oad strokes | Tech Savvy 14 <strong>Professional</strong> <strong>Painter</strong> • Winter 2011
Colour Matching 101 E very paint has a unique set of characteristics and ingredients—sheen level, elasticity, opaqueness, tint quality, base quality, the nature of the fillers and VOC levels. If the paint is more than five years old, it is possible that even the formulation has changed; Witness the drastic changes in the last two years due to changing VOC regulations. There are a host of variables that need to be taken into account. Add to that the fact that, as we all know, not all paint is created equally, and where some are hard to match no matter what you do, others seem made for matching. Matching over time Even if you find a paint that matches the sheen level of the existing wall, new and old paint have different sheens and will fade differently. Older high-VOC paints break down much faster, and so even if the sheen matches after you touch it up with a mini-roller, a few months later the spots stand out. If you think the wall is situated where variable sheen will show, matching may not be the best way to go. Computer matching The most common way to match paint colours today is with the use of a computer matching system. With an accuracy of about 90 per cent, computer-based matching is nearly perfect for the untrained eye. For that next ten per cent, it takes the matching ability of the computer plus the experience of a good colour-matching technician who can adjust the computer-derived colour with small amounts of tint to get it just right. How the computer does it Computer matching uses a spectrophotometer that scans the paint sample using a tungsten bulb to simulate daylight. The bulb produces pure white light since white light is made up of all the colours of the visible light spectrum. Newer machines use light emitting diodes (LEDs) that are even more accurate and use less power. <strong>Professional</strong> <strong>Painter</strong> • Winter 2011 Constantly changing paint formulations have made accurate, invisible touchups almost, but not completely, impossible By Bruce MacKinnon The paint sample to be matched is held in front of the light box and flooded with white light that reflects off the sample onto a small wheel at the back of the light chamber. The rotating wheel is a highly-efficient analyzer, made up of as many as 31 interference filters. Each filter is designed to allow only a specific wavelength (ten nanometres worth) of light to pass through it, while all the other colours are reflected away. Fiber optic cables then transmit the colour information collected to a photo diode that digitizes the information for the computer software to read and create the perfect recipe of tints in a specific paint base to match the paint sample. Base and paint line effect The paint base and the paint line are critical. Only topline paints should be used when tinting because they hold colour longer. Also, flatter paint will return a more accurate tint-matching combination, as glossier paint makes the processing of the chip more unreliable. A glossy colour sample will cause glare and reflect light off the sample. The latest spectrophotometers come equipped with LED lights that create a laser-like beam of light that can reflect off an object and reject ambient light in the room. This means painted samples like rad covers or metal can be brought in to be read and don’t have to be clamped to the light box in front of the machine. When you are done matching Once a sample has been matched and a small amount of paint is mixed up, the new paint should be rolled on using a mini-roller to more accurately create the roller texture and stippled effect of the paint. The tighter the nap of the roller at the time of application the glossier the finish, so matching the paint texture on the wall is just as important. 15
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