Re: NEON- 20 ft of 13 clear?

To: neon-l@lists.io.com
Subject: Re: NEON- 20 ft of 13 clear?
From: Morgan Crook <neonmc@earthlink.net>
Date: Wed, 20 Nov 1996 05:23:11 -0800 (PST)
Reply-To: neon-l@lists.io.com
Sender: owner-neon-l@io.com


>Any suggestions that I could use for the next time?  Have any of you had
>this happen to you?  We are talking 20ft.  Why would someone design a
>channel letter with one unit like this?  I was actually thinking for a
>minute to break the tube and make two units out of it.
>
>Thanks for any replies in advance.
>
>Howie Cohen
>Just Neon


Howie, the other post have been very good on the subject; let me add a
couple of things.
 
Preheating the tube REALLY helps by removing most of the crap that was
making the pressure jump around so much; giving you much more control over
the pumping process. (Heat tube to 125 C or so,at pretty much whatever
pressure, let cool under vacuum til you can hold the tube, and backfill with
2 mm air (don't let the tube to atmosphere) and bombard as usuall).
Actually, we preheat just about everything greater than 6-7 feet just to
maintain tighter pumping viriables.

On the worst of tubes in some other shops I have worked in,  I have attached
tubes and let them pull doun for 10 min. before we ever do a preheat which
can pull of some of the trash in the tube (this is rare, but can help if you
have really underpowered equipment.  If you need to do this to make this
process work you should really think about spending some money on hardware).

But the bottom line is, pumping tubes this big you are not following the
processing instructions for the electrodes.  You are going to end up with
problems.

Morgan