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Adjusting Air Pressure


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Guys,

Could we once and for all put this issue to rest? Here is the eternal question:

Regardless of airbrush type and air source, What is the correct way to adjust air pressure?

Should we adjust the pressure (with regulator), while pressing the trigger(dynamic) or before pressing it(static)?

There are tons of different ideas online. I personally adjust the pressure while pressing the trigger. Who is with me?

I use Paasche VL airbrush and Paasche D500R.

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Guys,

Could we once and for all put this issue to rest? Here is the eternal question:

Regardless of airbrush type and air source, What is the correct way to adjust air pressure?

Should we adjust the pressure (with regulator), while pressing the trigger(dynamic) or before pressing it(static)?

There are tons of different ideas online. I personally adjust the pressure while pressing the trigger. Who is with me?

I use Paasche VL airbrush and Paasche D500R.

I agree. On one of my compressors, the flowing pressure is about 14 psi if the static pressure is about 22 psi. On another compressor which is bigger, I only need the static pressure to be about 18 psi to get a flowing pressure of 14 psi. The static pressure, therefore, is meaningless because it's so variable.

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While I too agree with the dynamic method in principle, I don't understand why this is important. Adjust the pressure so that your airbrush works properly to suit your style, the viscosity of the medium, the type of airbrush, etc. There are so many other variables at play that knowing the exact pressure you are spraying at is not all that important.

I remember attending a demonstration by an airbrush professional and when he was asked what pressure he was spraying at, he said he didn't know and had to check the gauge to answer the question.

Edited by wdw
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The actual way pressure is measured is at the inlet to the gun or airbrush with maximum airflow only ... no material. With airbrushes and conventional guns, pressure at the cap should be about equal. This does not apply to HVLP guns like the LPH-50 or LPH-80 mini guns from Iwata. Measuring pressure at the tank will be useful to each on an individual basis for personal consistency, but has little meaning in absolute terms because pressure at the airbrush will be effected by things like hose length, diameter, and diameter of the fittings. For those that are interested, I'm going through this on one of the four airbrushing videos that I should have up in the next couple of weeks. I'll also be adding them to my airbrushing page ...

airbrushing_header3.jpg

http://paulbudzik.com/tools-techniques/Airbrushing/airbrushing_for_modelers.html

Paul

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Pressure gauge readings are ball park only. Airbrush artists tweak pressure to get the results they want. Many use a MAC valve, which is like a little faucet that's on or next to the airbrush. With these, you have no idea what the actual pressure is at the head of the airbrush. Pressure settings may matter with a spray gun, but with an airbrush, results are what counts. It's a silly argument. Being able to adjust that pressure and maintain it is what is important.

Don

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Pressure gauge readings are ball park only. Airbrush artists tweak pressure to get the results they want. Many use a MAC valve, which is like a little faucet that's on or next to the airbrush. With these, you have no idea what the actual pressure is at the head of the airbrush. Pressure settings may matter with a spray gun, but with an airbrush, results are what counts. It's a silly argument. Being able to adjust that pressure and maintain it is what is important.

Don

:thumbsup:/>

I think people tend to obsess about every detail of airbrushing, since people who are new or have problems get told: "thinning ratio, distance, air pressure" all the time. But it's all more an art that a science. The variables can only be controlled to a certain degree. For example, I start with a very precise thinning ratio, then adjust it until it looks right. The precision is only to insure the same starting point. Same with air pressure, which is different for each airbrush and each brand or type of paint. Distance from surface varies with the airbrush, the pressure, the ambient conditions, and what I'm trying to do. That's why practice is so important. When it's been awhile since I used a particular airbrush, I bring out the paint hulks to refresh my perception.

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"It's a silly argument" ... Don, I wasn't aware that it was an argument. The OP asked the correct way to measure pressure in. I think it is a question that gets asked a lot, and it is even referred to in the literature that comes with some airbrushes. You're right, and as I stated, any individuals number is not very useful to anyone else. Now with guns, the pressure in, isn't maybe useful ... in a commercial application it can cost you a hefty $10k fine if it is set higher than the manufacturers specs ... so while it isn't applicable in a hobby setting, I only point it out to illustrate the reason for, and how, pressure is measured into a spray device. Judging from the emails I'm getting, a pretty fair number of modelers are looking for small detail guns after my video on primer application. Enough so,instead of answering the same questions over and over, one of the videos in that group that I mentioned above will cover the different types of miniature guns and the necessary air supply requirements.

Paul

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Paul -- You're right. It isn't an argument, it was a question, and that was a poor choice of words. But, I've seen it argued many times. Some people make a big deal of how to adjust air pressure. And, as you pointed out, the actual working pressure at the airbrush depends on losses in the system. You say pressure at the cap should be equal. I assume you mean equal to airbrush inlet pressure. I'm not sure that is true. I expect there are internal drops within the airbrush also. With an Aztek airbrush you can vary air flow from a whisper to full blast by pressure on the trigger alone.

The method of setting pressure may be critical for spray guns. I wouldn't know. But, for airbrushes, it's results that count. And the simple answer to the question asked is that it doesn't matter.

Your videos are great.

Don

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Thanks Don,

Airbrushes and conventional spray guns are based more around pressure. So at max air flow (air control all the way open), pressure at the inlet is pretty much equal to the pressure going out, with no material or air restriction. LPH technology is based on volume of air. The pressure going in, is higher than what is going out (Certified Cap pressure is designed to be 10 psi), however, you touched on it in your original post ... LPH guns require a lot of airflow (high CFM) so while pressure is one thing, you need a system that can supply sufficient sustained volume ... even with conventional airbrushes and guns.

And you're right and I understand your frustration, arguments over air pressure can get to be silly.

Paul

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This question keeps coming up because airbrush compressor manufacturers have moved to cheap, poorly designed pressure regulator.

I have been using a "ture diaphram" type pressure regulator that I got from TCP Global years ago on a Paasche DA400 compressor. The DA400 is powerful enough that I can keep constant pressure up to 60 psi with the Iwata Eclipse at full blast (I normally airbrush at the 15-25 psi range). The regulator reading never change more than 0.5 psi from no flow to full flow. In addition to using the true diaphram type regulator, it is also important to install the pressure gauge at the port 90 degrees to the airflow direction.

http://cs.finescale.com/fsm/tools_techniques_and_reference_materials/f/18/t/117469.aspx

Some of the low end Iwata uses a bleed-off type regulator that makes it difficult to adjust for lower pressure. Worse yet, many of the compressor coming from "made-in-China" sources use just a simple screw adjusted orifice as a regulator. Not only it works poorly, the pressure reading is highly fluctuating and not very repeatable. Looking through the 3 ports on the regulator body, you will see a gaping 1/2" hole. I tried one from Ebay for $16. Nice chrome body, but there is no engineering in its design. It does not work as a regulator.

In contrast, you will see a tiny 1/8-3/16" hole down the ports of a true diaphram type regulator. I got my true diaphram regulator from TCP Global for less than $20, but I don't know if they still sell this type of high quality regulator. You can still get a high end regulator from Iwata or Badger, at the cost of $50-80. The pressure reading in airbrushing is for reference only. It allows you to set the airbrush up the same way when using the same paint. The absolute accuracy is not important, but the repeatability is.

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:thumbsup:/>/>/>

I think people tend to obsess about every detail of airbrushing, since people who are new or have problems get told: "thinning ratio, distance, air pressure" all the time. But it's all more an art that a science. The variables can only be controlled to a certain degree. For example, I start with a very precise thinning ratio, then adjust it until it looks right. The precision is only to insure the same starting point. Same with air pressure, which is different for each airbrush and each brand or type of paint. Distance from surface varies with the airbrush, the pressure, the ambient conditions, and what I'm trying to do. That's why practice is so important. When it's been awhile since I used a particular airbrush, I bring out the paint hulks to refresh my perception.

I'm with you, Don. You have to play it by ear. I have two Paasche H airbrushes and a Paasche Talon. The reason I use Paasche? Simple, it's what I started with. I can add, that the two Paasche H's each have their little nuances. There is very little difference, but one H does work a little bit different than the other. They're kinda like cars. No two cars drive the same, even though they are exactly the same year, make, model, color, et.al. I've had F-16 pilots tell me that this is also the case with the F-16's at their base. So, as I started out, play it by ear.

Edited by balls47
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I'm with you, Don. You have to play it by ear. I have two Paasche H airbrushes and a Paasche Talon. The reason I use Paasche? Simple, it's what I started with. I can add, that the two Paasche H's each have their little nuances. There is very little difference, but one H does work a little bit different than the other. They're kinda like cars. No two cars drive the same, even though they are exactly the same year, make, model, color, et.al. I've had F-16 pilots tell me that this is also the case with the F-16's at their base. So, as I started out, play it by ear.

You are getting me confused with my evil twin … (Just kidding, Don!):lol:/>

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TBH I never really "use" the pressure gauge. I have set it once to ~20psi, and with every cup of paint I load into my airbrush I spray a few lines on a piece of paper and give the regulator a little bit of twist in this direction, a little bit in that direction, until the spray pattern looks nice. Since I never ever get the same mix ratio in my paint, this 15s of adjusting is all I need.

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