Note, as they say on wikipedia, this is a "stub" that I plan to fill in with details as I warm up the scanner and go take some pix of doing all this in my lab.
One wants to read just about any of Kohl's books on the topic of glass or ceramic -- an utter gold mine of good how-to information. John Strong's book is a great reference on quartz and working it -- but that is way not for beginners unless you have some good amount of practice stock and some time to master it. I guess the good thing is that it makes pyrex seem easy after that.
I use 3 types of "glassy" things here. One is Pyrex 7740 (same as Kimble K-33), another is lead glass as used (and bought cheaply in bulk) for neon signs, and the last is quartz from quartz.com.
These pretty much span the range of properties you'd want in a normal lab. Quartz is a fantastic insulator, makes good fibers, a great light pipe but is hard to work without some special tooling. Pyrex is easy to work, a lousy insulator (by glass standards) but that's not always a problem -- you get an intrinsic voltage divider, sort of, using it, and it seals to tungsten quite well and fairly easily. Lead glass is a good insulator (nothing beats quartz, but this is better than pyrex), and has a high tempco that matches some other metals well -- I've sealed Ti wire through it with no problems. I lack a source of DuMet or Kovar to try with, but they should do fine as well -- this is what the bases of many vacuum tubes are made of, while a less insulating glass is used for the bulbs to keep electron charge from building up on the bulb and messing up tube operation.
I found some "didymum" [sic] glasses for working with pyrex (or any soda containing glass) that work like magic and only cut the sodium optical lines out of the view so you can really see what you're doing without the yellow flare blinding you. They are becoming harder to find these days, as they don't cut UV or IR so the newer types (that cost ten times more) are what you mostly find unless you know what you are looking for. I found mine on an art-glass supply webpage I lost the link to (I will look again, but if anyone finds it first, chime in!) for about $40. I made my own propane/oxygen micro torch for pyrex and lead glass,
and for some of the smaller quartz work, but for anything not tiny, you need oxy-acetylene for quartz and real welding goggles, not to mention a fair amount of serious practice as quartz vaporizes not far above the working temperature, and leaves this white coating of condensed quartz stuck all over the work if you push it at all -- it's a delicate temperature balance right around blinding white hot. You have to work quartz while it's still pretty viscous, you can't heat it "runny" and get away with it, so more prep is also needed, as well as jigging for any good work with it.
I cut quartz and some larger glass tubing with a tool post grinder I made for my lathe, with a diamond wheel on it. I run the lathe slow (about 60 rpm) and the wheel fast, and use water from an eyedropper for lube and get perfect cuts everytime. Further, you can also use other diamond bits to chamfer ends (so for example you can slide them over O rings easily) as well. I also use diamond hole saws (sometimes found cheap at harbor freight) to make holes even in the sides of tubing. For that case, you use some modelling clay to make a little dam around where the hole is going and fill that with water as a lube and coolant, and just go slow with constant pressure on the drill press -- and you get through pretty quick. For holing flat things, I wax or water-stick a sacrificial backing plate so the tool won't chip the work when it breaks through -- going slow and with low feed pressure is key for that.
For stress checking any work, we made a crossed polarizer light table to put the work in to see if there is a lot of stress in any joint. Most things other than quartz need to be annealed after working them (various techniques are possible) or they will suddenly explode without warning sometime later on. Kohl's new book (at least, didn't check the old one) has some time/temperature curves for best annealing, and I have a heat treat oven I use for critical pieces that can be programmed to do that. Many other glass blowers simply turn off the oxygen when done, but keep the sooty flame on the work till it gets coated thickly with soot, cooling it slowly enough -- most of the time, but this isn't always good enough or at least not for me, but then again, I'm not truly expert, just good enough to make what I want, which tends to be tempered with what I think I can pull off .
In a way glass working is like welding or some other things -- it's all the prep, the jigs, and the other tools. Too late to fish for something once you get it hot, you have to be ready, and performance visualization is a good technique to practice before starting the torch. Glass (or quartz) doesn't stick to graphite (even the low grade stuff like welder's gouging rods) so you need some of that -- with insulating handles, as graphite is pretty thermally conductive, which causes other issues if you hit hot glass with it cold, and quickly burnt fingers if you don't put it into a good handle. Various shapes of graphite tools and jigs are well worth making for this work. I made some nice inserts for the tubing sizes I have to help make creating "tees" much easier -- you put one in the tubing you've put a hole in (I use the hole saw) and that keeps it from collapsing while you weld on the sidearm -- you can now use a bit of force and/or take your time at that job (maybe using some cane to fill in the weld joint and make a "bead" there for strength. On the other hand, you sometimes want something that does stick to hot glass, and for that I use a tungsten welding rod in a holder to for example, pull off excess glass for which it works better than a piece of cane.
For what it's worth, here's how I make a tungsten/pyrex seal. I use TIG welding rods, either .040 or .0625 usually, but wire works just as well -- the rods are cheaper.
First you get it clean. I've never even tried the "dip in molten nitrite" thing, just sand them off a little with fine grit seems fine. You then pass them through the torch flame for a very short time. You just want to see a blue oxide on there -- if you go too long, it turns other colors or black -- start over. No matter what size I'm going to seal it into, I begin by drawing out a section of thin pyrex from a 1/4" piece of tubing to about the same size as the tungsten, a little larger for a loose fit. Slip this over the rod, being careful not to scratch that oxide -- or start over again. Then, working from one end, put it in the torch and slowly melt the glass to the tungsten (surface tension will do this for you) starting at one end and working to the other so you dirve out any air trapped in there. A few bubbles won't hurt this, but there shouldn't be many. Now the thing is safe to leave laying around. When needed, you just melt it into the end of some pyrex tubing, using whatever heat is required to make it shrink down that much and fit. That's the easy part. You should anneal this seal before use, preferably with the "soot" method, and perhaps in the oven later If it looks good under a magnifier when you make it, it's good, but may crack later if not well annealed and leak. Tungsten rod often has longitudinal channels in it. The only way to fix that is to seal the ends. I have heard of using braze to do this but haven't used that (not sure which alloy would wet the tungsten) -- the advantage would be you could solder a wire to the air end. I simply use my tig welder to melt the ends, then spot weld to the air side. To make that work, I wind the wire around a few times for mechanical strain relief, then just spot weld the end away from the rod end (eg close to the glass part).
I have used the same basic technique to put Ti wire (.032") into lead glass. Here there's enough tempco mismatch that I use Hysol epoxy or real glyptal after to keep the seal good, and the glass is mainly the mechanical strength part. Hysol from McMaster is pretty good vacuum epoxy if you really mix the snot out of it and use it carefully, and then don't get it too hot. It takes quite a long time to cure, so you have to be patient and not even touch it for 24 hours after putting it in a warm place to cure.
As I said above, this is a big one, and I will get back here soon and fill in a lot more info from the various books and actual experiences here. I think there's so much this might deserve a fairly long set of responses just to keep it organized.