Kirby Vacuum’s Unintended Role In Wood Prefinishing

Kirby Vacuum’s Unintended Role In Wood Prefinishing

Bob Flexner, writing for Woodshop News, piqued our interest in HVLP spraying by tying its history to the Kirby vacuum cleaner.  In the 1930s, Kirby vacuums included a spray gun attachment to clean carpets and fabrics.  This gun combined the vacuum’s “high volume of air with very little air pressure”… “to atomize liquids.”

This process grew into the spray process we know today, as HVLP.  According to Flexner, a California government agency coined “the name, ‘high-volume, low-pressure’.”

Inventions create unintended benefits
Jim Kirby, founder of Kirby Co., patented over 200 ideas and inventions.  His place in the vacuum world is secure.  But thanks to Flexner, he is also remembered in the unlikely world of wood finishing (prefinishing, is in a factory setting).

Midwest Prefinishing robotic HVLP sprayer

Midwest Prefinishing robotic HVLP sprayer

TE, HVLP, MnTAP: Acronym Overkill
Kirby’s impact is far-reaching.  It affects the environment and material costs.  And, it’s related to another acronym, TE (transfer efficiency).  TE is a ratio measuring how much finish makes it from the can to the surface.  For example, if one gallon of coating is used to finish an object but only half of the material sprayed actually lands on it, then the TE is 50%.  In the hands of a skilled and trained operator, an HVLP gun can achieve a TE of 70%; in the hands of a novice, 60%.

A lower TE increases waste and environmental problems.  But the most important effect is in the finish itself: it failed to build the specified thickness.  In a 2003 report on Spray Painting and Coating Waste Reduction Alternatives, MnTap (Minnesota Technical Assistance Program) wrote, “More importantly, the overall transfer efficiency of a specific coating refers to the amount of coating needed to get the proper dry film thickness.”

Automated HVLP at Midwest Prefinishing
Midwest Prefinishing operates an automated HVLP spray gun to reduce the overspray cloud and to apply more material to the object.  Its automation removes the element of operator skill, improving the TE ratio even more.  Midwest also recycles 100% of the waste.  Taken together, prefinishing is superior to jobsite finishing in most applications.

Less Paint or Stain, More Savings
The higher the TE, the less paint or stain is required to finish a door.  Plus, it reduces waste and air emissions.  Thanks to some unintended help from Jim Kirby, prefinishing grew, making prefinished doors, mouldings, and millwork more affordable and clean.

Does anyone remember the cleaning attachment on an early Kirby vacuum?  Did it work well?

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