"T i m" wrote in message
...
On Thu, 21 Aug 2008 21:15:48 +0100, "Spamlet"
wrote:


[1] My local Bambi dealer doesn't carry a spare valve so I've got a
bit of time to play. Also it seems a shame to throw away a perfectly
good, nicely machined and chromed brass fitting for the sake of a 10p
rubber valve. :-(


If you haven't already tried the suggestions - the fiddly part with rubber
being finding a piece as hard/soft/solvent proof etc. as the original; if
you can find a piece of the right stuff, I find an old set of lab
technician's cork borers often comes in useful for making washers/bungs
and
the like - you might find that your original can actually be *revived*.

Ooo, no I haven't tried anything as yet as I have been busy elsewhere
and was waiting for a call re how much a replacement was. Good news,
£19 for the part, bad news £50 minimum order and £20 postage!

We used to sell 'blanket reviver' for rubber printing blankets.

Ok

This was
basically a mixture of white spirit and a solvent like dry cleaning fluid
or
paint thinners. This swells the rubber and takes off the glaze. The
right
mix can make rubber double or treble in size or more with soaking. In
your
case you only need to soak it long enough to take out the ridge. Note
that
while the rubber is swollen full of solvent it will be weak so let it dry
to
a 'no smell of solvent' state before you put it back.

Oooo ..

Academic as you've probably finished by now...

Not at all, so, where do I find said potion please or are you saying
it is simply white spirit and dry cleaning fluid (or was that just a
guess / example) and we don't know the ratios etc?

All the best ..

T i m

Now you're asking, as I used to be in a lab, with plenty of different
solvents to try. For real spectacular swelling, chloroform was very good on
it's own. But, where a balance had to be struck between cleaning/reviving
and dissolving - plus the fire risk and toxicity and cost had to be
considered too - various mixtures were used. Most of ours tended to be cheap
white spirit, plus xxx, or cheap iso propyl alcohol plus xxx. It's a long
time ago now, but I think the blanket reviver was the white spirit plus
tri-chloro-ethane {'Trike': Which is similar to the per-chloro ethane -
'Perk'- they use in dry cleaners.)

These chemicals are only the 'preferred ones' because of the flammability or
toxicity of others that might otherwise be suitable (Carbon tetrachloride
having been the preferred dry cleaning solvent before safer alternatives
came along.)

In your case you are not so concerned about flammability and solvent abuse,
so you could try petrol for starters, or lighter fluid (though obviously,
these are not going to work if yours is the same sort of 'rubber' they make
fuel lines out of...). 'White spirit' itself is already a hotch potch
mixture that can be very variable, and some that you have to hand might
already be enough to swell the rubber a bit. Then there's nail varnish
remover - the 'pear drops' kind rather than the acetone kind. You may even
find that 'penetrating oils' like 'three in one' or 'plus gas', may do the
job, as we used to make a similar solution with the above mentioned 'trike'
with a drop of oil in: the solvent does the penetrating, and leaves a dab of
oil behind once it evaporates.

Take care if trying more severe mixes like cellulose thinners or paint
stripper, as these may dissolve your 'rubber' - rubber itself being a
blanket term for all manner of things. On the other hand, a brush
reviver/cleaner that contains methylene chloride (Dichloro-methane), might
be just the job.

See what you have around. Note that swelling may take several hours, but
check at first that your sample is not going to turn into a sticky mess.

Take care when experimenting: outdoors: no flames (Even the non-flammables
can break down into carcinogens on the end of a lighted fag for example.).

S