On Monday, October 22, 2012 10:12:58 AM UTC-7, dgk wrote:
Each of my bikes has a little patch kit, containing a few patches,

scraper, and a little container of rubber cement. One bike had a slow

leak so I take out the tube, find the hole, scrape it, and prepare to

apply the rubber cement, but the little container of cement is empty.

I used it once, closed it, and it looks like there is cement in it

but, no there isn't.



I pull the patch kit out from another bike, and the rubber cement is

also empty. Very weird. Both little containers look full, but each has

been used once and there is no rubber cement left.



Apparently rubber cement evaporates after you open the containe even

if you close it tightly. And indeed, here is a comment from Amazon on

using something called Bestine:



http://www.amazon.com/Best-Test-Best.../dp/B000HF6UR0



5.0 out of 5 stars SOLVENT FOR RUBBER CEMENT November 10, 2011

By Victor J. Tennery

Amazon Verified PurchaseIN MY WORK I USE A CONSIDERABLE AMOUNT OF

RUBBER CEMENT - CONSTANT PROBLEM IS EVAPORATION OF THE CARRIER IN THE

LITTLE BOTTLES - RATHER THAN DISCARD, YOU CAN SALVAGE USING THIS

THINNER - CAN NOT BUY THIS ITEM LOCALLY - THIS SHIPMENT ARRIVED

PROMPLY AND WAS IN PERFECT CONDITION.



My neighbor had some rubber cement and I borrowed it and the patch

worked fine, but now I need to get more patch kits. I think they do

have some that don't use rubber cement but I don't know if those are

as good. At least now I'm warned - I've been riding with patch kits

that would be useless if needed.

Indeed, the volatile carrier for the rubber cement evaporates after the tube is opened and then left unused for a very long time. That is why you always carry an unused patch kit all the time. You put the one you used most recently in your garage tool kit and you can buy a LARGE tube of Rema rubber cement from your local bike shop. It too will evaporate but the tube is so large it takes years and years to become useless.

There are glueless patches but they do not work well. You're usually lucky if you can patch a tube so that you have a lead slow enough to get home before using your last CO2. If you have a full size frame pump it helps but as I said, glueless patches simply aren't any good.

What's more - tubes used to be nicely made and fairly smooth. Now their are mold seams everywhere so you have to be ultra-careful to really sand the area of the patch very well. Otherwise it's slow leak city.