Intro: Dirt Cheap DIY CFL Reflector
Compact Fluorescent Lamp (CFL) bulbs are designed to emit more light from the side than the top. This works great for table lamps, but not so well for photography or indoor horticulture. To get the light heading in the right direction we need a reflector. If you only need one or two, inexpensive shop lights are a probably better choice. I needed 10-12 for my photography/videography light project, so decided to build my own and save some serious cash! Like almost all of my projects, I made it at TechShop! http://www.techshop.ws
1) This project is for 23W or less CFL's only! Incandescent lights get much hotter and will pose a fire risk.
2) This project involves metal cutting and grinding. Take care and use all appropriate safety procedures!
3) CFL bulbs are fragile and contain mercury vapor. Always handle them carefully with gloves and screw them in by the base rather than the bulb. Remember to always dispose of them properly.
4) Create and use this at your own risk! My CFL's don't get hot, but yours might.
Learn what to do before you break a CFL bulb!
Step 1: Get Stuff!
Materials Per Reflector:
(1) Stainless or aluminum 'Dollar Store' bowl - $0.99
(2) 3 inch PVC Knock-out cap - $0.60
(1) 3 inch PVC pipe 2-1/4 in long - ~$0.50
(3) 3/8 inch screws #4 or #6 - ~ $0.20
(3) 1 inch #8 screws - ~$0.40
(1) 1 Inch Metal Conduit Hanger (Aka 'rigid clamp') ~$0.79
(1) Package of Metal Filled Epoxy
(1) Spray Truck Bed Coating ~ 6.00
Red Handled Tin Snips (Red for right handed people, green for left)
Drill Grinding Stone (Optional)
1 inch hole saw (Optional)
Step 2: Reflect for a Moment
Bowls come in various sizes and shapes. The ones with rounded sides give better results than the ones with sloped sides. I used 1.2 qt mixing bowls with a 7 inch diameter. This was about as small as I could find without special ordering them. My bowls were slightly more than 2-1/2 inches deep so when the reflector was finished the standard lamp bulb did not rise above the reflector rim. This provided a little more protection for the bulb from accidental bumps. For bigger bulbs, you need bigger reflectors. The bulbs I used were 23W (100 watt equivalent) CFL's). Higher output bulbs are larger, sometimes much larger.
I had great success finding inexpensive stainless steel bowls locally at restaurant supply stores and 'Dollar Stores'. Cheaper means thinner metal, for our purposes the thinner the metal the better. My bowls cost $ 0.99 at a local store by a very very similar name. ;) . I won't spend much more much $1.50 on a bowl unless it is for a 'Beauty Ring'. Spending a lot on the bowl at a big chain store makes this project less attractive. At a total cost around $3.00 per reflector it is an excellent deal.
Step 3: Find Your Center
I prefer to so this carefully with a compass, but alternatively you could just take a short piece of PVC pipe, eyeball it on the bowl, and trace around the inside. I have had mixed results using this method (my eyeballs may be crooked), so I use the compass to carefully mark my first opening and use it to mark the other reflectors.
Quick and easy compass method:
In higher quality bowls manufacturers often polish the bottoms to remove the manufacturing marks. In 'Dollar Store' bowls, this is most often not the case. Look at the bottom of the bowl in bright light. Often you will see rings from the manufacturing process.
Find the center and place a small dot with a pencil or fine Sharpie to make it easier to locate for the next step.
Step 4: Visualize Your Hole
Place several small pieces of clear tape over center dot to give the compass something to penetrate. Packing tape works best, but scotch can be used if that is all you have. Now draw a circle the diameter of your knockout cap. The inside diameter of the pipe is 3 inches, so I set the compass to a little over 1 1/2 and created my circle. If you have trouble seeing your line, you can place masking tape over the edge and draw your line on that.
Step 5: This Is Only a Drill
Stack all of the bowl reflectors together and drill a large starting hole 1/2 inch from line. Drilling starter holes all at once saves time. If you drill bit isn't large enough you can drill several holes next to each other.
The starting hole is moved away from the line to give you room to bend the metal a little. This sometimes happens because the tip of the snips is too large for the hole and can crease the reflector.
Placing the stack of bowls right side up on a piece of scrap wood and drilling seems to work best. Hold the bowls firmly to keep them from slipping and go slowly to avoid ruining your drill bit, stainless is hard metal.
Step 6: Snip Snip
Now we need to create a reflector to use as a pattern for the others. Cutting counterclockwise if you are right handed with red snips and clockwise with green handled snips if you are left handed, start cutting metal in a spiral shape until you reach your line. While cutting you should be on the line or slightly inside it. The closer you get to the line the less smoothing you have to do in the next step.
Step 7: It Won't Fit!
Using a drill grinding stone or a Dremel, smooth the opening until the knockout cap slides through with a little resistance. I used a drill press mounted grinding stone, but a hand drill or Dremel will also work. It isn’t absolutely required to use a drill press or Dremel, it can be done with the shears. It takes longer, but if you don’t have a power tool you don’t have to buy one.
Now you can use your first reflector to mark all your other reflector bowls. I made mine in a batch, which significantly cut production time. I even stacked them to smooth them all at once!
Step 8: How Long Should It Be?
For my reflectors I needed a piece of pipe 2-1/4 inches long. Your length will vary based on your light fixture and how you attach it (some examples on mounting are included later). Keep in mind you are trying to put the bulb below the rim of the reflector (see pictures). This will provide some protection from mishaps.
I cut the PVC with a power miter saw, but it can be done easily with a hacksaw if you are careful. You can make a flexible ruler from the factory cut edge of a file folder. Wrap it around the pipe as shown and draw the line.
Sand and smooth the edges of the pipe with fine sandpaper. If you plan on painting the reflector for a more professional look, lightly sand the outside of the pipe and the outside of the bowl until the finish is no longer shiny. This will help the paint stick. If you intend on painting the inside of your reflector white for a more diffused light, sand it also. I skipped it because the bulbs diffuser coating seemed to be diffusing the light well.
Step 9: Knock It Out
Slide the cap through the hole in the reflector. Then press it into the short length of PVC pipe. Use your utility knife to score the inside of the knockout cap. Place it on something solid and hit the center with the hammer until it breaks lose. Break off all the pieces and smooth the edges with your utility knife, file, or sandpaper.
Step 10: Taming of the Screws
To secure the reflector drill two or three holes slightly smaller than your screws, spacing them evenly around the top of the PVC pipe and cap.
Install screws. PVC is soft, so the screws should bite into the material and hold the reflector firmly. You could also use PVC cement to lock the pieces together permanently. If decide to go that route, glue everything together just prior to painting. I used screws to make it easier to replace the reflector if I needed to, and since I didn't have PVC cement the screws were cheaper.
Step 11: Socket Mounting
At this point the reflector just needs a knockout cap to connect to. How you mount the reflector depends on your choice of electrical sockets. Here is one idea that provides great flexibility and fits a wide variety of sockets.
Making the socket holder:
Take your second knockout cap and locate its center. Using a utility knife, remove the plastic bump.
Using a 1 inch hole saw in a drill, cut a hole. If you don't have access to a drill, scribe a hole 1-1/8 in diameter and cut it out with a utility knife.
Align your conduit hanger in the middle of the cap as shown. Caps vary, so you may need to trim the tab to get the hanger centered. side should rest against the tab.
Drill 2 holes at the points shown.
Cut or drill ventilation holes as shown.
Screw the 1 inch #8 screws in the holes.
Clean everything to remove any oil or debris before applying epoxy.
Following the instructions on the epoxy package, epoxy the screws to the metal conduit hanger. Allow 24 Hours for the epoxy to fully set.
The screws provide a mechanical connection between the clamp and cap. I have had mixed results with epoxy alone, it doesn't seem to stick to PVC well.
Step 12: A Smooth Finish
Painting is optional but highly recommended! I like to make my DIY projects look similar to professional products. I also find that if I take the time to make something look nice, I value it more, I treat it better, and it lasts longer.
Disassemble and clean the reflector thoroughly with alcohol or mild detergent and let it dry completely. Any moisture trapped in joints will ruin your paint! Paint the back with at least two thin coats of black "Truck bed coating" (Not 'Undercoating') and allow to dry (I usually give it a couple of days to fully harden). This gives you a durable non-slip textured surface similar to professional photographic equipment. Another option is primer and flat black paint. It is less durable but it gives you a smoother finish.
Optionally, paint the inside of the reflector flat white to create a more soft diffused light. I didn't need it for this project.
Step 13: Profit!
There you have it, a professional looking CFL reflector for around $3 each. They probably aren't optimized for maximum reflection, but you certainly can't beat the price!
Step 14: Blooper Reel: AKA Things I Tried and Rejected
I started off with 2” PVC pipe. The bulbs fit, but the pipe doesn't allow any air to circulate around the base. The base on some bulbs get hot, and I was worried about melting the plastic and shortening the life of the bulb. The smaller diameter of the 2 Inch PVC also made mounting the plug adapter version more difficult than it needed to be. I couldn't figure out how to secure well enough without spending a lot of time cutting slots.
2-1/2 inch PVC would be large enough and is available as electrical conduit, but they don't make knock-outs for conduit! :(
Using a hole saw to make the opening in the stainless bowls, even a famous name brand with a bi-metal blade, didn't work. I will have to revisit this at some point, I don't understand why.
One prototype used a 2 inch coupler. It was a little larger, but still gave very little room for air to move. Unfortunately it required an additional ring of pipe to lock the reflector. It didn't seem worth it to add the cost of a coupler and an extra cut for so little benefit.