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

In article ,
writes:
Hi - what lightbulbs are best for taking the ends off and making an
hour-glass?

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

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

Also, what is the best way to take the ends
off?

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
[email address is not usable -- followup in the newsgroup]

Andrew Gabriel wrote:

(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.)

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

On May 16, 11:05*pm, wrote:
Hi - what lightbulbs are best for taking the ends off and making an
hour-glass?

Big ones!

I'd probably try some of the Halogen-A bulbs, where there's a big
glass envelope as a safety cover around a small halogen capsule. These
are quite strong.

Criteria are that it's not dangerous to take the ends off,
so presumably they shouldn't be gas-filled,

Not a problem.

Also, what is the best way to take the ends off?

Practice. You don't need many, so just be careful and expect some
wastage. I do this to make oil lamps. You need to remove the ends
(just hit them lightly on the side with a steel ruler), then cut the
bowls neatly, and to do these as two separate operations. Even though
I have a glass-cutting bandsaw, I can't see a way to do both in one
operation. Probably wise to scribe the edge of the cut with a diamond
before breaking, just as a crack stop.

To make smooth cuts, the old party tricks are still good and work
quite well on thin bulbs. Wedge the bulb facing upwards in a pot of
sand. Fill it with engine oil to the level of the cut. Heat the poker
up in the coal fire until it's red hot, then dip it in the oil.
Thermal shock takes the bulbs off quite cleanly.

Watch out for smoke & even oil fires! I do this stuff (and many
similar things) in an old ammo box filled with sand. If it catches
fire (about ten times a day), I kick the lid shut and just let it go
out of its own accord.


All of this is dead easy. However the hard part is making the
measuring hole, which needs to be smooth and the right size for the
sand grains you're using. This is made by drawing down some glass tube
in a torch flame, then usually by blowing bulbs on either side. I
really can't think how to make this without lamp-working of glass
tube.