In a shop light type fixture, the bulbs are usually space a few inches apart. This type of reflector creates light "stripes" when used close to the plants. The hood on a shop light helps to widen the light by reflecting the light coming from the top of the bulb. When you use this style reflector the light never leaves the top the bulb, instead its reflected back through the bulbs and sent out the front. If you doubt this works check with any aquarium shop and ask them.
The foil reflector: when you want the bulbs close to one another.
OK, all you need is a bulb and some 2 wide foil tape. Now, cut the tape so it is a couple of inches shorter than the bulb. This is for two reasons. First, the bulbs get hottest on the ends (heat can make the glue release and the ends of the tape will pull up). Second, it keeps the conductive foil away from the power at the end.
Before you start sticking the tape on, make SURE you have the bulb laying where the pins are horizontal to the floor. If your pins lock at an angle in the fixture, make appropriate compensations.
* Make sure you get the tape oriented with the correct florescent pin position when installed!*
Now start the tape about an inch from an end, and let the center on the tape stick to the very top the bulb. Keeping the tape straight, slowly run it down to the end. Tear off any excess at the end before sticking it past the last inch. Be sure to keep tension on the tape as you lay it - it helps to keeps the tape straight and centered (stops wrinkles).
Now that the center of the tape is stuck, start at the middle of the bulb and slowly make the tape touch a little more from the center out so that the tape is starting to take shape of the bulb. Work from the middle to end of the bulb. Dont try to get all the tape to stick in one try. The tape will not lift once set in place.
Note: trying to stretch a full length of foil tape and trying to lay it all-at-once onto the bulb is extremely difficult; if the tape touches anything it'll stick hard, and it tends to curl when you peel off the backing.
I took a comparison picture. The taped bulb is brighter and the light is focused downward. You still have some side lighting but as you can tell it is much less. The last picture is of a bulb that is over 30 days old and it shows no sign of phosphorous burning, stress or damage.
Using this technique you can literally create a wall of light. Floro's are not known for their power, so be sure to get all the light you can get out of them.
Editors Note: If your foil tape doesn't have clear adhesive, mylar can be used in it's place.
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