Paint Spraying Trouble Shooting Guide by William Rice

If you have problems getting your spray gun to produce an acceptable pattern, remember, it may be the operator and not the gun : ) In this guide we will cover, in addition to possible mechanical problems, surface preparation failures, gun control adjustments and technique errors that can create poor performance.

Without belaboring the obvious, lack of cleanliness, which obstructs the normal operation of any part of the gun, is your NUMBER ONE enemy. A few examples will illustrate this point.

PROBLEM 1:  THE GUN WON'T SPRAY. 

Obviously, the gun needs both fluid and air to spray. First, check to make sure there is material in the cup or pressure pot. As basic as this may seem, it does happen. (Like the appliance that doesn't work because of simply not being plugged in to a socket.) Next, check to make sure there is a sufficient air supply to the gun. With a pressure pot this means checking both the fluid and air pressure gauges to make sure they are at the correct settings. Also, check your air hose and fittings for leaks. If product and air are OK, your problem is something interfering with material flow.

What are the reasons material doesn't flow? Plenty.

Remember, most fluids get thicker as temperature drops. When engine oil does, it causes problems starting your car. When coatings get cold, they can be difficult to spray. As they warm up, their viscosity will quickly drop. Always store containers off the ground in rooms with temperatures above 60 Degrees to minimize this problem. If necessary, the material can be thinned to allow spraying. CAUTION: Be careful to always use the recommended solvent (yes, water is a solvent for our waterborne coatings) in the amounts advised. Over thinning or using the wrong solvents can cause other (sometimes serious) spray ability and coating performance problems.

On siphon feed guns, any blockage, even minor, of the fluid pickup tube (such as dried material) will prevent proper fluid flow, resulting in either inadequate material (or no material at all) being delivered to the air cap for atomization. Also, if the tube is loose (or if the vent hole on the top of the cup is blocked) an efficient vacuum can't be created and little or no product will flow. The same thing will occur on a gravity feed gun cup lid if the vent hole is blocked. If you are using a fluid filter at the end of the pick up tube on a siphon gun, inside the cup connector on a gravity feed gun; or, with a pressure feed gun, either on the pressure pot's pickup tube or in the optional paint pipe and filter assembly, check to see if the filter is clogged. Also, with a pressure pot system, the fluid hose can become clogged. If it is, use a suitable solvent to flush it clean. The retaining ring around the air cap may be loose.  Check and tighten if necessary.

The fluid nozzle may be loose or clogged. To check, unscrew the retaining ring from the gun body. Remove the air cap and check the nozzle. If the nozzle is loose, use your supplied gun wrench to tighten it until snug. If it is not loose, carefully unscrew the fluid nozzle and visually check to make sure all air passages are clean. To clean, soak the nozzle in any recommended solvent for a few minutes then lightly scrub with a soft brush. (An soft old toothbrush can be used.)

Then, use a blowgun to force air through all passages until pristine.  DO NOT USE a wire brush, or hard or sharp tools to clean any part of your gun... EVER. Performance of a quality gun is dependent upon the functional maintenance of the fine tolerances engineered into it at the factory.  Scratches to internal air or fluid passages don't help.

PROBLEM 2:  THE SPRAY PATTERN IS DISTORTED OR INCONSISTENT

First, check your cup or pot to see if you are almost out of product. If not, check for dirt or damage in, on or to the air cap, fluid nozzle or fluid needle. Clean the dirt or replace damaged parts.

PROBLEM 3:  THE GUN LEAKS. 

Material coming out from around the air cap indicates a loose retaining ring. From the air cap itself, the cause can be the use of an unmatched set of needle-nozzle-air cap parts. Check to make sure all are the correct size. Mistakes can happen at the factory or replacement parts shipping department. If you have any incorrect sizes, replace them with proper parts.

The fluid nozzle can be loose. Check and tighten if needed. The fluid needle can also be damaged, preventing it from seating properly into the fluid nozzle. Check and replace it if necessary. To remove the fluid needle, first make sure all air is disconnected. Then, turn the control knob all the way out until it comes off. Remove the spring around it; and, gently remove the needle from the gun. If you have already removed the fluid nozzle, you should be able to hold the gun up to the light and see completely through the barrel to the other end. If the chamber does not look completely clean and round, it needs to be cleaned. Use solvent soaking and air as described above. The fluid needle may not be closing properly because of dried paint on the needle. Clean the needle. The packing nut may be worn, or too loose, or set too tight. Replace or adjust accordingly. The needle spring may be missing or broken. Replace with a new spring. Although most unlikely, the fluid needle may be turned in all the way. If so, turn the needle control knob counter clockwise to open it up.

Summary::  Take the time to learn how your gun is constructed. Know where all the parts go. Keep connections tight and all parts properly fitted and adjusted. Know how to properly clean your gun and then KEEP THE GUN, AND ITS AIR AND FLUID SOURCES CLEAN! In everyday experience, 97% of all mechanical problems will be solved quickly and easily by the simple practice of proper equipment cleaning.

Now, we turn to problems relating to proper control adjustment, temperature and humidity adjustment and surface cleanliness.

PROBLEM 4:  THE SURFACE HAS FISH EYES

The surface is contaminated with oil, wax, silicone or any other substance that prevents the coating from free flow out and uniform film formation. Clean the surface as per directions. OR, the product itself has somehow become contaminated with an incompatible solvent, additive or dirty container. Clean the surface. Then clean the pressure pot or cup, add fresh, filtered material and spray again. OR, the air supply has become contaminated. Check filtration systems for proper operation. Clean, repair or replace.

PROBLEM 5:  THE PATTERN IS HEAVY IN THE MIDDLE.  

You may simply not have enough atomizing air pressure. Check and adjust accordingly. The fan holes in the air cap may be clogged, preventing full atomization of material as it exits the air cap. (A similar effect to having the fan control turned completely closed). Clean the air cap. Your fluid needle and nozzle set may be too large for the material. The air cap can't properly atomize the abundance of fluid exiting the nozzle. Check to insure you are using the recommended size set for your gun as described in the appropriate product data sheet.

PROBLEM 6:  THE SURFACE APPEARS COARSE OR LUMPY. 

There is dirt or dust on the surface. Tack Wipe it off.

OR, the material is contaminated. Filter strain or replace it. Clean the surface and spray again.

PROBLEM 7:  THE SURFACE HAS AN "ORANGE PEEL" APPEARANCE. 

This is caused by a combination of inadequate atomizing air or too thick a material. Properly atomized coatings are composed of multiple minute droplets of fluid material, deposited on the surface close enough to each other so that they can easily join together to form a smooth uniform film. When droplets are too large, the flow out phase is uneven, resulting in the peaks and valleys perceived by the eye as "orange peel". Increase the atomizing air pressure or, if necessary, reduce the viscosity of the coating to the point where the gun can atomize the material finely enough, and the orange peel effect will disappear. NOTE: This is where having an air source matched with the volume and pressure requirements of your gun is so important. If the compressor isn't large enough to deliver what your gun needs, you might as well go get a brush or roller.

PROBLEM 8:  THE COATING HAS RUNS AND SAGS. 

You may have over thinned the coating, especially if you used lacquer retarder which dramatically slows evaporation.
OR, the travel speed of your passes is too slow.
OR, you are spraying too close to the surface.
OR, you have your fluid needle open too far.
OR, the surface is too cold.
OR, your fluid pressure is too high.
OR, a combination of the above :-)

PROBLEM 9:  SURFACE BLUSHING. 

This is a cloudy or milky appearance on the sprayed surface. The cause is water contamination either in the form of surface moisture or high air humidity. The moisture contaminates the surface before the solvents have the time to dry. Blushing which appears as a dull surface may also occur in extremely hot temperatures where the coating will dry before it can flow out to full gloss. The remedy is to add 1-3ounces of lacquer retarder per quart of material. In simple terms, this solvent blend bonds to the water molecules and removes them from the surface as it evaporates. We make a retarder if you need one. It is the finest pure retarder available and the price is not as cheap as one of the "blends". Contact us for a quotation.

PROBLEM 10:  MATERIAL COB WEBS AS IT IS SPRAYED.  

The material is too "HOT". Add one to three ounces of lacquer retarder to slow evaporation to the point where normal atomization and flow out can occur.

PROBLEM 11: OVERSPRAY OR FOGGING.

Over atomization of the coating results in droplets so fine that they appear as a mist or fog. Check the air pressure to make sure it is not excessive. Reduce it to eliminate the fog. Also, you may be holding the gun too far from the surface. Getting the gun closer may reduce the overspray.

AFTER SPRAYING:  

Now that you know what to do and how to do it, after you finish your spraying, return any unaltered (no retarder or thinner added) VIVILON coating material left in your pot or cup to the original container for later use. Any altered VIVILON should be stored in a container labeled appropriately with notations of any thinning solvents used and their amounts. Then it's time to clean the gun with the recommended solvent(s) and store your equipment until next time.

GUN CLEANING:

Siphon, Gravity Feed & Hybrid Guns are easy to clean and SHOULD be cleaned after each use. The procedure is to empty the remaining contents as mentioned above. (Remember to FIRST release the air pressure on the hybrid cups). Add about 4ounces of cleaning solvent to the cup.  Swirl it around for a few seconds and empty into your waste solvent container. Then add enough cleaning solvent to the cup to spray for about 30 seconds (usually about 16 ounces for siphon and 12 ounces for gravity feed). Spray the solvent with the fan control closed until the cup is empty. Remove the retaining ring to access the air cap and fluid nozzle.  Place the air cap into a small can and pour enough solvent into that container to cover the air cap completely. While it soaks, gently clean the fluid nozzle and needle area with a soft brush dipped into your solvent container. Then remove the air cap from the solvent and spray air through it. With a clean soft cloth dipped in solvent, wipe the outer gun body until clean. Replace the air cap, tighten the retaining ring and your gun will be ready to spray the next day.

On pressure pot systems, trigger the gun just enough to blow air through the gun before stopping for the day. Disconnect the air. Then, hold the hose above your head to use gravity to help drain the material in the fluid hose back into the pot. Because you have a closed system with no point of entry for air, there is no opportunity for your material to set up. Therefore, you don't have to clean the pot. BUT, you DO NEED to do the basic gun cleaning outlined above, starting with removing the air cap and ending with gun body cleaning.

REMEMBER:

THINK  ●  EXPERIMENT  ●  TEST  ●  ADJUST  ● TEST  ●  PERFECT