heres something interesting i found back when i started. They work out pretty good imo.
HOW DO I MAKE A SIMPLE REFLECTOR FOR YOUR COMPACT FLUORESCENT?
To build this reflector you will need a regular soda can, any brand will do, which you will need to rinse thoroughly until no residue is left inside. You will also need a good pair or scissor and a robust kitchen knife to cut the metal accordingly. An alternate method to remove the lid, would be to use a can opener. The lip of the lid can be used, and it will cut it cleanly. These tools should be chosen carefully as they will determine over failure or success of this construction. A lack of caution and a sharp metal edge can be fatal to your fingertips so think twice if your tools are capable of doing the job.
How and where to cut:
Firstly, draw a plan of your cutting path on the outside of the can using a permanent marker or a wax crayon. This will aid you to get a better overview of you plan and to avoid silly mistakes on the way.
Cutting the top part of the can out needs to be done first, adjusting the opening according to the size of your bulb. You do not have to cut it exactly to shape as glue (super or high-temp hot glue) can be used to stick the reflector to the bulb ballast later on. A can opener is the preffered tool for this job. The reflector is purposely not covering the ballast to ensure good aeration and to avoid damage to the ballast components, resulting in a short circuit.
Next, you will need to cut the main part of your soda can in half using your scissors. A hole may need to be drilled first using your kitchen knife to get a good starting point for the scissors.
The inside of the can is coated with a thin plastic layer that should not cause any trouble cutting through the sheet metal. The bottom side of the can does not have to remain in place but leaving it will add stability to the reflector and enhance the reflectivity. An extra hole can be cut into the bottom as well to improve ventilation along the bulb or to connect a 50mm pc-fan to the end.
Lastly, two more cuts have to be made into the sides of the semi-circle reflector to ensure that the sides do not reflect the light back to its origin but rather focus it to where it is needed. The reflector can now be bent according to your light requirements thus making it possible to focus it directly on your plants. If your reflector does not quite fit the bulb yet you can now use glue to stick it to the ballast.
