Lighting for the Spray Room

Artificial light needs to be bright, good quality, and at the right angle. August 9, 2005

Question
I am setting up a spray room that is 12x12 with white walls, and I am looking for some recommendations on what type of lighting to install. I build Wood Interior Shutters, and I spray HVLP and the panels are assembled and not in pieces. I was using overhead fluorescents, but for the life of me I cannot see my waterbourne Polyurethanes (clears) going on until it’s too late – there is too much reflection.

I have tried to lower the watts and placement to no avail. Should I switch to Halogen Floods (hot) or daisy chain wire some incandescents together? I do my finishing in the evening hours, so natural light is not a possibility. What do the professional spray booths come with in terms of lighting? Do they make special glasses that help you see the clears? Any help is greatly appreciated.

Forum Responses
(Finishing Forum)
From contributor F:
I think you're on the right track with your panel mounted fluorescents. They are standard for pretty much all spray booth lighting installations. However, not all fluorescents are equal, and this is probably where your problem stems from. You need to achieve two things - the correct light intensity and a good light quality.

The first is easily enough achieved - you need about 100 foot-candles at a height of three feet from the floor. You can easily measure this with a light intensity meter.

The second is trickier. All lights have a rating called their color rendering index or CRI. This is a number between 1 and 100 where 1 is not good and 100 is perfect. A bog-standard fluorescent has a CRI of 62. This is nowhere good enough for spraying clear poly.

You will need to get lights with a CRI of at least 90. Watch out though because as a rule the higher the CRI, the lower the lumen output. The other part of light quality is the light color, or temperature, and this is measured in Kelvin (K).

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From contributor M:
To the original questioner: If I read what you said correctly, your lights are mounted above the work surface? I would suggest that you mount the lights on the wall. The light source needs to be at a low angle to the surface to be sprayed.

Think of it this way - when you are looking for imperfections in a finish, you hold the piece so that the light skips across it, not so it’s perpendicular to it. In the same way, when lights are mounted to the side of the work piece, it creates the same effect. I use sealed construction lights as I spray. I get the angle right, and I can easily see what is going on.