FAQ – Spray Gun

Q. My spray gun pattern is not even and seems to be heavier in certain spots. What can I do to prevent this?

A. The first thing you should do is check to see if the problem is caused by the air cap or fluid tip. Follow this simple rule. Give the air cap a half turn. If you notice the heavier spot on the pattern moving in sync with your turn then your air cap needs to be cleaned or replaced. If your pattern does not change then your fluid tip needs cleaning and should be checked for wear and/or replaced.

Q. How do I prevent/reduce the amount of orange peel?

A. There is a misconception that spray guns cause orange peel. The reality is that there are some important factors that cause 95% of the orange peel problems. The first and most common cause is using the incorrect reducer for the current shop temperature. Too fast of a reducer will not allow the paint to stay wet long enough to flow and lay out. Another common cause of orange peel texture is under reducing material. Even if you use the correct reducer but under reduce, then you will have the same problem of the paint drying too fast without proper flow. Finally the other common cause is gun technique. Moving too slow or too fast, too much distance, not enough fluid, all of these can be causes of texture.

Q. What is the difference between a standard gravity-feed gun and an HVLP gravity-feed gun?

A. High Volume Low Pressure (HVLP) is a technology that increases transfer efficiency and reduces overspray as a result of it. The transfer rate of HVLP guns tend to be between 65-70%. This means that you are only “losing” about 30% of the material in your cup. HVLP guns have an exit psi of 4-10psi at the point of exit which is the air cap. You will notice that you will have slower gun passes with an HVLP but in reality you are achieving coverage much faster because your transfer efficiency is so high. You will also notice that you can spray closer to the surface than with a conventional. This gives a much better control feel during the application. Conventional guns are quite the opposite. They will take in about 30-50psi and have almost as much force at the point of exit. This translates into an inferior transfer rate when compared to an HVLP. Conventional spray guns have a transfer rate of about 25-40%. The high psi at the cap is what causes the large clouds of overspray which is typically about 60-75% of the paint material in your cup. The higher transfer efficiency rate means a savings of material and money.

Q. What does CFM and PSI mean?

A. CFM (cubic feet per minute) rating is the most important factor in selecting a spray gun or compressor so that both can function together properly. PSI (pounds per square inch) is the term for the measurement air pressure. In order for a gun to spray and maintain proper airflow you need to have the appropriate amount of CFM while maintaining adequate PSI. All guns will have a CFM requirement that must be met by the compressor. If not you will not be able to provide enough air to either atomize your paint properly or provide enough air to complete your project without interruption. If your compressor provides less CFM than required for a gun then you will be able to spray fine for a small amount of time before you run out of air and your gun will begin to lose pressure and show the effects (poor atomization, spitting, streaming).

Q. My gun seems to allow air from the fluid tip to escape while my trigger is closed. How do I prevent this?

A. The most common problem for this is usually found in the air valve. Air valves are usually composed of seals and packings as well. With use, small amounts of solvents can produce wear and cause these items to not sit properly, thus not allowing opening and closing off of air distribution properly. The best fix is replacing it with a complete air valve kit when available.

Q. My gun keeps dripping fluid when I close my trigger. Why?

A. The biggest cause of this problem is the needle not sitting properly once the trigger is released. This can be either a small particle floating in the fluid tip or a small build up of material on your needle tip. This will keep the needle from sitting all the way into the fluid tip. You will also want to check to see if your fluid tip is worn and needs replacing. This will happen with time as the needle repeatedly hits the fluid tip during normal operation.

Q. Why can’t I go as fast with my HVLP than I used to with my conventional?

A. You will notice that you will have slower gun passes with an HVLP but in reality you are achieving coverage much faster because your transfer efficiency is so high. You will also notice that you can spray closer to the surface than with a conventional. This gives a much better control feel during the application. Now if you increase the distance between gun and surface you will need to go slower and you may also your fluid might need to increase for the paint to flow. If you are closer then you will need to move quicker and make sure your fluid is set according so that your may avoid too much concentration of fluid as you are moving down the panel. Too much fluid in spots ends up as sags and runs.

Q. Is soaking in solvent the best and easiest way to clean my gun?

A. No it is not. This will give you the appearance of a clean gun on the outside but in reality you are slowly creating a problem in the inside. Gun washers are the optimum cleaning system to be used. This allows solvent to flow through the fluid passages without exposing other sensitive pieces of the gun to solvent (mainly packings and seals). If you soak a gun you are not only allowing solvent to affect all seals and packings but you are allowing contaminated solvent to end up in all areas of the gun. This contaminates will eventually dry and remain in areas not seen by the eye and will begin to effect your application. If a gunwasher is not available then using an airbrush cleaning kit and taking your gun apart is much better alternative than soaking a gun.

Q. I have heard of turbine HVLP. Where would I use that?

A. A turbine is great alternative for compressed air where the ability to be mobile is huge factor. A turbine actually redirects air through the motor and through your hose to your gun. The electric motor allows you to plug it in to an electrical outlet. This is perfect for the painter who does a lot of interior work in different locations. Cabinets, doors, home, industrial and even mobile auto touch up and bumper repair are perfect applications for turbine systems. A big advantage of turbines is the fact that they will run continuously for long periods of time without the worry of running out of air.

Q. Will a turbine spray automotive paint as well?

A. Yes it will. Turbines are the preferred choice for automotive touch up and bumper repair technicians. The key thing to remember is that turbine air is moisture free and is warmer than compressed air. Turbine air actually gets warmer as the motor runs for longer periods of time. This is very important because the slightly warmer air will make your paint flash a little quicker. A few quick adjustments in reducer will solve that problem for you. In all applications it is recommended to keep the turbine away from the overspray as this will dirty your filters and restrict airflow.