Lighting for Accurate Colour Matching

Half the secret of good furniture colouring is in the choice of workshop lighting. Banks of fluorescent lamps may wash a room with an abundance of ambient light and represent an agreeable balance between light quality, lamp longevity and ultimately, cost, but won’t necessarily provide satisfactory colour temperature when it comes to colour matching and furniture finishing.

The colour quality of light consists of colour temperature and colour rendering. Colour temperature (expressed in Kelvins) determines the coolness or warmth of the light. Colour rendering (expressed numerically on the colour rendering index on a scale from 0 to 100, with the higher values being more desirable) is the ability of a light source to reveal the true relationship between colours. Poor colour rendering will blur similar colours.

The finishing area, or room, should be specifically lit for colour matching. Gone are the days of mixing various colour temperature fluorescent lamps with halogen lamps to achieve accurate colour matching conditions. Most lighting manufacturers now produce T8 tri-phosphor fluorescent lamps with a colour rendering index in the high nineties; typically Ra 98 with a colour temperature of 5300 K. These will provide precise colour matching conditions for finishing furniture.

Another important area to consider is the problem of reflections on shiny surfaces such as polished table tops. Reflections can obscure the wood’s figure and true colour. Small to medium external windows are a common source of reflections and, odd as it may sound, should be avoided unless the daylight is entering at ninety degrees to the work. Large windows and glass walls can however work to the advantage of the overall lighting.

Ideally, any direct light should come from the side as it lights the work and then reflects off to the other side. A light source in front of the work will reflect up into your eyes and should similarly be avoided.

One last consideration when it comes to fluorescent fittings: Flickering, humming lamps are an acute annoyance in a quiet workshop (to me at any rate), but they too are a thing of the past – or at least they can be.

All fluorescent lamps require ballasts to function and the constant, low frequency cycling of the older magnetic types caused the familiar flickering and humming. Modern electronic ballasts operate at thousands of cycles per second, eliminating any flickering. Be sure when you specify your lighting that your electrician installs electronic ballasts.

 

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About Jack Plane

Formerly from the UK, Jack is a retired antiques dealer and self-taught woodworker, now living in Australia.
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