Using UV to age or darken wood

Several custom cabinet makers have used SunMaster ultraviolet curing lamps over the last few years for the purpose of aging wood, to make it match existing wood in everything from kitchen cabinets to yachts. It has also been used by violin makers to darken the wood naturally, giving their instruments a warmer appearance. The lamps we recommend are RUVA reflector type lamps with higher than average UVA, to penetrate deeply and add warmth and depth to the color of wood, as well as matching the natural warmth that exposure gives wood over time.

Aging wood with UV cure lamps
1x3 pine strip, coated with Solarez curing resin, cured for 3 minutes, then aged under the same lamps for about 20 hours (right) and 43 hours (right). Center section was masked after initial curing to prevent aging and allow comparison. Using SunMaster Curall FR32T8 lamps powered at 50 watts.

Aging wood this way is very much an art, and it is impossible for us to give approximate times as it depends on the wood, the amount of aging the existing wood has, etc. Also, some people use this technique not to match existing wood, but for aging entirely new items simply for the effect it gives to the wood. This is common to bring out the grain or just give a warmer texture to the look of items. In general, people tend to expose the wood for as little as a few hours, or as much as a few days, but as the craftsman, it will take some trial and error, plus your own eye to determine the right exposure times for the effect you want to create.

UV will darken just about any woodSome items are trickier than others to expose evenly.The key with using UV to age wood is to do so evenly. This can be very tricky, as not all items are as flat as a board. This may require careful placement of the lamps and the stock within the UV cure chamber. As the amount of darkening will vary according to both how long you expose it and how far away the item is from the lamp itself, some experimenting is due before trying this on unusual shaped items. Keep in mind, the amount of UV that reaches the item drops exponentially as you increase the distance, so the difference between 2 inches and 4 inches isn't twice the UV, it is four times.

Of course, this can be used to create an interesting effect as well, by intentionally placing the lamp in a way so that part of the object gets significantly more UV than the rest of the object, creating a natural UV darkening gradient.

The lamps we recommend for this type of application include:

ClearTech 120R - $18.99 each, 1600 hours at 70% of rated output. Our best lamp for this purpose. Much higher UVA than any regular or reflector tanning lamp on the market. Uses a special glass that is more transparent to ultraviolet, so you get much more UV per watt. Super long life makes them more cost effective for the price.

SunMaster Pro Reflector - $14.99 each, 12 hours at 70% of rated output. Low UVB, closer to what the sun puts out but much stronger intensity over the entire spectrum.

SunMaster Reflex Bronzer - $15.99 each, same class as the Pro Reflector, but with about twice the UVB (5% of total UV output versus 2.5%). 1200 hours at 70% of rated output.

Note that these lamps have a peak output around 365nm-385nm, which is at the lower end of the UVA spectrum, where most UV curing resins prefer. You should always check with the manufacturer of your UV cure resin to make sure they are centered for UVA curing rather than UVB. These lamps have been tested with Solarez curing resins and found to be highly effective.

To power these lamps, you will need one Sunhorse ballast for every 4 lamps, plus two of our lamp holders for each lamp. You can also just look at one of our kits, which also includes the lamp holders. If you are wanting a different type of effect, say very high UVB instead, just call us and we will put together a special kit custom made for you. 1-800-274-1744 x126

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