Article 1-1 Evolution of Reflectors
You've just spent a small fortune on lighting equipment: metal halide and sodium in lamps; transformers, capacitors and starters; sockets, wiring and timers to make it all run. Your wallet is empty, your pets are at the pawn shop, and the reason behind this is very simple: you want to give your garden the best light possible, so your plants will grow well and produce great crop yield.
How you use your lighting equipment will determine how well it serves its purpose. For example, placing lights too close to the garden cooks your plants and hurts, not helps, your crop. A main point to consider is the efficiency of your lighting - how much of your lamp's output actually reaches the crop. Here's where the "tall crop" growers have it easy - they simply hang the bare lamps down among the plants and "broadside" their garden with direct light . But growers with "short crops" (plants under one meter tall ) use top-lighting, and that involves choosing a reflector from a wide selection of hoods.
Choose carefully - some reflectors are ten times as efficient as others. How did this happen? Why would anyone make reflectors that waste so much light? And which reflectors are most efficient? The answers to these questions demonstrate the rapid improvements in technology occurring in almost every area of hydroponic equipment today - improvements sparked by the explosive growth of the hydroponics marketplace. Manufacturers are improving products because there are more customers waiting for new, better equipment.
One of the problems with reflector design in the past was based on a misunderstanding of how H.I.D (High Intensity Discharge) lamps give off light. Unlike a typical incandescent "light bulb", HID lamps give their strongest light from the sides of the lamps. So vertical-mount reflectors turned out to be very inefficient - as little as 9% of the light was reaching the garden below. Ninety percent of the lamp's output ended up lighting the walls! While crops grew slowly with poor yields, the gardener was wasting a fortune to have the brightest walls in town!
Enter horizontal reflectors, which increased lighting efficiency. Turning the lamp sideways over the crop increased direct light levels to the crop, and the horizontal reflectors bounced more light down to the crop, too. Everything was wonderful - until lamps started to burn out after only a few months use!
And no wonder - the early horizontal hoods looked like recycled bread boxes! They trapped the heat around the lamps, making them burn out quickly. They also created the real possibility of electrical shorts in the socket wiring. Back to the drawing board! Next came horizontal reflectors with more open designs, with vents, even with small exhaust fans to remove and duct away hot air from the lamp and garden. With the basic design features for horizontal reflectors in place, manufacturers began searching for the most reflective material to use in their hoods. They needed a surface that would not only reflect the most light, but distribute it evenly onto the crop - no "hot spots", no shadowing. After years of research and testing, a flat white surface - coated with Titanium Oxide - gave the highest light levels, with the most even light distribution. It reflected 20 % more light than the best glossy white finish, without the uneven glare that's characteristic of high gloss surfaces. In fact, a unique method of applying the Titanium coating worked so well, it directed up to 95% of the light hitting the reflector down to the crop. Add this reflected light to the direct light from the bottom side of the lamp, and lighting efficiency in the garden became nearly perfect!
Gardeners quickly learned that these high-efficiency reflectors had a double benefit: Not only were their crops getting all the light from their H.I.D. lamps, but growers were able to move their growing systems to more open, accessible locations than in the past. How has an efficient reflector given growers this flexibility? Recall that old-style reflectors let most of the light escape to create very bright walls. Growers tried to re-direct some of this wasted light back to their crops, by covering the walls with Mylar or other reflective materials. But gardens had to be shoved into corners to take advantage of the reflective wall coverings. This created problems with poor air movement, heat build up and inaccessible plants.
Now consider the possibilities when using high-efficiency reflectors: all the light is directed onto the garden, with no wasted light on the walls. No need for reflective walls, and no need to cram plants into a corner of a room.
With gardens in a more open, accessible location, growers discovered that air movement was greatly improved, and heat build-ups disappeared, creating more even, consistent growing condition sin the garden. A free-standing garden with access from all sides of the grow room, allows growers to examine, prune or move all their plants, avoiding nasty surprises from bugs or diseases.
From 9% efficiency to nearly 100%! Reflectors have come a long way since the olden days, and we can enjoy the benefits now. This same story - of progress and improvement - could be told for much of the equipment and the supplies we work with in the garden.
The refinement of fertilizers, the improvement in HID lamps, the new growing systems - they make the early tools of the indoor gardener seem primitive and clumsy. So here's to all the dedicated souls who weren't satisfied with making crummy products - and had the determination to refine and improve them.