Air brush problem?

should post it at the airbrush forum, they have a lot of experts there.

LM,

28 psi seems high for an airbrush. I have three different brands and the highest pressure recommended for any of them is 20 psi.

Paint buildup in the tip will cause the problem you describe, ie the pulsing or spitting. Depending on what kind of paint you are spraying, the 1 to 1 and 2 to 1 ratio is generally OK.

If you are spraying lacquer with a low temperature flash point thinner it will dry in the tip. I get this problem with Poly-S water based paint if I do not use a "wetting" agent like clear liquid detergent (a very small amount).

Do you clean your airbrush after every use? I take mine apart after every use. A couple times a year I soak the metal parts in paint remover to get the dried paint out of the hard to reach places.

Are you using a moisture trap? Water, condensed out of the air, can cause spitting.

It has been my experience that most airbrush problems arise from an airbrush that needs cleaning. rangerj

Rangerj is correct, a dirty airbrush is nobodies friend. You might consider putting a tank between the airbrush and compressor. It might help you even out the pressure and flow. A good moisture trap and pressure regulater is a must.

I forget now what it's called, but in addition to the water trap and PSI regulator, I use some of that white, tape-like wrap around the threads of the water trap & air hose, which solved my "spitting" problem by making the attachments airtight.

FRank

i think that 28 psi are just too much.try reducing the air pressure at20 psi.most colours with a 2 to 1 thinning ratio are ok

QUOTE: Originally posted by oldhooker I forget now what it's called, but in addition to the water trap and PSI regulator, I use some of that white, tape-like wrap around the threads of the water trap & air hose, which solved my "spitting" problem by making the attachments airtight. FRank

Is that "tape-like wrap" you mentioned teflon tape? I was just wonderin'. I had considered putting that on my airbrush hose, but for some reason I thought it would make it a little more difficult to remove the hose, and would have to be replaced every time you airbrushed. However, I'm probably wrong.

Hi guys,
I have a question to rangerj. In what kind of paint remover do you soke your parts in, "a few times a year"?
Thanks.

T-34,

I have been using Poly-S Paint and Decal Remover. Inbetween paint jobs I soak the metal parts in laquer thinner. In between colors I clean the tip and needle with laquer thinner or denatured alchohol, depending on what kind of paint I am shooting.

If at all possible I plan the painting so that I spray the colors from the lightest to the darkest.

I know this is more than you asked, but I thought others might be interested in what works for me. Actually, I get the ideas from FSM and other written sources on airbrushing. Cheers, rangerj

Is there an alternitive for laqer. If there is can you tell me what.
Thanks

QUOTE: Originally posted by rangerj LM, 28 psi seems high for an airbrush. I have three different brands and the highest pressure recommended for any of them is 20 psi.

Are you talking about the highest pressure recommended for model painting or how much pressure the airbrush can handle?
I have sprayed with my airbrush at 60-80 psi with no problems, although not for model painting. Some airbrush artists spray at almost 100 psi.
The airbrush can take as much pressure as can safely be handled by the airhose.

Mike

love model
I agree with the majority of the other guys, think you are using to high a pressure. You can get a good coat of paint applied but I think you will find that you get better coverage using a lower pressure and have a heck of a lot less overspray. I usually shoot my enamels at 10 to 12 lbs. On your pulsing problem, you didn't say what type of compressor you were using but I would bet that you are using one of the small diaphragm air compressors with a regulator between the compressor and airbrush. Each time the compressor goes thru a cycle (suck air in at bottom of cycle, compress air at middle of cycle and then blow air out at top of cycle) you will get a surge of air. The shorter the air hose, the sharper the surge. If this is the system you are using, then I agree with Woody, you need to get a reservoir in the line. Check your local auto suppy stores for a portable air tank (the kind you fill and take to the car to fill a tire). You should be able to find one for $20 or less. Think that may cure the problem.

Mike,

Yes I am talking about airbrushes made for, and used for, modeling. I have other airbrushes that are used for other purposes that can be sprayed in the higher pressure ranges. Pressure is only one of a combination of factors determined by what you are spraying, the conditions you are spraying in, the coverage you want, the type of finish (e.g. textured or glasslike), etc. The pressure must be considered in combination with the air-flow volume (Standard Cubic Feet per Minute). You match this to the material you are spraying and how thick or thin you are spraying it.

For example, if you spray at 60psi and 5 SCFM a lacquer that is thinned with thinner that has a 60 degree to 70 degree "flash point", at room temperature (72 degrees F) and low humidity (conditions), the paint if sprayed at 12 to 15 inches from the surface will be powder before it hits the surface. Lower the pressure to , say 35 lbs, and the results will be a nice smooth finish.

Without going into the physics of spraying coatings, sufice it to say that most airbrushes made for painting models (aircraft, armour, cars, etc) work well at 15 to 30 psi and relatively low SCFM. But, if 100 psi works for you, by all means do what works best for you I would not argue with sucess.

For many environmental and health reasons the trend in spray painting is, high volume, low pressure (HVLP). Lacquers and enamels are becoming more dificult to get, and the effort is to replace them with "water-based" paints. So, I do not disagree with you Mike. I'm just saying it depends on what yoou are spraying, what you are using, the conditions, and what kind of finish you want. I do push the pressure up when I spray Poly-S because it is a heavier bodied paint, and it needs more pressure and more volume to be properly atomized for the finish I want.

T-34
There are alternatives to lacquer. Are you looking for an alternative solvent/thinner, or alternative coating material, such as acrylic enamel, urithane, or latex.

Denatured alchohol is a good substitute for cleaning, as is acetone. They have their drawbacks, such as being highly flamable and can irritate the skin and LUNGS.
Lastly guys, if what you do works - keep doing it! If it does not work, try something else. rangerj

I would agree with you rangerj.

I had just misunderstood and thought you meant the airbrush could not handle that much pressure. By the way, for Model Master enamels I spray at about 12-18 psi. The 100 psi I mentioned is what some T-shirt airbrush artists spray their water-based acrylics at. The reason for the high pressure is great atomization and the paint penetrates the fabric much better as well as making the paint job faster by conserving strokes.
I personally spray T-shirts at 60 psi.

Take care my friend

Mike