Problems with spraying metallic paints through my airbrush

General Discussions General Painting
,
1

Yesterday I was going to paint the last part of the tracks of the Sd. Kfz. 9 Famo I’ve been working on for so very long now. But, the airbrush problems were back to bully me again. And that’s odd because the session before, everything did go pretty well. Previous session I decided to first test everything thoroughly before starting with my session. Testing was done by first spraying tap water through my airbrush, which didn’t have any problems. It seemed everything was working just fine. The second test was spraying some Tamiya acrylic thinner through my airbrush. And again, everything seemed to be working just fine. And last but not least I sprayed some Mr. Airbrush Cleaner through my airbrush which seemed to be working fine as well.

With the spraying of the Tamiya XF-56 I first did have some problems. With unregular spraying pattern. And I first thought, what if I crank up the pressure? But then I first decided to pull back more on the trigger. Open the paint more. And when I did that. It seemed to be spraying just fine. With of course maintaining a larger distance from the track. I did conclude I could have left the paint a little less open. Just a little. But, I was pretty satisfied with the result overall. I also recognized I made the mistake of wanting to do everything in one go. And that I should have done it in more layers. But it seemed the paint held up pretty well. Even when scratching the paint with my finger nails. Little ammounts of paint came of. Which gave me the impression that the paint was holding up pretty good still. Plus, I had primed the tracks beforehand with Revell Basic Color spray can primer. Which I’m also thinking I want to use up and then try some other primers as well. Spray can or airbrush. Particularly Mr. Hobby primer, because I have read good stories about that stuff.

The next session however, which was yesterday. Assuming would now just be working fine. It didn’t. I mixed up the paint for my airbrush in my Mr. Paint Tray cups. Putting 2 parts paint in, 4 parts thinner and one drop of Tamiya paint Retarder. Which was also the mix ratio I used previous session.

But, this time I had a serious problem. Huge bubbles splattered out of the paint cup. Luckily I did put in first a small amount of paint. Otherwise it would became a mess. But it obviously wasn’t very good. So, I poured the remaining paint out of the paint cup back in the Mr. Paint Tray. And decided to run some thinner through the airbrush. But, still bubbles. And a very unregular spray pattern. Just a sputtering and hissing sound and spray pattern. After that, which didn’t seem to work to solve the problem. I did run some Mr. Airbrush Cleaner through. I decided to first let everything bubble in the paint cup. Like the ‘backflush’ method with blocking the front of with a finger. Except, I didn’t block it of with my finger. I also don’t have a cap for that. And the air cap on the front of my airbrush has also wholes in the sides. Which makes it impossible to block it of with just a finger tip. When I did look in the paint cup. I noticed a lot of metal pigments floating in the Mr. Airbrush Cleaner.

So I did run the airbrush cleaner through my airbrush. And took everything apart. First the nozzle assembly with the aircap, and the other parts. Inspected it by keeping it in light. And everything seemed clean to me. So I did some Mr. Airbrush cleaner in a Mr. Paint tray and did let the nozzle soak in the airbrush cleaner for a few minutes. But nothing seemed to come out of the nozzle. I believe some paint could be on the cleaning brush I cleaned the nozzle with. But that could also be from a previous cleaning session I believe.

Then I pulled the needle out the front of the airbrush. In order to not pull all the dirt and stuff you don’t want in your airbrush through the airbrush body. And dropped it carefully in the Mr. Airbrush cleaner solution. Letting it soak in there for a few minutes. After that, taking it out of the Mr. Airbrush Cleaner and wipe it across a paper towel. Not much if any came on the paper towel in terms of paint or pigment. Even when getting some Mr. Airbrush Cleaner on the paper towel and giving it another wipe. It just looked very clean.

And then I cleaned the paint cup with the paper towel and Mr. Airbrush cleaner on it. Took a cotton swap and also did the area lower of the paint cup. Which did have some paint coming out on the cotton swap. Did this a couple of times until it looked fairly clean.

After that, I did do the exact same thing on the front side of the airbrush. Which also had paint coming of on the cotton swap. I did this also a couple of times. Until that looked fairly clean as well.

With my whole day being ruined. I just tidied everything up. Stored everything away on the place where it belongs. And still having no idea what has happened or did go wrong. As far as I know I did nothing wrong. Apart from not testing beforehand if everything was working properly.

What could be the issue? What should I do next time a problem such as this occurs? What would be good practices to prevent problems like this as much as possible in the future from happening?

2

A couple of things.

  1. did you clean your airbrush between sessions 1 & 2 before you ran into problems? This can usually be done with a run through of thinner at the end of your session until it comes through clear. It sounds to me like you had a blockage somewhere, causing the bubbling you saw in the color cup. This isn’t restricted to Metallics either, you should clean the airbrush every time you are done painting.

  2. tamiya metallics are notoriously tough to spray. Some are better than others, but as you experienced this usually requires high pressure. I boil it down to Tamiya metallics having large metallic particles. I try to avoid them when I can now, but dark iron is too good a color to pass up.

1 Like
3

  1. If I’m remembering correctly, I did a full disassembly of the airbrush when I was done with spraying the previous session. And it looked like everything was perfectly clean. Do you have any tips to check more thoroughly if everything is spotless clean? And what other areas and things should be carefull cleaned as well, other then the needle, paint cup, the reservoir of the paint cup in the airbrush body itself, and the nozzle assembly?

  2. What would be a better acrylic paint brand for spraying metallic colors like for tracks? A brand that doesn’t give as much problems as the Tamiya metallic paints give? Are there any tips or tricks to prevent problems with spraying this particular paint brand colors? Would it be better to just paint them with brushes instead?

I’m currently thinking, let’s use up the Tamiya acrylic metallic paint colors. And try Mr. Hobby for this instead. Would that be a solution to my problem? Or are Mr. Hobby just like or the same as Tamiya acrylic paints? I’m going to do some ordering of my model making stuff and tools. Going to clean out my pipettes and may give my airbrush a thorough inspection as well. If I’m having the time for it.

Thank you for providing the information and the questions to help me further.

4

Air bubbling into the paint cup on the airbrush is a symptom of a compromised air seal (usually around the needle) between the air channels and the paint channels. Basically, compressed air is passing the seal around the needle and entering the paint cup.

A similar symptom occurs with another, less common, problem. This is when compressed air is forced back through the paint tip from the air tip. The air cannot pass normally forward and out of the air brush tip, and some of it is passing back past the tip of the needle into the paint channel that the needle passes through from the paint cup to the paint tip. This is usually caused by improper cleaning. However, depending on the airbrush design, there may be another o-ring located here that could be missing or which is damaged. Sometimes this problem can occur if the airbrush tip parts are not properly assembled allowing air to pass through one of the threaded connections.

The remedy for the first problem is usually replacing the o-ring seal (sometimes called a packing seal or simply an o-ring). Sometimes a thorough cleaning with an application of needle lubricant will resolve the problem, but if the o-ring has been damaged, it will eventually have to be replaced.

Note that this air seal o-ring does wear out over time, and this wear is accelerated if the airbrush is not properly cared for. Most of the damage (If this is the cause of your problem) may have occurred in the past and only some small amount of normal wear was needed for the problem to manifest itself.

The remedies for the second problem are: simply proper cleaning with an emphasis on the air brush tip parts (paint and air tips and the needle); ensuring that the tip parts are properly assembled; ensuring that the tip o-ring (if required) is present and not worn or damaged.

In the end, I think it highly unlikely that air bubbling up in the paint cup is caused by the brand of paint or how it has been thinned. This is basically a mechanical problem with the airbrush.

5

If I’m understanding correctly, I need to inspect my airbrush very thoroughly to find the course of the problem. It could be that something is broken, or there is still some dirt somewhere in the airbrush which needs to be cleaned out.

I’m not reading very clearly on how to do it.

But, what I’am going to do, is when I got time to do it inspect my airbrush properly. Send photo’s of what I can in this thread. And report further with the steps I’ve taken. That way, we are able to exclude more and more causes of possible problems. Getting closer to the actual solution of the problem. As I’m still having a lot to learn about my airbrush.

6

@SdAufKla I took the airbrush apart, but everything looked spotlessly clean. But, I noticed when I wanted to pull the needle out. That it wasn’t going as smoothly as it should be going. When moving it a little bit back and forth. I felled that it wasn’t going out as smoothly as it should be. And sure enough when I pulled out the needle, being very gentle and careful to not bend the needle or cause any damage. There was metallic paint on the needle. On the needle only. So I cleaned that using a paper towel and Mr. Airbrush Cleaner on it. But I’m still not knowing what the cause of the problem is. Everything looks just fine to me. I can see through the whole airbrush. Doesn’t seem to be any paint residue or something in a channel or something where it shouldn’t be to my knowledge. Aircap had a little bit of paint in the very inside of the cap. That has now been cleaned with a cotton swap. What could the problem be? Does this further information help in anyway to help me with solving the problem? I’ve also dissambled the trigger of the airbrush and spring for the trigger of the airbrush. But that seemed fine to me as well. What would you need to further assist me with solving the problem?

When I screwed the Aircap assembly back on the airbrush body. The ring of the air head didn’t feel very warn to me. I felt it touching the airbrush body when screwing it back in place. And it was also the case when unscrewing the air head. However, now I’m wanting to insert the needle back into the airbrush, it seems something is blocking the needle from going in very smoothly. It seems like I have to put some pressure on to get it through to the needle tip.

7

I’m willing to bet the dirty parts you describe cause the issue.

One more question? Does the paint cup only bubble when you pull back on the needle or as soon as you supply air? If it only bubbles when you pull the needle back what’s happening is the airflow is blocked (likely by a dirty airbrush) and when you open the needle, the air takes the path of least resistance flowing back imto the color cup

If it bubbles all the time you probably have a blown seal

1 Like
8

I believe the bubbling starts as soon as I’m supplying air. No matter what fluid I’m blowing through. As soon as I press down on the trigger. It starts bubbling.

9

This is a classic symptom of a compromised seal between the needle and the paint cup and is almost certainly the problem. However…

If is possible for compressed air to be diverted (partially or fully) at the air-paint tip. That is, air is passing the TIP of the needle and then traveling back from the tip into the paint cup.

The way to diagnose between these two different problems is to observe WHEN the bubbling in the paint cup starts.

Does is start when the trigger is pushed down for air BUT BEFORE the trigger is pulled to the rear for paint? This MUST be the air seal before the needle passes through the paint cup (because the tip of the needle is still closing the paint tip - no air can enter through the paint tip).

Does the bubbling start when the trigger is down and AFTER is it pulled to the rear for paint? Air pressure is on but passing out the tip BUT NOT bubbling into the cup, but as soon as the needle is pulled to the rear to open the paint tip, air is passing back into the cup. There is a problem in the air-paint tip. This problem will also make the airbrush paint poorly with a pulsating, irregular paint flow.

Another check is to judge how much the paint in the cup is bubbling. Usually, if the problem is a compromised needle seal then the bubbling is very bad with lots of air coming out of the cup. If the paint bubbles are small and intermittent, then a problem at the paint-air tip is possible.

You can try to apply a very small amount of wax to the needle shaft (a paste wax like used for floor, shoe or car polishing or - better - a lip balm used for chapped lips). If the problem is the needle seal, this may eliminate or mitigate the problem (which then tells you where the issue is).

If this doesn’t help, then try adding a small amount of the same wax to the threads of the paint and air tip nozzles then reassemble them to the airbrush. Again, if this fixes or makes the problem better, that tells you where the problem lies.

I do recall some time ago we had discussions about cleaning airbrushes and at that time you had a problem where your needle was stuck in the airbrush and was very hard to remove. At that time several of us advised you about the proper “to the front” technique to pull your needle out for cleaning. It is possible that before you learned the proper method that you may have damaged the needle seal by pulling a dirty needle through the seal.

Try the lip-balm wax trick to see if that helps or fixes the problem. Be sure to use only a small amount of wax. Just a small bit the size of a pin head and spread along the needle a centimeter or two. Even less on the air and paint tip nozzle threads.

2 Likes
10

I agree with @SdAufKla one further check. Make sure you have the matching needle and tip size. I accidentally put my number 5 needle in my number 3 nozzle yesterday and had bubbling in the paint cup.

1 Like
11

Okay, I’m finally able to reply and provide a update on my airbrush situation.
It seems that my problem is solved, because I have called with the shop where I purchased my airbrush. And did some testing with water running through the airbrush. And no bubbles anymore in the paint cup whatsoever. I did take the airbrush a few times apart in the heat outside, which wasn’t pleasant at all. Even in the shadow. And cleaned everything once again. Everything was spotlessly clean what had to be cleaned after every painting session. On recommendation of the store I cranked the airpressure down right to 1,5 bar instead of 3 bar working pressure. I also did change my mixing of the metallic color I sprayed. With what the store did advice. 2 parts paint and one part thinner. Which also seemed to have done the trick together with cranking down the pressure. How the problem is solved is still a mysterie to me. And how it did occure is even more puzzling me. But, it seems everything is alright again. Not airbrushing anytime soon since I’m working on the figures of my Famo project which take up a long time to do. And a lot of other brush works. So airbrushing will not occur in a very long time. I’am a bit embarrased to give this answer, because it seems I have more ‘mystical’ problems with various things I’m doing not just airbrushing but with computers to. But the most important thing is, I guess that the problem is solved.

12

No need to be embarrassed. I am convinced that there is a certain degree of Voodo Magic associated with air brushing and it’s many attendant problems/difficulties.

2 Likes
13

My guess is that the shop’s suggested change in operating pressure from 3 bar down to 1 bar is what resolved the problem.

3 bar equals almost 45 psi (44.1 psi) which is way, way higher pressure than most of us use for model painting. It is possible that this high pressure was forcing air past the needle packing seal into the paint cup.

I’m generally using pressures around 15-20 psi (~1 - 1.5 bar) and often even lower, maybe down to 10 psi (~.75 bar).

There remains the possibility that your cleaning efforts also removed some bit of dried paint that was causing the issue.

I would still recommend that you make regular use of some sort of needle lubricant. There are proprietary airbrush lubes, but as an expedient, you can use a waxy lip balm (a very spare amount).

14

I’m wondering how it’s working with the holding tank below my compressor where the air goes in. Why does the compressor turn on earlier then other times. And why later sometimes? Does the holding tank have more storage of air if using a high working pressure that it turns on less often? Or is it the other way around? I’m curious to find out.

At Airbrush Services Almere they have some airbrush lubricants. Vasceline and others like badger needle juice. I would not be sure which one to purchase. What would be best for an absolute beginner?

15

The compressor should kick on more at high air pressure. Assuming a constant diameter outlet like we have in airbrush, the rate of airflow (how fast air leaves the tank) is directly proportional to the air pressure.

As air leaves the tank, pressure drops until it reaches a threshold (for my compressor 75 psi) when the compressor kicks back on.

For detail painting around 7-10 psi I can paint for a while without the compressor kicking in. When I am priming it kicks on pretty frequently

16

Any of the proprietary airbrush lubricants are equally suitable for any skill-level user. Just follow the directions or suggested use tips. Badger Needle Juice, Regdab, Iwata Super Lube, etc. are all pretty much the same basic stuff - water soluble products that will wash away with water or alcohol. A wax product like lip balm will also work and not affect the quality of your paint job.

You only need to use a very small amount on the shaft of the needle after cleaning or disassembly. Move back just behind the tapered point and put about a pin-head’s worth of the lubricant on the shaft. Spread it back and along the needle’s shaft for a centimeter or two. Most of it will be wiped off the needle as it is inserted through the packing seal (air seal). You don’t really want any on the tapered point of the needle. It will serve no useful purpose there. A small amount remaining on the needle shaft where it passes through the hole in the trigger over the air valve will help keep things moving smoothly there, too.

No need to use too much since it will just sit inside the body of the airbrush around the needle packing seal. You only need to lubricate the needle where it passes through the packing seal and the mechanical part of the trigger button.

The same stuff can be used around the threads of the airbrush air and paint tip parts where they screw into the airbrush, but again, just the smallest amounts possible. This can help make disassembly easier while keeping paint and compressed air from leaking past the threads. It mostly helps with disassembly and cleaning, tho.

2 Likes