Are HVLP spray guns the final answer to paint over spray?
If you believe much of the marketing hype and even regulatory data many observers can be misled into believing that HVLP spray guns have virtually no paint over spray, are a brilliant new paint spray gun technology, and surpass any other type of spray gun technology that is available.
In truth HVLP claims in relation to over spray are actually based on measurable transfer efficiency. To properly measure transfer efficiency for a spray gun, testing usually needs to be carried out in a laboratory, and an article that is to be spray painted is weighed prior to spray-painting, the amount of paint that is to be placed into the spray gun is also weighed prior to spraying and then the article is spray painted.
After spray painting any remaining paint is weighed and the article that has just been spray painted is weighed once again.
Subtract the original weight of the article prior to spray-painting from the increased weight after spray painting. This will determine the weight of actual paint that has been deposited onto the article.
Next subtract the original weight of the paint prior to spray-painting from the lower weight of the remaining unsprayed paint. This will determine how much paint was actually sprayed.
Now from the figure determined from the difference in paint subtract the difference in the weight of the spray painted article. Now calculate the difference as a percentage to determine transfer efficiency. Of course this method does not account for solvent which evaporates through drying or curing.
The actual transfer efficiency percentage differences can vary on a large scale dependent on other factors such as the spray gun operator technique, the type of paint or coating that is sprayed and even the quality or condition of the actual spray gun. An incorrectly set up HVLP spray gun will generate much more over spray than a correctly set up conventional spray gun. A difficult to atomise paint can generate much more over spray in HVLP spray gun than an easily atomised paint that is applied using a conventional spray gun.
HVLP spray guns are not a guarantee of less paint over spray and very few spray painting industry professionals would argue that HVLP is the best paint finishing spray gun compared to other spray gun designs.
Other types of spray gun technologies that are able to equal or even surpass transfer efficiencies available from using HVLP spray guns includes LVLP spray guns, air assisted airless spray painting and electrostatic spray-painting. Even a correctly setup and operated conventional spray gun can usually exceed the transfer efficiencies of a poorly set up or operated HVLP spray gun.