I have a 1 liter sintered funnel which has had a slow crack forming. Not even sure how it got there, but it's there. For awhile I just ignored it, but
today as I was using it I heard another cracking sound and noticed it has not only expanded, split in 3 directions, but it is now producing a leak
which is no go since this is almost exclusively used for vacuum filtrations. This is one of my most expensive pieces of glasswear and I really want to
save it if I can. So I figure an adhesive might work, it should stop the spread of the crack and seal the leak. Fortunately it doesn't need to
withstand heat, though if it could that would be great as I would like to dry it in the oven if possible. It does need to withstand at least water and
alcohols though, if I can at least use those I would be happy. Alcohols seem to rule out epoxies however which leaves me at a loss as that's generally
the best thing to use on glass. Are there any other options that might be more suited?
[Edited on 30-12-2016 by alking]unionised - 30-12-2016 at 07:37
You pretty much can't.
A good glassblower might be able to help you.
Using cracked glassware- especially under vacuum- is asking for big trouble involving flying broken glass and a fire.wg48 - 30-12-2016 at 10:15
As union suggests the crack cannot be healed (fixed) except perhaps by a glass blower and then only if it’s in a suitable location.
However you could cover the outside of the funnel in glass fibreglass reinforced resin all the way round and over the crack. The glass will need to be
well degreased first. That covering should stop the leak and prevent an implosion if the crack propagates to failure when under vacuum. unionised - 30-12-2016 at 12:16
Long version:
That will only work safely if you have a resin and fibreglass that has the same thermal expansion coefficient as the underlying glass.
Short version:
It's not safe. wg48 - 30-12-2016 at 14:20
Long version:
That will only work safely if you have a resin and fibreglass that has the same thermal expansion coefficient as the underlying glass.
Short version:
It's not safe.
I disagree. The fibre glass dominates the expansion coefficient of the fibreglass resin composite though its probably a soda glass with higher
expansion than borosilicate. In any case the adhesion to the glass keeps both in contact. In the unlikely event of an implosive failure the composite
would collapse relatively gracefully as it does not shatter in the same way as glass. It’s probably safer than an all glass funnel.
Of cause as in all vacuum work or any work with glass containers precautions should be taken to reduce risk of injury in the event of failure of the
glass. Eye protection for example. CharlieA - 30-12-2016 at 17:44
I'm not sure I would consider an implosive failure as an "unlikely event, especially under vacuum. Where is the crack on the glassware...in the stem,
where it would be exposed to the vacuum, or in the funnel portion above the frit? A local college/university chemistry department may have a
glassblower on staff who could repair your glassware, if it is possible to do so.alking - 31-12-2016 at 12:02
Thanks for the help guys. The crack is right on the frit. It breaks off into three, once more or less following the frit, one going upwards, and then
one downwards. I do happen to know a glass blower so I might ask him. I would imagine it's a simple fix, though I'm not sure if the frits would cause
an issue. If some of the frits are melted and lose their porosity it doesn't really matter I guess, so long as there are no larger gaps within them
and the majority work. For now I've put some super glue on it to preserve it from cracking further and do not intend to use it until fixed.
