Cutting a demi john

Hi
I have a glass Demi-John, I need to cut the bottom off to make a bell jar
piece of equipment for experiments.
Some techniques scour the glass and then use a heated wire to shatter
across the score.
I have seen other methods such as filling the bottle with oil and inserting
a hot piece of metal, and the bottle should cut across the fluid line.
I have no idea if this method will work with Demi John's - has anyone got
any ideas how I could solve this problem?
Thanks
Anth

I hope you are not considering having a pressure differential across it.
I have seen the results of a gallon demi-john failing when then bung was
fitted too tightly and the pressure from the brew inside caused it to
explode, same could happen with a vacuum inside. If you do require one
to take a vacuum these are available from laboratory supply houses.

Anth wrote:

Hi
I have a glass Demi-John, I need to cut the bottom off to make a bell jar
piece of equipment for experiments.
Some techniques scour the glass and then use a heated wire to shatter
across the score.
I have seen other methods such as filling the bottle with oil and inserting
a hot piece of metal, and the bottle should cut across the fluid line.
I have no idea if this method will work with Demi John's - has anyone got
any ideas how I could solve this problem?
Thanks
Anth

Well I do intend to vacate the Demi using a vacuum pump as in
http://www.sas.org/E-Bulletin/2003-0...esAS/body.html
I'll probably end up transparent taping the bottle to stop it totally
shattering and I'll be wearing safety gear in case it does implode.
I've also looked into that cutting the bottle with oil - some say it works
some say it doesn't so I'm guessing it's hit and miss.
I think I will have to get a few Demi's to experiment on cutting.
(Once I have the Sputter chamber setup I can start making my own crude
optics.)
Anth

"David Billington" wrote in message
...
I hope you are not considering having a pressure differential across it. I
have seen the results of a gallon demi-john failing when then bung was
fitted too tightly and the pressure from the brew inside caused it to
explode, same could happen with a vacuum inside. If you do require one to
take a vacuum these are available from laboratory supply houses.

Anth wrote:

Hi
I have a glass Demi-John, I need to cut the bottom off to make a bell jar
piece of equipment for experiments.
Some techniques scour the glass and then use a heated wire to shatter
across the score.
I have seen other methods such as filling the bottle with oil and
inserting a hot piece of metal, and the bottle should cut across the fluid
line.
I have no idea if this method will work with Demi John's - has anyone got
any ideas how I could solve this problem?
Thanks
Anth

Forgot to say I've priced the commercial vacuum bells jars and they are way
outside my price range. (approx £100)
Anth

"Anth" wrote in message
.. .
[snip]

Having been asked about various methods a number of times, I finally ran
some tests on using a string soaked with kerosene and lighted. I tried on
small test bottles with and without scoring and found I got roughly the same
results: The crack went all the way around and was flawed by at least 1/4"
in one or more locations. That would mean quite a bit of grinding to reduce
the edge to an even surface. The bottle ends up a greasy black, which
washes off after getting on hands and everything. Alcohol does not work and
non-cotton string does not work. The bottle cracks as the flame goes out.
I have all the stuff to try low voltage with a nichrome wire, but have not
rigged it yet. Getting the wire to wrap the bottle all the way for cracking
without shorting where it completes the circle is my main concern.
Don't believe putting a hot iron in oil would produce enough of a shock
to crack the scored bottle although touching a hot iron to the score where
oil inside defined the stress line might work.
http://users.ticnet.com/mikefirth/bottle.htm my page on this topic.

--
Mike Firth
Hot Glass Bits Furnace Working Website
http://users.ticnet.com/mikefirth/hotbit47.htm Latest notes

"Anth" wrote in message
.. .
Hi
I have a glass Demi-John, I need to cut the bottom off to make a bell jar
piece of equipment for experiments.
Some techniques scour the glass and then use a heated wire to shatter
across the score.
I have seen other methods such as filling the bottle with oil and
inserting a hot piece of metal, and the bottle should cut across the fluid
line.
I have no idea if this method will work with Demi John's - has anyone got
any ideas how I could solve this problem?
Thanks
Anth

Anth wrote:
Well I do intend to vacate the Demi using a vacuum pump as in
http://www.sas.org/E-Bulletin/2003-0...esAS/body.html
I'll probably end up transparent taping the bottle to stop it totally
shattering and I'll be wearing safety gear in case it does implode.
I've also looked into that cutting the bottle with oil - some say it works
some say it doesn't so I'm guessing it's hit and miss.
I think I will have to get a few Demi's to experiment on cutting.
(Once I have the Sputter chamber setup I can start making my own crude
optics.)
Anth

"David Billington" wrote in message
...

I hope you are not considering having a pressure differential across it. I
have seen the results of a gallon demi-john failing when then bung was
fitted too tightly and the pressure from the brew inside caused it to
explode, same could happen with a vacuum inside. If you do require one to
take a vacuum these are available from laboratory supply houses.

Anth wrote:


Hi
I have a glass Demi-John, I need to cut the bottom off to make a bell jar
piece of equipment for experiments.
Some techniques scour the glass and then use a heated wire to shatter
across the score.
I have seen other methods such as filling the bottle with oil and
inserting a hot piece of metal, and the bottle should cut across the fluid
line.
I have no idea if this method will work with Demi John's - has anyone got
any ideas how I could solve this problem?
Thanks
Anth


I dunno if you have seen this link or not, but check this out:
http://lerch.no-ip.com/atm/ step 18, "Aluminizing."


-- "I can conceptualize what infinity is, but I cannot imagine it." MCJ 200406

So you are UK based?. I have that sputtering site bookmarked for
interest sake. I have a Nalgene poly carbonate vacuum bell I use for
vacuum dearating thing like silicon mould making compound and it does
what I want but still probably not much under £100 these days, I bought
it a few years ago. The glass ones were alot more expensive. Doing
things like sputtering could cause the polycarbonate one I have to fail,
it is susceptible to organic vapours and sputtering also might damage
it. I know a guy that has glass light fittings that are bell jar shaped
and there are garden cloches, these have much heavier walls than a
demi-john. I think the expense in the bought items is that they are
rated to do the job but still have to be treated accordingly. Have you
looked at this site http://lerch.no-ip.com/atm/ he covers mirror
silvering and other interesting stuff.

Anth wrote:

Forgot to say I've priced the commercial vacuum bells jars and they are way
outside my price range. (approx £100)
Anth

"Anth" wrote in message
. ..
[snip]

Thanks interesting site (I'm UK based).it is very useful to be able to make
your own optics as they tend to be expensive.
I am planning on using sputtering so I can experiment with electrowetting to
make my own dynamic fluid based lens - like the recent Phillips effort.
http://www.technovelgy.com/ct/Scienc...asp?NewsNum=49
I was thinking of using a plastic bell jar but I suspect the heat and
noxious chemicals generated in the sputtering process would damage it.
Plastic would be an ideal material though strength wise. Do you think a
garden cloche would be strong enough to withstand the 20 torr pressures
needed to coat the glass with metal oxide layers?
Sputtering targets are expensive (the one I wanted - Indium Tin Oxide was
£230 for a small disk of alloy) hopefully I can find a way around that too
or use a cheap and nasty method.
If all things fail I could use a ceramic jar but that means I can't watch
the plasma effects would is a bonus.
I think I will try that hot neo chrome wire and a dremmel to sand it down,
sounds like a plan to me.
Anth

"David Billington" wrote in message
...
So you are UK based?. I have that sputtering site bookmarked for interest
sake. I have a Nalgene poly carbonate vacuum bell I use for vacuum
dearating thing like silicon mould making compound and it does what I want
but still probably not much under £100 these days, I bought it a few years
ago. The glass ones were alot more expensive. Doing things like sputtering
could cause the polycarbonate one I have to fail, it is susceptible to
organic vapours and sputtering also might damage it. I know a guy that has
glass light fittings that are bell jar shaped and there are garden
cloches, these have much heavier walls than a demi-john. I think the
expense in the bought items is that they are rated to do the job but still
have to be treated accordingly. Have you looked at this site
http://lerch.no-ip.com/atm/ he covers mirror silvering and other
interesting stuff.

Anth wrote:

Forgot to say I've priced the commercial vacuum bells jars and they are
way outside my price range. (approx £100)
Anth

"Anth" wrote in message
...
[snip]

It's a good site - book marked it for future reference.
Thanks David/Mark.
Anth

"Mark Jones" wrote in message
...
Anth wrote:
Well I do intend to vacate the Demi using a vacuum pump as in
http://www.sas.org/E-Bulletin/2003-0...esAS/body.html
I'll probably end up transparent taping the bottle to stop it totally
shattering and I'll be wearing safety gear in case it does implode.
I've also looked into that cutting the bottle with oil - some say it
works
some say it doesn't so I'm guessing it's hit and miss.
I think I will have to get a few Demi's to experiment on cutting.
(Once I have the Sputter chamber setup I can start making my own crude
optics.)
Anth

"David Billington" wrote in message
...

I hope you are not considering having a pressure differential across it.
I
have seen the results of a gallon demi-john failing when then bung was
fitted too tightly and the pressure from the brew inside caused it to
explode, same could happen with a vacuum inside. If you do require one
to
take a vacuum these are available from laboratory supply houses.

Anth wrote:


Hi
I have a glass Demi-John, I need to cut the bottom off to make a bell
jar
piece of equipment for experiments.
Some techniques scour the glass and then use a heated wire to shatter
across the score.
I have seen other methods such as filling the bottle with oil and
inserting a hot piece of metal, and the bottle should cut across the
fluid
line.
I have no idea if this method will work with Demi John's - has anyone
got
any ideas how I could solve this problem?
Thanks
Anth


I dunno if you have seen this link or not, but check this out:
http://lerch.no-ip.com/atm/ step 18, "Aluminizing."


-- "I can conceptualize what infinity is, but I cannot imagine it." MCJ
200406

Have you got a source/link selling these garden cloches?
Anth

"David Billington" wrote in message
...
[snip] I know a guy that has glass light fittings that are bell jar shaped
and there are garden cloches, these have much heavier walls than a
demi-john. I think the expense in the bought items is that they are rated
to do the job but still have to be treated accordingly. Have you looked at
this site http://lerch.no-ip.com/atm/ he covers mirror silvering and other
interesting stuff.

[snip]