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Re: bottle stopper?

> Date: Fri, 4 Jul 1997 15:04:03 -0700
> From: olga at arts_ubc.ca
> Subject: bottle stopper?

> I'm having difficulty with the DIY CO2 that I run on my smaller tanks.
> problem is that the caps on the bottles don't hold their seal well over
> time. I have siliconed them well and when I first get a bottle set up it
> works fine. However, after time they seem to leak no matter what.
> I was thinking that it might be better to invest in some good quality
> rubber stoppers with holes in them for glass tubes (like in chemistry
> in high school -- gee that was a long time ago -- maybe they don't use
> those any more?). Anyone use something like this? Anyone use something
> gets rid of all the messing with silicon etc.? And, of course, something
> easy and inexpensive.

I have had good luck buying solid rubber stoppers at hardware stores,
drilling holes in them, and shoving in copper tubing cut to length. The
pre-drilled kind you mention also exist and would be more convenient, but
the hardware store I frequented when I bought a bunch of stoppers didn't
have any. The materials are cheap; I think the stoppers were about 30 or 40
cents each, and the copper tubing may have been a dollar or two a foot.
Bring a two-liter bottle, or whatever you use for CO2, to the hardware
store to size the stopper. More than one size will fit.

Drilling the stoppers isn't too hard. I held mine in pliers against a
workbench and used a power drill (sorry, I don't remember what bit size) to
drill all the way through. This created a rather rough hole and a lot of
rubber bits. I have since been told sticking the stopper in the freezer
makes it easier to drill, but I have not had a chance to try this. A little
water-based lubricant worked great for pushing the copper tubing through
the hole, and it makes a good seal. Cutting the tubing to length is easy
with a hacksaw or file. I found it useful to smooth out the cut end of the
copper tubing with a file, as the end was fairly rough after cutting. I
didn't want any burr poking a hole in my airline tubing!

I have only had one problem of note with this approach: Stretching airline
tubing over the copper tubing can be difficult, since the tubing I used was
slightly larger than comfortable for the (silicone) airline tubing I had. I
think the nominal OD of the copper tubing I used was .25 inch. This makes a
snug fit. The overall effect is similar to a predrilled stopper and glass
lab tubing; it's not nearly as easy to clean, but that's not so important
for our application.