Contrabasso - 22-9-2010 at 22:11
I'm looking for a small amount of glass capillary tube and ebay currently offers none.
Has anyone a sharable supplier in the UK please or anyone a few bits spare within postal range of the UK
Even glass pasteur pipettes will do, but all seem to be plastic now.
MagicJigPipe - 22-9-2010 at 22:56
What do you need them for? I have a hundred or so of those glass tubes used for holding samples in a melting point apparatus. Are those small
enough? (they are closed at one end)
Contrabasso - 23-9-2010 at 13:00
I'm looking for the glass tip to an oxygen bubbler to clear RFNA. So I was thinking of something more like a broken thermometer a 5mm rod with a
capillary bore. Then I can simply get an oxygen cylinder and sparge (medical) oxygen into the RFNA and get WFNA. (BTW the cylinders come to me with
integral regulators which makes life so easy).
I don't make much but the distillation process seems to work well now, SG determination is by simply weighing a 20mi volumetric flask full - which
brings the mass into a good range on a small scale for three figure determinations.
peach - 23-9-2010 at 15:03
Funnily enough, I happen to have a broken thermometer I was hanging onto just in case the capillary might be useful. And I'm in the UK. PM me your
address and I'll stick it in the post when I hear back.
I also have an idea I'd like to try with an aspirator, do you still want that plastic one? 
If I don't break it in the process of trying the idea, I can always post it back.
{edit}Oh, it's a 300mm long mercury one, minus the mercury. It's snapped around the middle, so the pieces are about 4-6" I'd guess. It finally
developed a crack in the bulb, the column split (couldn't freeze / vibrate rejoin it) and it became unusable for any kind of accurate work, so I
harvested the shiny interior. And you don't have to loan me the aspirator, you can have a stick of the thermometer for free.
[Edited on 23-9-2010 by peach]
zed - 23-9-2010 at 16:59
"Pulling" a capillary tube from a piece of soft glass tubing, in the usual way, won't do?
Contrabasso - 25-9-2010 at 01:53
Sadly my only glass tube was described as "Pyrex" so it's not easy to work.
zed - 25-9-2010 at 18:49
Locally, the boys use oxy-propane for working Pyrex. I suppose that produces a lot more heat that the usual Bunsen Burner/Propane torch.
peach - 25-9-2010 at 19:02
Indeed it does, it's about 800C hotter.
Acetylene is a dream for heat, but not for glass I'm learning. There's another gas called MAPP, which is sooty like acetylene. Because it essentially
is.
According to my quick scooting around in between doing things. oxy hydrogen actually burns a little cooler than oxy propane, but with the benefit of
there being zero carbon around.
Natural gas burns similar to propane apparently. Which would be easier than buying cylinders if you're up to tapping into the gas mains.
I just dug my oxy/acetylene torch out, which I bought with all my christmas / birthday presents combined over a few years when I was in my early
teens. I'm looking at the cutting head and then the glass, then back to the torch.
[Edited on 26-9-2010 by peach]
MagicJigPipe - 25-9-2010 at 19:08
Regular propane works perfectly fine for working with borosilicate, in fact, adding oxygen is too much in my experience (unless you just use a little
bit of O2).
At the most I would use MAPP gas with no O2.
peach - 25-9-2010 at 19:09
For pulling? Or more complex stuff?
I've seen people with literally tens of dewars and monster cylinders full of fuel and oxygen at the glassblowing competitions. Is that purely for
speed?
I mean, theoretically I can silver solder with my propane torch. In practice, it's a major pain in the ass. I also tried switching to one of the
cheaper gases from acetylene and found, even though it would still cut, it took so much more patience to get it started and then keep it going on big
items (which obviously doesn't bother a CNC table, but it's a very tangible difference to me). Acetylene is like the plasma cutter of the gas cutting
/ welding world when compared against the others, to me.
{edit}Oh, I just remembered. If you google for MIT's digital lab manuals and then play the chromatography ones, they show you have to pull melting
point tubes and the idea behind pulling pipettes in the Bunsen.
[Edited on 26-9-2010 by peach]
zed - 26-9-2010 at 03:06
I once had a jeweler buddy that utilized Methane/Compressed-Air..... to power his muffle furnace.
Melted a pound or two of Silver at a time, and used it for lost-wax casting.
The natural gas burned hot, clean, and cheap. Though I suppose with O2, it might have burned hotter.
It also might require pressurization, for methane to produce the same oooomph as propane. A liter of methane at STP, contains only about 1/3 of the
potential energy of a liter of propane at STP.
As for Silver-Soldering....Am I recalling correctly, that once upon a time, jewelers used to Silver-Solder by means of a spirit-lamp and a blow-pipe?
-------------------------------------------------------------------------------
Well, I checked. They did.
I even found a cute little device, some of the guys here might find interesting.
http://www.autodidactics.com/blowpipesoldering/index.html
[Edited on 26-9-2010 by zed]
[Edited on 26-9-2010 by zed]
[Edited on 26-9-2010 by zed]
peach - 26-9-2010 at 08:55
Yep, I think the mains gas pressure may struggle a little in terms of pressure. At least the domestic lines in the UK. But boilers manage to get
enough blue flame heat out them, 20kW+.
It's not so much the gas, as the size of the flame that's required with it.
With jewelery, the bits being soldered are tiny. The heat loss is low and the mass that needs heating is low. But even silver soldering bits for all
those fridge pumps, like the 1" sized gaskets (about 1/8th thick and circle shapes), I have to absolutely roast them with the normal propane torch,
suspend then on bits of wire to stop them conducting heat and put blankets of foil around them to stop the heat convecting away. And then they only
just get hot enough. Usually needing five minutes or so to get there.
Same with big bits of iron / steel and propane. It works, it's just too easy for it to stop working.
Acetylene, I can pretty much be sure, it's going to get hot, quickly.
It's like trying to solder any semi-decent sized terminal with a 10 /15W soldering iron. Theoretically, it's hot enough. But the droop in the
temperature when it actually has a load attached, the heat sinking of the components, means I can end up sat there for three minutes waiting for the
part to get hot enough. If it ever does. Whilst the heat is conducting through the entire part, overheating it. Which is why I always go for the 30W+,
unregulated, budget irons and work quickly / carefully.
An air ionizer for the house is another example. It can manage thousands of volts. But, connect any kind of load across the pins and it's reduced to
nothing.
I wonder if you could work glass with a plasma flame? Tesla coil guys love them. Microwave oven discharges directed with some quartz tube?
[Edited on 26-9-2010 by peach]