FAQ's

Q. My Siphon/Suction spray gun is spitting, sputtering or blowing bubbles in the cup.
A. Possible solutions:
- Fluid tip is not properly seated into the head of the gun – tighten fluid tip.
- Make sure the air cap is suction/siphon feed type – pressure feed air caps will not spray.
- Check seating surface of fluid tip for scratches or gouges, also check seating surface inside head of gun. Replace if damaged.

Q. My spray gun is spraying heavy to one side of pattern.
A. Possible solutions:
- Rotate air cap 180 degrees and spray a test pattern – this will determine if the heavy is associated with the air cap.
- Dried paint or debris may be in the fluid tip – clean or replace tip.
- Fluid needle has dried paint or debris or needle is bent – clean or replace fluid needle.

Q. What horsepower compressor will I need to operate my spray gun and tank or pump? A. Possible solutions:
- Check your part sheet or service bulletin for the air flow required for the particular spray gun and pump. Pressure tanks consume very little air; however, if an agitator is used with the tank, the agitator air motor can consume 6-10cfm depending on the size and speed at which it is operated.
- When sizing a compressor, you will need to consider the flow and pressure output of the compressor to justify the horsepower requirement. An excellent discussion of this is contained in our Training Bulletin entitled, ‘Compressed Air Supply’.

Q. What fluid tip, needle and air cap would I use to spray a particular product?
A. The best answer is to check the material Product Data Sheet (not the MSDS) to see if the coating manufacturer has tested the sprayability of the material. Often the data sheet will specify the spray equipment and fluid tip and air cap that will work best for the material. Contact Tech Support if additional assistance is required.

Q. What is the difference between Conventional, HVLP, Turbine HVLP and Trans-Tech (LVMP) technologies?
A. Please refer to the following:
- Conventional: Conventional spray guns typically operate at pressures of 40- 60PSI out of the air cap. Atomization is typically better than HVLP and slightly better than Trans-Tech. It is common for the transfer efficiency (percentage of paint solids reaching the parts) t be 50% or less.
- HVLP: High Volume Low Pressure – These guns are considered to be 65% efficient or better and are compliant with the California South Coast Air Quality Management District. The high volume of air exiting the air cap is what helps to atomize the material. The pressure of the air exiting the air cap is 10PSI or less.
- Turbine HVLP: Much the same characteristics as HVLP except that the air source is a turbine. Turbine HVLP guns have the advantage of being more portable than HVLP guns but have the drawback of a large diameter air hose from the turbine to the handle of the gun. The large diameter hose substantially hinders the movement of the spray gun.
- Trans-Tech (LVMP): Trans-Tech spray guns operate on low volume, medium pressures, typically 10-20PSI; transfer efficiencies are typically about 60% or better. Trans-tech technology approaches the finish quality of a conventional spray gun at near the efficiency of HVLP. Trans-Tech is used where compliance is not required but cost savings is important.

Q. I am experiencing orange peel in my finish – my finish is irregular and bumpy with craters.
A. “Orange Peel” can have multiple causes. It happens when the surface of the coating starts to dry before the base paint dries. The main causes are:
- The Coating has been applied too thick which could be due to the fluid tip and needle being too large causing an excess of material to be delivered.
- The material has not been properly atomized. This could be due to insufficient air pressure. The fluid pressure may also be too high which prevents fine atomization.
- The coating viscosity is too thick.
- The spray gun is being held too close to the object being sprayed.
- The weather conditions are too dry, causing the surface to dry too fast. The solution could be to use a slower reducer.


Q. Where can I find out more information regarding spray gun fundamentals, material application, finish problems, and the latest information regarding spray gun technology?
A. Please refer to the following list of publications offered on this web site. The documents are in pdf form and represent the most asked-about questions that our Tech Support team has encountered.
- Coating Materials
- Air Operated Spray Equipment
- Safety Considerations in Paint Applications
- Surface Preparation
- Finish Problems – Solvent Base Coatings
- Compressed Air Spray Gun Principles
- Equipment Selection for the Painting Contractor
- Fundamental of Hand Spray Technique
- Fluid and Air Nozzle Selection
- Viscosity
- Industrial Spray Equipment Selection
- Compressed Air Supply
- Plural Component Spray Systems
- Spray Application Processes
- High Volume Low Pressure – HVLP
- How to Select Spray Equipment
- Air Assisted Airless Spraying
- Airless Spraying
- Operator Techniques
- Hose and Fittings


Q. How does tip wear affect my setup?
A.
- Flow rate increases
- As the tip wears, the physical opening in the tip increases. An increase from .015” to .017” (two one-thousands of an inch) may result in a 33% increase in flow rates. How quickly this happens depends on the factors listed above.
- Pattern size decreases
- The tip will wear out in the top and bottom portions of the tip opening. This will result in a smaller pattern size. It will continue to decrease in size as the tip wears.

Q. How does tip wear affect my spraying?
A.
- Tip wear is gradual, usually over days or weeks. The operator will attempt to compensate by doing the following:
- Increase fluid pressure (an attempt to achieve an acceptable pattern). This will increase fluid delivery even more.
- Back away from the part (an attempt to achieve a larger pattern). This may result in a dryer spray pattern.
- Increase gun speed (an attempt to prevent runs and sags).

Q. How long should a gun last before needing to be rebuilt? What can I do to make it last longer?
A. This depends on what material you're spraying and how many gallons sprayed per day. For example, with lacquers, guns don't need rebuilding as often because lacquers don't have solids in them. In contrast, the high solids in blockfillers are abrasive and require more frequent gun rebuilding. One way to increase gun life before repacking is to thoroughly clean your gun at the end of every day. Be sure to trigger the gun before removing the diffuser and when installing the diffuser. If you don't, the diffuser will score around the ball on the new needle which can lead to premature wear. Your gun will develop a leak and this will cause spitting.

Q. Why is my gun spitting a small paint stream of paint after I release the trigger?
A. The cause of the problem is that the needle is not seating properly in the seat. You will need to either purchase a kit for the gun needle and seat or you may only need to clean the needle and seat assembly. Residue or debris may cause the needle to move off to the side before seating. Tip extensions, extension poles and tip filters can also cause spitting or a stream of fluid after the gun is released due to decompression of the paint trapped between the gun and the tip. Fluid pressure dissipating through the tip causes this spitting or paint stream. An automatic shut-off valve will prevent this problem.

Q. How do I know what size needle and nozzle is best for my application?
A. Although every job may have slightly different requirements, for most materials it is best to choose a mid-size, or No. 3, needle and nozzle. If your paint is thicker than standard oil-based enamel, you may want to consider a larger size. Remember that there is no one tip that is perfect for all jobs. Needles and nozzles are quick and easy to change out. So try different sizes until you find what works best.

Q. What criteria should be known when selecting a Spray Gun?
A. The selection of a spray gun is an important decision to make in the design of a spray system. Matching the gun and fluid source to the application is of utmost importance. Failure to choose the correct equipment generally results in lower efficiencies, increased coating costs, increased emissions, higher booth filter costs, etc.
To match the spray gun to the application, the following criteria must be known:
- Fluid Viscosity
Generally listed as high, medium and low - manufacturers' charts will usually indicate the capabilities of their air caps and fluid nozzles in terms of viscosity. If one knows the viscosity in centipoise or time in a viscosity cup, it is a simple matter of conversion to the criteria listed.
- Fluid Flow
Generally listed in ounces, cc, ml or gallons per minute - spray gun charts will generally indicate a range of flow rates for a given fluid tip / air cap combination.
- Production Rate
Production speed will dictate what the flow rate of the equipment should be. Obviously, a line running a 30 feet per minute with 6 square foot parts will require a higher flow rate than a line moving at 10 feet per minute with 2 square foot parts.
- Available Air (psi & cfm)
In most plants, the available air is adequate to supply the necessary air required by a spray gun.
- Problems usually show up when:
- Restrictive quick disconnects are used
- Small I.D. air hoses are used (i.e.¼”)
- Air hose longer that necessary is being used.
- Compressors too small in size
Keep in mind, a typical industrial air cap consumes 20+ CFM
- Fan Pattern Size
Pattern size is one parameter listed for an air cap. It should be matched to the part being sprayed. Pattern sizes range from as small as one inch to several feet.
- Atomization Required
A “Class A” finish is not required for all applications. Applying a finish to a garden utensil would not necessarily be the same as the hood of an automobile. A stain applied to wood that is to be wiped off would dictate a very low level of atomization. If a lower level of atomization is required, an air cap with a lower CFM ($$$) would be selected.
- Atomization Type
- Air Atomized
* Conventional Air Spray
Conventional air spray is the lowest in efficiency of the different atomization types, but yields good atomization with difficult to atomize coatings. Conventional air spray may not be permitted by Federal, state or local rules for some industries.
* HVLP (High Volume Low Pressure)
An air atomized spray gun with a limit of 10 psi at the air cap. Since there is a legal limit (10 psi) in many cases, choosing the proper air cap for the above criteria is critical.
- Hydraulically Atomized
* Airless Uses high fluid pressure (1000-5000 psi) to atomize. Capable of very high flow rates, lower in atomization capabilities than air atomized equipment.
* Air Assist Airless
Uses high fluid pressure (300-1500 psi) to atomize. At these lower pressures (compared to airless) the top and bottom of the pattern have a difficult time atomizing. An air cap is added for the sole purpose of eliminating the “tails”. Quality of finish is between air atomized and airless guns.
- Fluid Delivery System
- Suction Feed
Suction feed guns have been around for a century. While they are simple to operate, they are the most inefficient of the group. The range of motion is somewhat restricted since the pick-up tube must remain in the fluid to function. It is available in conventional air spray and HVLP. - Gravity Feed Gravity feed guns depend on gravity (cup is on top) to supply fluid to the gun. As a result, some control of the gun is gained over suction feed. Maximum use of the material due to gravity is also a plus. - Pressure Feed Allows maximum control of the required pressures (air and fluid). The source of the coating is dependent on the amount used during a given time period. Available sources include pressurized attached cups, pressure pots (.5 to 60 gallons) and pumps (both low and high pressure) - Given the above criteria, a competent equipment supplier can match the equipment to the application.