is the tool I actually need, right?
http://hobbyland.bg/sglobyaemi/aerografi-i-instrumenti/aerografi-i-kompresori/hs-777a-haosheng-s-d-za-pochistvane-na-aerograf-10535.html

And I attached it to the brush and the hose?

 DalinCriid wrote:
I will also place the compressor on the ground and look up for a friend with technical knowledge how to add a Tank to the Compressor so it will not die when I airbrush for more than 20 minutes.

Be cautious hooking up a tank to a compressor that wasn't designed for one. Some tankless compressors only run intermittently as you spray and if they are weak enough that to fill a tank will require them to run constantly for several minutes it may actually cause them to overheat.

My compressor has a little 3L tank (which it came with) if I replaced it with, for example, a 20L tank, sure, once the tank was filled I could spray for longer without the compressor kicking in, but to actually fill the 20L tank in the first place the compressor would have to run non-stop for a long time and would probably burn out before it got there.

The "tanks put less stress on the compressor" statement isn't always true, it depends on the specific compressor and tank setup.

AllSeeingSkink wrote:

 DalinCriid wrote:
I will also place the compressor on the ground and look up for a friend with technical knowledge how to add a Tank to the Compressor so it will not die when I airbrush for more than 20 minutes.

Be cautious hooking up a tank to a compressor that wasn't designed for one. Some tankless compressors only run intermittently as you spray and if they are weak enough that to fill a tank will require them to run constantly for several minutes it may actually cause them to overheat.

My compressor has a little 3L tank (which it came with) if I replaced it with, for example, a 20L tank, sure, once the tank was filled I could spray for longer without the compressor kicking in, but to actually fill the 20L tank in the first place the compressor would have to run non-stop for a long time and would probably burn out before it got there.

The "tanks put less stress on the compressor" statement isn't always true, it depends on the specific compressor and tank setup.

I am planning no more than 10L Compressor If I even consider to approach this.
For now it will be only the Moisture trap and maybe buy me Iwata later on.

 DalinCriid wrote:
I am planning no more than 10L Compressor If I even consider to approach this.

Still be cautious, what power rating and pressure cut off is your compressor? Mine is 1/6HP and takes ~1.5 minutes to charge a 3L tank to 60PSI, so if I expanded to a 10L tank it would 5 minutes of constant running. I don't intend to upgrade my tank partly because I don't actually know if my compressor is designed to run non-stop for longer than the 1.5 minutes it currently takes to fill the 3L tank.

AllSeeingSkink wrote:

 DalinCriid wrote:
I am planning no more than 10L Compressor If I even consider to approach this.

Still be cautious, what power rating and pressure cut off is your compressor? Mine is 1/6HP and takes ~1.5 minutes to charge a 3L tank to 60PSI, so if I expanded to a 10L tank it would 5 minutes of constant running. I don't intend to upgrade my tank partly because I don't actually know if my compressor is designed to run non-stop for longer than the 1.5 minutes it currently takes to fill the 3L tank.

I am a technological neanderthal so I better copy paste the stats I found for my compressor from a random site:

Type: Single Cylinder Piston Compressor
Power: 1/6 HP
Speed: 1450/1750 r.p.m
Air output per min./litres: 20~23L/min
Auto stop, start at 3BAR(43psi), stop at 4BAR(57psi)
Pressure adjust range: 0~4BAR
Suitable for airbrush with nozzle: 0.2~1.0MM
Net Weight: 4.80KG

Apologies for necroposting and double posting on my own thread, but I thought it is way better to keep the questions here.

I don't have a second moisture trap yet, but I would like to ask one more thing. Most tutorials suggest PSI ~15, but when I set the compressor to 15 the air outgo is so damn miserable that the paint cannot shoot properly OR the PSI instantly drops to 0. Why this occur?