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![]() For Harder & Steenbeck owners: I saw a videoby Pro-Modellerthat showed that the trigger can stick if the air valve assembly is tootight. You might want to watch it. Bubbles in the paint cup This seems to be the most common problem people have with their airbrush. It shows up regularly on the forums I monitor. First,make sure the head assembly isn't loose. Snug it up, butdon'tover-tighten or you might strip the threads. If that doesn'tdoit, then consider this. The only way bubbles can happen isifthere is aleakage from the air path to the paint path. Now lookclosely at your airbrush. If you have the type with afloating nozzle (aka tip), there is no gasket between it and the mainbody of the brush. In the photo on the right, the arrowspoint tothe surfaces where the parts mate. Paint flows inside thenozzleand airflows on the outside. The only thing keeping them apart isthe metal to metal seal. This seal is only good if both thenozzle body and the hole it fits into are perfectly round and dirtfree. One way to see if there is a problem here is to rub alittle bees wax on this part of the nozzle and see if the bubbles goaway. If they do, you may need a new nozzle. If your airbrush has a screw-in nozzle like the one on the right, you may have agasket, possibly made of Teflon, to seal off the nozzle to bodyjoint. You didn’t lose the gasket did you? Overtime, these gaskets can be compressed enough that they leak. This is an easy fix. Just replace the gasket. I've also found that a little lip balm, like Chapstick, on the threads can solve the problem. If you have a tiny screw-in nozzle like the Iwata HP-CR on the right, you may need some sealant like bees wax or lip balm on the threads. Be extremely careful not to over tighten it. The only other place that air can get into the paint path is at the tipof the nozzle, like when you back flush by holding your finger or apaper towel against it. A tiny crack in the end of the tip cancause bubbles. Check it closely with a magnifying glass. I’ve read that paint build-up canoccur here and also cause bubbles. I’ve never seen this, but it'sworth checking for. In order to create a vacuum to pull paint out of the brush, the nozzle has to protrude just a tiny bit past the front of the spray regulator. If it doesn't, you can get pressure instead of a vacuum here and air will blow back into the cup or bottle. This can be a problem in airbrushes with rubber O-rings in the head assembly. Intermittent spraying This can be caused by the same things listed above for bubbles inthe cup. For a siphon fed brush, it can also be caused by a wornneedle bearing or seal. See my page on replacingthe needle bearing forthis. Make sure it isn’t a paint problem. Continuous Paint A common problem is that paint will spray as soon as you press the trigger for air, even before pulling back the trigger. This happens because of an imperfect seal between the needle and nozzle. It sometimes doesn't show up at lower air pressures. It can be caused by a small particle of dirt or dried paint in the nozzle, or a needle or nozzle that is not perfectly round. At low pressure, there is not enough vacuum to overcome the paint viscosity and pull it through the small opening. When the pressure is increased, so does the vacuum and paint is expelled. Sometimes, it can be fixed by rotating the needle in the nozzle with slight pressure. Some people apply a little pressure to the back of the needle when they tighten the needle chuck. But, you have to be careful not to damage the nozzle. Soaking the nozzle in a solvent that dissolves dry paint may also help. Another possibility is that the needle seal is too tight for the trigger return spring to fully seat the needle. You may be able to adjust the trigger tension or the needle seal. You should feel a little drag when you install the needle, but it shouldn't take much force. If you have polished the needle, you may have caused it to go out of round. If you have spares, try swapping parts to find the culprit. Air but no paint Maybe your paint is too thick or has lumps. You could try cranking the air pressure up a little to increase the vacuum, or you could see if the problem goes away when you spray plain water or thinner. Sometimes people forget to tighten the needle chuck. They pull back on the trigger, but the needledoesn’t move; easy to fix once you notice it. Sometimes, if the needle is stuck from dried paint, the needle chuck will slip when you pull back the trigger, even though you tightened it. So, check to see that the needle is really moving. Make sure there is a vent hole in the cap of your siphon bottle orpaint cup lid. Otherwise a vacuum will form and stop thepaint from flowing. In a siphon airbrush, a really leaky needle seal or needle bearing can cause this. To check for this, turn the airbrush upside down and put some water in the paint inlet. If it sprays OK in this position, then the seal may be bad. It may be adjustable or it may need to be replaced. Bad spray pattern orspatters Take a close look at the needle and nozzle. A bent needle orcracked nozzle can cause this. Acrylic paints seem to causesome problems. I’ve never used them so I can’t comment. You can feel for a tiny burr on the tip of the needle by running your fingernail lightly along it. Works for a while, then doesn’t I see this once in a while on the forums. The user says the airbrush works fine for a while, but before they can finish, it begins spraying bad or clogging and they have to stop and clean it. They often blame the airbrush. Here’s what I think. An airbrush is made of hard stuff, like metal or hard plastic. It isn’t very likely to change much during a painting session. If it works when you start, it should work till you finish. So, what does that leave? The Paint! I doubt whether anyone sees this problem spraying ink. Paint can dry on the needle during use, especially if it is acrylic, and especially if the user is in the habit of lifting off the air before returning the trigger all the way forward. This is called tip dry, and is a fact of life when using acrylics, and even somewhat with enamels. Some airbrushes are more prone to this than others, but I believe they all have it to some extent. You can use a brush or Q-tip and solvent to remove it or, like many artists, use your fingernails to pick it off. Sometimes a blast of paint on some scrap will remove it. If you watch many airbrush videos, you will see artists doing this often. Another likely cause is lumps in the paint. If you don’t keep your bottles clean, paint can dry around the mouth of the jar. Then, when you stir or shake, little bits can fall into the bottle and end up in your airbrush. An airbrush does not like lumps. Here again, this is more likely with acrylics because of their fast dry times. So, before you blame the airbrush, clean it well, try some fresh paint or ink and see if the problem goes away. Rough finish, orangepeel, overspray, etc. Sorry to tell you this, but it probably isn’t the brush. A roughsandpaper finish can happen if the airbrush is too far away from theobject. The paint droplets partially dry before they hit and pile upon the surface. Orangepeel happens when the paint droplets don't flow together to form asmooth coat. Try slowing down and applying the paint a littleheavier. Runshappen when the paint is applied too heavy, or it's too thin. Thinner paint needs a thinner application. Specklesare sometimes done on purpose to create a textured effect. Then,it's called stippling. It happens when the air pressure is too lowfor the viscosity of the paint. It can also be done by placingsomething in front of the nozzle to bounce the paint particles aroundand scatter them. When thepaint makes a splat, it's called spidering. It happens when thepaint is too thin, the pressure too high, or you are too close. Needlecentering If youlook dead straight on at the front of an airbrush nozzle and pullback on the trigger, you may find that the needle pulls to one side. Some people notice this and think they have a bad airbrush. Not so. Here's the problem. An airbrush needle is only supported at twopoints, the needle seal and the needle chuck. The distance from theseal to the front of the nozzle can be in excess of one inch. Thenozzle diameter is a fraction of a millimeter. That's an awful smalltarget to hit. So, it is common for the needle to end up slightlyoffset. Fortunately, it turns out it doesn't really affect the spraypattern. Unless it is so far off that it binds, it doesn't matter. Whatdoes make a big difference is the centering of the nozzle within thespray regulator. If this is off very much, the pattern will bedistorted. A roughsandpaper finish can happen if the airbrush is too far away from theobject. The paint droplets partially dry before they hit and pile upon the surface. Orangepeel happens when the paint droplets don't flow together to form asmooth coat. Try slowing down and applying the paint a littleheavier. Runshappen when the paint is applied too heavy, or it's too thin. Thinner paint needs a thinner application. Specklesare sometimes done on purpose to create a textured effect. Then,it's called stippling. It happens when the air pressure is too lowfor the viscosity of the paint. It can also be done by placingsomething in front of the nozzle to bounce the paint particles aroundand scatter them. When thepaint makes a splat, it's called spidering. It happens when thepaint is too thin, the pressure too high, or you are too close. Needlecentering If youlook dead straight on at the front of an airbrush nozzle and pullback on the trigger, you may find that the needle pulls to one side. Some people notice this and think they have a bad airbrush. Not so. Here's the problem. An airbrush needle is only supported at twopoints, the needle seal and the needle chuck. The distance from theseal to the front of the nozzle can be in excess of one inch. Thenozzle diameter is a fraction of a millimeter. That's an awful smalltarget to hit. So, it is common for the needle to end up slightlyoffset. Fortunately, it turns out it doesn't really affect the spraypattern. Unless it is so far off that it binds, it doesn't matter. Whatdoes make a big difference is the centering of the nozzle within thespray regulator. If this is off very much, the pattern will bedistorted. ![]() Also, if you’re still stuck, consider contacting the manufacturer ordealer. My only experience is with Badger and Coast Airbrush,and they both have excellent customer support. Feedback I got ane-mail from Alan Houtz about the sticking Iwata trigger. He saidhe was used to removing the needle on his siphon fed brushes even whenthere was some paint in the cup, and never had a problem. Then hegot an Iwata gravity fed Eclipse HP-CS. Without thinking, he didthe same thing and paint leaked back into the air valve and triggerassembly. I guess it made a real mess. He had to completelydismantle the brush and clean with solvent and micro brushes. Hesays there is an internal brass sleeve in the air valve that has to beremoved for cleaning. To remove it he used a Q-tip soaked withthinner. He inserted it in the valve and used a little side pressure toremove the sleeve. After a thorough scrubbing, his trigger hasworked fine ever since. So, I guess the lesson is; don't removethe needle until the cup is rinsed clean. ![]() Comments are closed.
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