Spray Booths

Design

MAINTAINING BRIGHTNESS IN PAINT SPRAY BOOTHS

In a vast number of spray booths lighting is inadequately designed.  This observation does not refer to brightness within the booth, (some booths are bright enough) but rather the angle at which the lights reflect is often inadequate.  For the most part painters cannot easily judge the quality of their finishes unless they hold their faces very close, at a shallow angle to the surface, so that they can see the wet edge coming off the spray fan.

We have video-taped many painters who keep their faces close to the surface, but inadvertently turn their spray gun outwards when they get to the end of a stroke.  Each time the gun is angled outwards, most of the paint misses the target altogether, and results in wasted overspray.

In at least one spray booth there were no fixed lamps in the side walls of the booth. Instead, portable explosion-proof lights were suspended from the walls, but no more than 3 ft up from the floor. Several of the fluorescent tubes were missing from the housings, and heavy overspray had collected on many of the tubes that were in good order.  In addition, 55-gallon drums, mixing equipment and large items had been stored in front of the lamps, thus blocking much of the available light.  As a result, the booth was dimly lit and painters could not properly see the underside of surfaces that needed to be coated.

These practices often require them to come back later to repair-coat faulty finishes.  Hence more paint and solvent is used, and these are followed by unnecessary pollution, labor and costs.

As a consequence of poorly designed lighting paint defects that result include dry areas, poor uneven overlaps, applying too heavy a coating, etc.  More importantly, the amount of waste overspray from the poorly angled gun can amount to a significant percentage of the total amount of coating used to paint the part.

In many spray booths the initial brightness is impaired for several reasons:

• Overspray collects on the glass panes.

• Painters sometimes test their spray guns on the walls of the booth and dark paint colors diminish the brightness.

• Fluorescent light are missing from the lamp housings.

Recommendations

• Portable, explosion-proof lights should be made available inside the booth so that the light can be reflected from the surface over a wider range of incident angles, thus allowing the painters to have better control of their application at the time of painting.

• Cover the panels with clear plastic film, such as Mylartm or wipe a thin layer of oil over the glass.

• Apply a water-based white strippable coating to the walls of the booth.

• Lay white fire retardant paper on the floor of the booth.  This is especially useful when low level lighting is required.

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