Step 1: Making It
WARNING - do NOT use an incandescent bulb! It will melt the plastic and start a fire!
What you need:
A two or three Iitre plastic milk bottle.
A compact flourescent bulb of up to 20 watts
A standard bayonet fitting for a beside lamp, or a pendant lamp (preferably with a switch).
A flex with a 3 amp plug.
Remove the cap and label from the bottle and cut off the bottom just below where the Iabel was.
Hold the securing collar inside the neck of the bottle and screw in the bottom half of the fitting from the outside, The type of collar shown is easiest to fit. A simple ring will work, but is more fiddly. A straight tapered collar may not screw in far enough for the bulb to fit, in which case you would need to shorten the neck of the bottle and perhaps use a washer on the outside.
Thread the rest of the fitting onto the fiex, connect the terminais and screw the fitting together.
Fit the bulb and the plug. Plug in and switch on!
Step 2: Using It
Set it on the open bottom as shown in the first picture. The weight of the bulb keeps it stable against the pull of the flex. If leaving it lit unattended for long periods you may wish to add some ventilation at the top.
As a directed light:
Hold, hang or clamp by the bottle handle. Hang the flex over the support to make it easier to adjust the angle. The shape is not a very efficient reflector, but can be slightly improved by lining it with foil.