Navck said:
Got those here...
Hit on... Dim.
Wait about a minute, suddenly they'll get brighter, to about 60% brightness, then go 100% instantly (They start at 10% brightness). Annoying as hell in the hallway upstairs.
Well, actually those "dim starting CFL's" are much better than the instant bright ones.
CFL's operate by ionizing a mercury/argon gas fill. The pressure of the gas fill is directly related to the light output of the bulb: when the pressure is too low or too high, the lamp's output goes down very rapidly.
The cheaper CFL's have a drop of liquid mercury inside the glass tube: when the lamp warms up (due to the ionized argon gas), the mercury evaporates and the light output rises. But when you use the lamp at higher than normal temperatures (upside down, enclosed fixture etc), the output goes down (and not just a few percent...). The downside of an amalgam is that it takes a while to evaporate the solid mercury....a quite slowly rising light output is the result.
Better CFL's have a separate solid mercury reservoir attached to the tube called an amalgam. Most of the time you can hear a rattling sound when the lamp is shaken. This amalgam releases more mercury when the lamp is cold and absorbs mercury when it's too hot, hereby regulating the pressure and keeping the brightness constant.
Another important thing is the way how a CFL or fluorescent lamp is started. The instant on ones apply a very high voltage across the tube to ignite (ionize) the gas. This is very destructive for the electrodes. Each time the lamp is started, a part of the electrodes emissive coating evaporates...this leads to tube blackening and failure of the lamp (no emissive material = no light).
A better way to start a CFL is to preheat the electrodes for a small amount of time (1-2s) before ignition. This way, a lower ignition voltage is required to start the lamps and much less damage is done (to the electrodes, that is).
So, the CFL's with a delayed start are better than the instant on ones.