Environmental considerations for Paint Spray Gun Cleaning

Paint thinner and solvents are commonly used to clean paint guns because of their ability to dissolve paint residue, especially in the small openings of paint guns. The current shop practice is to use solvents in an enclosed automatic gun washer, manually clean the guns, or to use a combination of both manual and automatic cleaning.

Why Be Concerned About Paint Gun Cleaning Solvent Logo Solvents?
Paint thinner and solvents are effective for cleaning, but there are significant environmental and health concerns related to their use.
  • Solvents contain toxic compounds that present health risks to workers and the community;
  • Volatile Organic Compounds (VOC) emissions from solvents contribute to smog formation;
  • Emissions are strictly regulated by air districts. Shop operators need to know and follow rules for record keeping, purchase, use, storage, and management of solvent products and resulting waste;
  • Paint thinner and acetone are flammable. There may be special requirements or restrictions from local fire departments for the storage and recycling of thinner;
  • Waste thinner and solvents are hazardous waste. Shop owners are responsible for proper management and disposal or recycling, and have potential future liability. There are also cost concerns. Solvent loss from evaporation results in adding make-up solvent and increases costs.
Pollution Prevention Strategies
There are four pollution prevention strategies for spray gun cleaning:
  • Clean with enclosed automatic paint gun washing equipment
  • Extend the effective life of the cleaning solvent with three stage cleaning,
  • Use alternative gun cleaning technology
  • Use disposable paint cup liners

Enclosed Automatic Paint Gun Washers 

S10A With Filtration

Use of an enclosed automatic gun washer can minimize solvent evaporation loss, and reduce worker exposure. An enclosed automatic gun washing system flushes solvent through the paint equipment to remove paint residue. Unfortunately, most Automatic spray gun washers do not clean the spray gun completely, requiring manual cleaning. Systems with both Manual/Automatic cleaning are the best to achieve improved results.  Typically, these units reuse the same solvent over and over creating less than desirable results.  Units that have a filtration system will extend the life of the cleaning solution and provide a better cleaning results.  

To reduce evaporation losses, make sure the equipment is operating properly. For example, check automatic venting systems to ensure that the fan operates only when open, not continuously

Three-stage Cleaning w/ Spray Gun Cleaner – Here is a video showing the process –

Three stage cleaning is a no-cost practice used to extend the life and effectiveness of the cleaning solvent.
  • First Stage Empty: empty the paint cup/container as much as possible, then:
  • Second stage Used” Solventclean paint cup/container and spray gun with used solvent.
  • Third stage “Clean” Solventrinse paint equipment removing the liquefied residues from the First stage.
When the “Clean” solvent runs out, replace the solvent with fresh solvent and distillation recycle the waste solvent. Recycling can also be done with filtration to extend the life of the solvent.. This system can be used with a manualautomatic, or combination of both.Pre-rinsing the paint cup/container prior to the second stage reduces the amount of paint waste entering the gun washerThis will maximize the life of the solvent. 

Alternative Cleaning Technology
This spray gun cleaning technology uses low vapor pressure, low toxicity paint gun cleaning solutions that can clean as well as commonly used thinners and solvents. The spray gun cleaning equipment circulates the cleaning solution through filters to remove paint solids. There are two main types of alternative cleaning solutions currently available, one is water based using glycol, and the other is citrus based, containing d-limonene.

  • The water based/glycol alternative is currently being used in commercial auto body and paint shops. Even though it is water based, it does contain regulatedVOCs. It works by lifting paint from the spray gun surfaces like a stripper, rather than dissolving it. The system recirculates the solution through filters to remove paint solids. This keeps the solution cleaning effectively for extended periods of time. Make-up solution will be needed, but not complete replacement of the solution, reducing product and waste disposal costs. It is not necessary to pre-clean paint pots before putting them in the cleaner, but this will limit the filter life.. The water based solution can be used to clean waterborne coatings as well as solvent based coatings. It is not recommended to do solvent and waterborne products at the same time! Each has a different level of water added for the best performance.
  • The citrus based cleaning system uses a solution containing d-Limonene, produced from citrus products. Cleaning solution is flushed through the paint gun in a similar way to other automatic paint gun cleaners. The cleaning unit is equipped with continuous filtration to remove paint solids and refresh the cleaning solution. Heavily soiled paint guns and cups should be pre-cleaned to conserve the cleaning solution. Replacement of the solution will vary depending on use, on average once or twice each year. The d-Limonene solution can be used to clean solvent based coatings. It does not work as well with waterborne coatings because the paint does not separate well from the cleaning solution and becomes less effective with repeated use..

Disposable Paint Cup Liners

This system has its pluses and its minuses. The plus is the amount of solvent needed to clean equipment can be greatly reduced by using disposable paint gun liners. Most of the solvent used for spray equipment cleaning is used to remove residual coating from the paint cup. If paint cup liners are used, the residual coating dries in the liner, and is disposed of properly. This eliminates the need to clean the paint cup. The minus is that there is limited savings if you are already using a spray gun cleaner system because you still have to clean the spray gun. It will reduce the paint solids and extend the life of the solvent. If you do not have a proper spray gun cleaner then you are cleaning manually with a Ketchup bottle that does not have the proper tools to effectively clean a spray gun. Then there is the biggest problem …….. all of these cups will end up in a landfill or as additional hazardous waste.
Before selecting your environmental process, you should consider the following:
  • What are the local environmental requirements?
  • What cleaning solutions meets your cleaning needs and environmental requirements?
    • Select a solution that cleans effectively and does not evaporate quickly; dry equipment after cleaning with a lint free cloth or compressed air.
    • Alternative cleaning solvents described above are not exempt solvents. They may contribute to smog formation and are not allowed by some air districts
    • Solvents left over from previous gun cleaning practices must be managed appropriately, including solvents reclaimed in an on-site recycler
  • What equipment will provide the best cleaning tools and meet local environmental requirements?
    • Filters and spent solution may need to be disposed of as hazardous waste or tested to determine if they are hazardous;
Unfortunately, many cleaning systems are not used because of various issues. The number one is they do not clean! Make  sure to select a system that cleans the spray gun and meets local environmental requirements.
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