Hi All!

 I've never pumped color glass before and have a few pieces that I'm working on... mainly Cobalt and Emerald uncoated... but I'd love to know if I need to pump these in a different way. Also any tips and tricks to do it right. 

Thanks!!

Hi Christine!  Well here's where I tell you the old glass was way better than the new glass...  Non-coated Bromo (cobalt) and Emerald are just tricky!  The following has been the scenario of late...   It seems as though the new non-coated Classic colors tend to off-gass impurities and can require multiple pumps (changing electrodes after they've been pumped once).  Pumping these units require high heat and excellant vacuum!  I have had so many units that seem to pump perfectly and start acting weird on the burn-in table.  I can go into this deeeper. I am kind of looking for someone else to chime-in and tag-team a bit...

Thanks for your thoughts, Al! Wow i hadn't heard about the new glass could require multiple pumps yikes... I was working with old stock but I'll have to keep this in mind. 

Hey Christine. Are you filling them with argon/hg or neon? An argon/hg fill won't require you to do much more than you would typically do while processing, but if you are filling them with neon you might run into trouble with them running hot or going dim in the middle. As Al mentioned, the uncoated colored tubing tends to have, and outgas, more impurities. You can do a "pre-process" by bombarding them with a neon fill, or even natural gas (which I have done before, under the advisement of David Ablon) which allows you to get the tubes very hot during bombarding. Do you have the book Neon Engineer's Handbook, by Morgan and Jacob? There is a chapter in it that talks about pumping uncoated ruby red, which you may find helpful. Lastly, I'd suggest making your units on the shorter size, as this seems to help. Say, 6' or less.

Hey Eve! I was pumping the cobalt with argon mercury but plan to use neon in the future as well so this is all great information from you. I had no idea it can get trickier with neon! I'll have to learn about the pre-processing and i do have the handbook so I'll read through that chapter for Ruby! :) Thanks!

As Eve alluded to, a neon backfill for processing can help....I've used this with uncoated ruby and it seems to work well......part of why it works is due to the molecular size of neon....it is similar to that of carbon, which is one of the impurities that tends to hide in the pores of the glass and so it can kind work its way in and push that out...or at least that is how it kinda seems to behave.  On a related note--Propane or Natural gas, as has historically been used for cleaning up mercury stains on repair units works because it is a hydrocarbon that wants to grab oxygen and will strip it away from the mercuric oxide stains and leave the metallic mercury behind, thus eliminating the stain.  It would also be useful as a backfill on new units where oxides are a contaminant of concern as it would have a similar effect on the glass wall as it does with the mercuric oxide stains in the coatings.