Keeping your spray gun clean can help you achieve high-quality results

It can be said that keeping your spray gun clean is the best thing you can do for your next paint job. With the price of spray guns climbing to $500 and $600 each, keeping them in good operating condition is more important than ever.

Also, the days of pouring a quart of cheap thinner into a spray gun, sloshing it around, and with trigger pulled back flushing it several times while spraying it into the shop for cleaning is no longer practical; and in the face of the new 6H law, such actions are illegal. It's a wise idea to look at the need to comply with the laws and how to do so. Let's look at how to efficiently clean the guns that we use, keeping them in good working order for years to come.

Many years ago when I was a young apprentice, I watched my mentor carefully clean his gun after each use. He would make sure that it was spotless, both inside and out, carefully drying it with a shop towel after he was through. He would then lubricate it and hang it in its specific spot. Each Friday after the work was done, he would disassemble each gun and soak it, and carefully clean each individual part (Fig 1).

He would roll the needle like a pool stick to make sure there was no warp, inspect its tip for wear and place it to the side as he looked carefully at the springs, nozzle and cap. He would hold the cap up to the light, looking through each individual small hole to make sure that no debris was lodged inside.

If debris was found, he would reach for a wooden toothpick, using it to clean each hole carefully, making sure that no damage was done to the cap. When he was sure everything was clean, he would lubricate it, including a small amount of Vaseline on the needle spring. Then he would reassemble it and hang it in its place for the long weekend.

As a young apprentice, I thought that this procedure was a little bit of overkill. Couldn't he just rinse and wipe it like the rest of the painters that I knew? But old Howard was a funny duck, and I just chalked it up to his personality. Each time Howard would teach me something new, he would first demonstrate it, then hand his gun to me and expect me to duplicate it. His gun worked flawlessly. In fact, I took it for granted that all guns worked perfectly under all conditions.

It wasn't until I left my apprenticeship and started painting on my own – and neglected the meticulous cleaning that I had been taught – that I realized that guns not properly cleaned and cared for quickly quit performing well.

You see, as a young painter I was always looking ahead to the next paint job, thinking, "How can I do this faster?" and "Isn't all this cleaning just an old man's way of wasting time at the end of a workday?"

But like many things in the workplace that don't look as if they directly affect cycle time, cleaning your gun is probably the best time spent to speed up your next paint job. By the way, when I left my apprenticeship, my mentor gave me his Binks 62 spray gun, which at that time was several years old and had been rebuilt a couple of times – but was still operating as if it just come out of the box.

Impact of new laws

In January 2008, the U.S. EPA signed into law a new mandate known as the "paint stripping and miscellaneous surface coating area source rule" (40CFR Part63 subpart HHHHHH), commonly known as "rule 6H." The intent of the law is to reduce emissions of certain hazardous air pollutants (HAPs) from a spray application of coatings and from paint stripping.

The 6H rule mandates such things as high-efficiency spray techniques, MeCL paint-stripping activities, technician training and recordkeeping. But what most concerns us here are the restrictions that 6H places on the cleaning of guns.

The rule reads: "Spray Gun Cleaning: All spray gun cleaning must be done in such a way as to avoid the release of solvent and residual paint mists into the air. Never spray cleaning solvent through the spray gun outside of a fully enclosed spray gun washer. Proper cleaning methods include:

• use of a fully-enclosed spray gun washer;
• hand cleaning of disassembled parts; and
• flushing cleaning solvent through the spray gun without pressurizing with air."

That means that to comply with the 6H rule, you must either clean your gun in a fully enclosed spray gun cleaner (Fig 2); hand clean the disassembled parts (Fig 3); or flush clean, as long as the gun is not pressurized (Fig 4). You will notice that the law says specifically "avoid the release of solvent and residual paint mist into the air." This indicates that even with waterborne paint, in which water has significantly, but not completely, replaced solvent as the reducer in the paint, the paint mist would still be released into the atmosphere, and so waterborne gun cleaning is included under the law.

Cleaning in a fully-enclosed gun cleaner (Fig 5) is probably the most commonly used method in a production shop, although some believe that spray gun cleaners do not clean a gun properly. That argument is for another arena; what we will do here is take you through the steps of cleaning with a gun washer. The methods outlined below are not the only way to use a gun cleaner, but serve as an outline of the steps involved.

1. Remove the paint cup from the gun and discard in the appropriate waste disposal container. (Fig 6)

2. While holding the trigger in the fully open position, rinse any residual paint/clear through the gun. (Fig 7)

3. Using the provided tool, clamp the trigger can fully open so as the gun cleaner operates, solvent will be flushed through the paint passages.

Note in Figure 8 that not only does the gun washing tool hold the trigger open, but it also blocks off the air inlet to keep solvent from getting in the passages where it should not go. This step (the blocking of the air intake) is often neglected, and in fact it is why some technicians refer to gun cleaners as "gun ruiners." If solvent gets into the wrong passage (in Fig 9, the blue areas), it can migrate to areas where it comes in contact with bushings and O-rings, which it can eventually deteriorate.

The gun becomes less and less efficient, spraying poorly, and because the onset is slow, it is not always realized that it is solvent damage causing the problem. To rectify ruined bushings, gaskets and O-rings the gun will need to be rebuilt.

4. The gun is then placed in the machine on its proper stand (See Fig 2), and the gun-washing cycle is started. Most gun washers have a timer that allows them to run for a set time.

5. When the gun-washing time has elapsed, take the gun out. Remove the cap and inspect for any debris or wear.

6. The gun is removed from the gun cleaner, dried with a clean cloth and reassembled for its next use.

Non-pressurized gun washing

It is permissible under the regulation to use reduced air and non-pressurized flushing (Fig. 10).

1. Excess paint/clear is poured from the gun into the appropriate disposal or recycle area.

2. Using a squirt bottle, solvent is flushed around the inside of the cup (if using a conventional cup) while the trigger is pulled and enough solvent is flushed through the gun until the stream runs clear.

3. Using the squirt bottle, flush off the exterior of the gun and wipe with a towel.

4. Remove the cap and inspect for paint residue. If any remains, re-flush the gun.

5. When the gun is clean, use compressed air to dry the gun, and store it for next use.

One disadvantage of this type of cleaning is that it requires a relatively large amount of solvent. Re-using the same solvent a number of times can reduce solvent use. Also, some technicians find that non-pressurized gun flushings do not sufficiently clean the gun, and often it must be disassembled and hand cleaned to remove all the paint residue.

Hand cleaning disassembled parts

Some technicians believe that hand cleaning a spray gun is the best and most efficient way to make sure that the gun is cleaned and prepared for the next paint job. As shown in Figure 1, a gun has been partially disassembled. The needle, nozzle, needle spring and air cap have been removed and placed in a pan with solvent. With the use of cleaning brushes, all the fluid passages are cleaned.

In Figure 9, note the red fluid areas, which are relatively small in comparison to the blue air passages on the inside of the spray gun. The red fluid passages are closely cleaned and inspected for wear. All parts, after cleaning, are inspected and dried before reassembly.

You will notice that no blocking device has been started into the air passage inlet before soaking. Soaking, unlike a gun washer, does not pressurize the solvent, and it does not find its way into the packing area.

A gun can be quickly and thoroughly cleaned using this method. Following the cleaning, the solvent in the pan is stored in an airtight container so it does not continue to gas out in between cleanings. The amount of solvent used is minimal, and when it becomes soiled it can be recycled and reused.

Although 20 percent of all solvent emissions in aftermarket refinishing are vented into the atmosphere during the cleaning process, the three methods listed above significantly reduce that solvent release.

Spray gun lubricating

Thorough gun cleaning removes unwanted paint coatings, but in the process, it also removes lubricant from the gun surfaces. Therefore, following a thorough cleaning, the gun will need to be lubricated according to the gun manufacturer's directions. Not just any oil can be used for a gun lubricant. In fact, many oils contain silicone, which will contaminate paint jobs. Use a manufacturer's recommended lubricant to keep the gun operating smoothly.

A. Put one drop on the needle just outside the needle packing housing, then with the gun facing downward, move the trigger backwards and forwards. Both the movement of the needle and gravity will help get the lubricant to the needle packing.

B. Lubricate the air trigger packing just behind the trigger, again with one or two drops of oil; and then hold the gun so gravity will help pull the oil into the packing as the trigger is moved.

C. A small amount of lubricant is used on the trigger screw (both sides) to help combat corrosion and make the trigger action smooth.

D. The needle spring is lubricated with a slight amount of gun lubricant or Vaseline.

Keeping your gun clean is the single most important thing you can do for your next paint job. And though it may look as if it is time consuming, you will experience a significant loss of time if the paint job goes bad because of a dirty gun. If spray guns are cleaned and maintained properly and rebuilt on a regular basis, they can operate well for many years. Some gun parts are consumables and will need to be replaced. Such things as packing, gaskets, O-rings and even needle and nozzle setups will wear and need to be replaced from time to time.

Careful inspection, cleaning and rebuilding can keep a spray gun in good working condition. By the way, 45 years later, I still have that Binks 62 spray gun that Howard gave me. Although technology has changed and new regulations no longer allow me to use a non-HVLP spray gun, it still works flawlessly.