On 05/05/18 16:40, Neon John wrote:
On Fri, 4 May 2018 23:06:32 +0100, David Billington
wrote:


All the bead makers I know use stainless steel mandrels without issue.
The area where the bead is built up is coated with some sort of ceramic
wash applied wet and allowed to dry before the bead is started. When the
bead has been formed and annealed and allowed to cool the bead and
mandrel is soaked in water to allow removal of the bead.
Yes, one can do it that way but then the glass is not in contact with
SS but with colloidal silica. The base metal can be anything. Extra
hassle coating the mandrel and getting the silica out of the bead's
bore afterward as compared to simply using graphite.

One issue with
graphite in contact with glass is that it can contaminate the glass
surface, not likely an issue on the inside of a bead, but an issue when
graphite is used against glass to shape it but a quick heat in a glory
hole can remove the contamination.
Maybe it can but I've never seen it happen.
It's a problem that was mentioned to me during a masterclass by a highly
skilled glass blower that does top quality work and it was particularly
mentioned in relation to colour bar picked up on the end of the iron and
worked with a graphite paddle. If the colour was shaped and gathered
over without a firing in the glory hole first the graphite could leave a
taint on the surface which was visible later.


John

John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address