The Turn Of The Century
Age Identification of Crookes, Geissler & X Ray Tube
This is a guide for estimating the
approximate age of X ray, Crookes and Geissler tubes.
First was platinum, then Dumet wire
(copper colored) came into use around 1912. This is the current feedthru
wire still used today.
What you cannot see is they still had
platinum feedthru in the glass seal and then the copper was welded to the
platinum. They did this up till the Dumet wire so they could save cost on
Any tube with Dumet wire is later than 1912 to the present.
The first connections were a platinum
loop where the end of the loop was fused back into the glass, then the
conical or domed shaped cap, either brass or nickel plated, then the
cylindrical and on the latest Pressler repros, grid caps off radio tubes.
The cylindrical caps came on a scene in the 20's and continue thru today. The earlier ones were nicer and better formed, the later ones were crude and bigger.
The first were solid small pieces of
aluminum rod with a hole in one end and the feedthru wire put in the
hole and crimped. This is still typical of today. The big difference was
because of the platinum wire, the electrode had no support so the
electrode was "glued" to the glass feedthru post by lead foil and gum
cement wrapped around the end of the electrode and the stem.
The early tubes were truly works of art,
coils were uniform and still round, any bends were round, not flattened.
Any splices of glass had invisible seams and looked like a single piece of
glass of uniform thickness.
In Geissler tubes from the turn of the century in 1900 you may find a ruby glass electrode stem present. This was used in an attempt to make a better seal with the electrode feedthru wire. Although it made the internal of the tube very interesting, it was not any more successful and dropped in later tubes due to construction complications.
Many modern high power radio tubes used
uranium oxide glass transition seals for their electrode wires.
Modern Geissler tubes may have Neon or Mercury in them to make the tube brighter but it was not found in the original tubes.
Crookes and Geissler used only rarified
Frank Jones Jan 2006