what lightbulbs best for taking ends off and making hour-glass?

Hi - what lightbulbs are best for taking the ends off and making an hour-glass? Criteria are that it's not dangerous to take the ends off, so presumably they shouldn't be gas-filled, and that they are transparent and strong. Also, what is the best way to take the ends off?
Thanks for any help with this!
Michael
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     snipped-for-privacy@yahoo.co.uk writes:

By joining two bulbs at the neck? I think that would make a half-second glass, not an hour glass!

Ordinary filament bulbs. They are gas filled (above 25W), but the gas is inert (usually nitrogen or argon).

Very many years ago, I took the bulbs off 300W and 500W GLS lamps (and a few regular 100W ones). I filed a line around the neck using the corner edge of a small file. Then tried a few ways to make it break along the line, such as tapping it, and using a blob of solder hanging off the end of a soldering iron to generate some differential expansion. These both worked, but were not highly reliable and the neck fracture didn't always follow the line. Hot resistance wire is another method (I didn't try).
The bulbs are slightly toughened on the outer surface only which adds considerable handling strength to the very thin glass. (Apparently when dropped onto a hard floor before the guts and base are fitted, they will often bounce a bit like a ping-pong ball.) However, this does make them harder to break cleanly when you want to.
Something else you might try (I haven't, as I didn't have one back then) would be a small cutting disk on a dremel. Submerging most or all of the bulb under water might reduce the chance of it breaking in the process. (You can cut glass microscope slide cover slips with scissors under water, because the water absorbs the high frequences which cause it to shatter if you try doing this in air.)
--
Andrew Gabriel
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Andrew Gabriel wrote:

Doh! I remember trying this as a school lad, without success, and wondering how it might ever work. Of course it was slide *cover slips*, not the (much thicker) slides themselves, you were suppposed to try ;-o
J^n
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