Message-ID: <3B195832.299A3443@bellsouth.net>
From: John De Armond
Newsgroups: rec.crafts.glass
Subject: Re: Glass radio tube cutting: how ?
Date: Sat, 02 Jun 2001 17:18:43 -0400

m28 wrote:
>
> I want to make an installation with old radio tubes.
> I need to remove the glass bulbs.
> I heard that you can cut glass tubes by knotting a rope around the tube, wet
> the rope with alcohol and light it in flames. That should break the tube
> right where the rope was sitting.

That generally doesn't work on tube envelopes because most are
borosilicate glass.  What does work is to score the cut line, heat
the line with a hot wire (nichrome (or even iron) wire heated with a
car battery or equiv) and then touching the heated line with a drop
of water.  If you're lucky, the crack will run all the way around
the tube.  If not, you have to quickly touch the heated place with
water at several places around the tube.  You can usually run the
crack by tapping at the leading edge with the end of a glass cutter
or something else smooth and metal.  In most cases, I find that
simply licking my finger and touching it to the glass is sufficient
moisture.