Yeah, it seems silly. But remember that CFLs don't give off heat. So if you want to conceal part of the bulb, go for the spray can like this Ikea hacker.
With a desire to replace his old, high-wattage bulbs, Ikea hacker Stefan ventured to the Sweedish flat-pack retailer for some cheap Sparsam CFL bulbs.
But there was a problem. His industrial-cool light fixture shows the whole bulb, so the visible labels on the Sparsam were a little unsightly.
His solution? Silver spray paint. With a little painter's tape, you can mark the part of the bulb to be covered and voila—ugly labels gone!. You could also use this technique to block off light from part of bulb, like if you wanted a corner-hanging pendant light to shine only into the room and not on the walls.