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Re: Ovens.

On 3/26 Al Hooten wrote, pertaining to oven bombarding:
        I would really appreciate any comments from the experienced
folks on the pluses and minuses of this kind of a decision.

        ALSO: has anybody on the list built their own oven? 
My comment:
You probably missed my comments on this one when I introduced myself. I have
not bombarded with an oven in my shop, because I have found that direct
heating with a hydrogen bushy annealing torch, painting the tubes, is much
faster and more flexible for a small custom neon shop. I, too, do not use
electrical bombarding, mainly because it is inefficient and unsafe. This
method has never been described in SOT, but it really avoids all the
complexities that Wayne Strattman identified in his article there talking
about it. All you do is heat the glass just up to the point where the orange
sodium flame just starts to come up, and go over it until the vacuum drops
again, while induction heating the electrodes. You continuously pump on the
tube, so you get out more of the impurities, and you can monitor the progress
of the bombarding process by watching your vacuum gauge go up initially, then
down to base pressure again as the outgass products get depleted. 
You probably would want to get a 240V circuit anyway if you use an oven,
since that is the most efficient manner to construct one. However, if you use
an open bench and just paint the flame on the tube, you never need to worry
about having a special configuation on the oven. I just use a flex metal hose
with an ultra-torr fitting to tube into, and my RF coils sit up anywhere on
the bench with the flex leads clamped to the edge of the bench to keep them
in place for whatever tube I am doing at the moment, in any flexible
configuration. Ovens force you to keep a very restrictive tube configuration.
Fine if you are doing a lot of similar production but not for a onesy-twosey
custom neon operation.
Jeff
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