Volatile loss

[John]

The rubber cement used for patches is extremely volatile and the
solvent will slowly leak out of the crimp of the metal tube container,
hardening the cement. I don't think this varies too much between
brands.

I choose to keep those metal tubes unopened and used only on the
roadside for emergency repairs, in case my spare tube also gets a flat.
When I get home, I patch the tube using rubber cement contained in a
screw top lid and pack the patched tube back into my saddlebag.

IME, once you open those small metal tubes, the life span decreases
substantially. I squeeze the container in my patch kit about once a
week to be sure it hasn't hardened.

John Forester recommends carrying rubber cement in a small, screw top
jar for patches (to minimize volatile loss). It's in the archives.

Cheers,
John

 

[[email protected]]

John McMurry writes:

> The rubber cement used for patches is extremely volatile and the
> solvent will slowly leak out of the crimp of the metal tube
> container, hardening the cement. I don't think this varies too much
> between brands.

> I choose to keep those metal tubes unopened and used only on the
> roadside for emergency repairs, in case my spare tube also gets a
> flat. When I get home, I patch the tube using rubber cement
> contained in a screw top lid and pack the patched tube back into my
> saddlebag.

> IME, once you open those small metal tubes, the life span decreases
> substantially. I squeeze the container in my patch kit about once a
> week to be sure it hasn't hardened.

It's the crimp as you said and don't let the screw top take the blame.
The smaller the remaining fluid, the less needs to evaporate and leak
out of the crimp.

> John Forester recommends carrying rubber cement in a small, screw
> top jar for patches (to minimize volatile loss). It's in the
> archives.

This is a misunderstanding of partial pressures of gases. A jar large
enough to hold a tube of rubber glue has enough volume to take up the
entire solvent in the glue tube as well as if the tube were left out
in the open. For a jar to hold such gases, it would also need to have
a metal gasket (one faced with aluminum foil for instance).

Jobst Brandt

 

[[email protected]]

John wrote:
> The rubber cement used for patches is extremely volatile and the
> solvent will slowly leak out of the crimp of the metal tube container,
> hardening the cement. I don't think this varies too much between
> brands.
>
> I choose to keep those metal tubes unopened and used only on the
> roadside for emergency repairs, in case my spare tube also gets a flat.
> When I get home, I patch the tube using rubber cement contained in a
> screw top lid and pack the patched tube back into my saddlebag.
>
> IME, once you open those small metal tubes, the life span decreases
> substantially. I squeeze the container in my patch kit about once a
> week to be sure it hasn't hardened.
>
> John Forester recommends carrying rubber cement in a small, screw top
> jar for patches (to minimize volatile loss). It's in the archives.
>
> Cheers,
> John

It must be strange to live in a place without goatheads.

 

[John]

[email protected] wrote:
> John McMurry writes:
>
> > The rubber cement used for patches is extremely volatile and the
> > solvent will slowly leak out of the crimp of the metal tube
> > container, hardening the cement. I don't think this varies too much
> > between brands.
>
> > I choose to keep those metal tubes unopened and used only on the
> > roadside for emergency repairs, in case my spare tube also gets a
> > flat. When I get home, I patch the tube using rubber cement
> > contained in a screw top lid and pack the patched tube back into my
> > saddlebag.
>
> > IME, once you open those small metal tubes, the life span decreases
> > substantially. I squeeze the container in my patch kit about once a
> > week to be sure it hasn't hardened.
>
> It's the crimp as you said and don't let the screw top take the blame.
> The smaller the remaining fluid, the less needs to evaporate and leak
> out of the crimp.
>

Good point.

> > John Forester recommends carrying rubber cement in a small, screw
> > top jar for patches (to minimize volatile loss). It's in the
> > archives.
>
> This is a misunderstanding of partial pressures of gases. A jar large
> enough to hold a tube of rubber glue has enough volume to take up the
> entire solvent in the glue tube as well as if the tube were left out
> in the open. For a jar to hold such gases, it would also need to have
> a metal gasket (one faced with aluminum foil for instance).
>
> Jobst Brandt

I'm not sure if I follow. Are you saying that at the top of the bottle
there will be enough volume for the solvent to separate and therefore
harden the cement because it is no longer in solution or; are you
saying the jar is incapable of containing the gas without a metal
gasket?

Why a metal gasket? Is it because the metal gasket is not porous?

Thanks,
John
(Originally, this was posted as a reply to another thread and then
somehow became it's own)

 

[[email protected]]

John McMurry writes:

>>> The rubber cement used for patches is extremely volatile and the
>>> solvent will slowly leak out of the crimp of the metal tube
>>> container, hardening the cement. I don't think this varies too
>>> much between brands.

>>> I choose to keep those metal tubes unopened and used only on the
>>> roadside for emergency repairs, in case my spare tube also gets a
>>> flat. When I get home, I patch the tube using rubber cement
>>> contained in a screw top lid and pack the patched tube back into
>>> my saddlebag.

>>> IME, once you open those small metal tubes, the life span
>>> decreases substantially. I squeeze the container in my patch kit
>>> about once a week to be sure it hasn't hardened.

>> It's the crimp as you said and don't let the screw top take the
>> blame. The smaller the remaining fluid, the less needs to
>> evaporate and leak out of the crimp.

> Good point.

>>> John Forester recommends carrying rubber cement in a small, screw
>>> top jar for patches (to minimize volatile loss). It's in the
>>> archives.

>> This is a misunderstanding of partial pressures of gases. A jar
>> large enough to hold a tube of rubber glue has enough volume to
>> take up the entire solvent in the glue tube as well as if the tube
>> were left out in the open. For a jar to hold such gases, it would
>> also need to have a metal gasket (one faced with aluminum foil for
>> instance).

> I'm not sure if I follow. Are you saying that at the top of the
> bottle there will be enough volume for the solvent to separate and
> therefore harden the cement because it is no longer in solution or;
> are you saying the jar is incapable of containing the gas without a
> metal gasket?

When the jar is sealed it essentially has a vacuum for the volatiles
in the tube, the partial pressure of that gas being zero when the jar
is capped. The next time it is opened, the evaporated solvent escapes
to be replaced by ambient air and the process repeats... it there is
any solvent left at that time.

> Why a metal gasket? Is it because the metal gasket is not porous?

Yes. Other gaskets (most soft materials are porous for this sort of
gas), like a mayonnaise jar with a plasticized paper gasket, leak like
a sieve for this stuff. As an example in packaging, club soda (Canada
Dry) is sold in clear plastic bottles that are porous for CO2. If a
bottle stays on the shelf for a longer time (few weeks from bottling)
it is nearly flat. Don't buys soda pop from stores with long shelf
life. I have had one liter bottles that were flat. A good manual
squeeze helps identify those.

I forgot to mention glue tube crimps when I talked to the REMA patch
guy at InterBike but then he wasn't even a bicycle guy, but from the
automotive division. I'm sure that if these tubes had a suitable
material in the tube where they are crimped, a crimp could be a solid
seal... some sort of Loctite.

Jobst Brandt