Not all compact florescents are the same!

I've had some that are delayed in lighting after throwing the switch and other's that take tens of seconds to make it to full brightness. The good ones come on instantly and reach full brightness very quick. Trouble is, I don't know which brands are good and which are bad. I bought some tonight at Costco that are doable but they take a second or so to light up after throwing the switch.

I've read somewhere (here I think) that the CFLs that have to warm up to reach full brightness contain a specially tweaked gas mixture so they can be operated in base up or base down position without a loss of brightness when in the base-up position. I have several CFLs here that have to warm up to reach full brightness. It's kind of funny how they slowly get brighter, then after about 20-30 seconds they brighten rapidly to their full output.

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.

Yes, I know what you mean. The weird thing is most of the CFL's that start fast that I own were discontinued and purchased very inexpensively. The only currently available CFL's that start instantaneously that I know of are DuraBright brand. They have "FastStart Technology" labeled on their package. OSH currently has them on sale for 20% off. The only exception to this is their 3-way CFL, they are really slow at starting. I returned those CFL immediately.

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.

Click to expand...

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.

I just bought some Honeywell CFLs today. They are a huge improvement over the "Commercial Electric" brand that I had previously (purchased in bulk packs at Home Depot). They appear to come on bright right away. They're brighter, too.

The DuraBright 60-75-100W equlvalent ones are $1 each supposedly in cooperation with local utility.

I tried a few different ones. They all BUZZ like crazy. Bought a GE and problem solved for now.

The Magnetic Ballast Strikes again!

(If it hums, its a transformer type-- cheap and well cheap)

(No hum == electronic solid state switching inverter-- not so cheap and more efficient)

The GE brand of CFL with the bent tubes (Biax) takes much longer to light up than their equivalent wattage spiral lamps. The Biax are more expensive but are supposed to last longer, however, they usually don't. The Biax GE lamps often fail in a month or so and the odds of getting one that lasts long is poor.

Better not use these in small, unvented, fixtures or the PCB will self destruct. Not too good for cold areas when instant light is needed.

Melchior said:

(If it hums, its a transformer type-- cheap and well cheap)

Click to expand...

I thought it hummed because it didn't know the words. :shrug:

eluminator - I for one appreciate your sense of humor!

& I 4 2.