Originally Posted by cyclotoine
something that always struck me as odd is that you are supposed to apply the cement and then let it dry before applying the patch. Can anyone explain this to me?
The fragile bond is between the cement and the tube. You first make the cement set on the tube undisturbed to make that bond as strong as possible. Far more straightforward, by comparison, is the cement bonding with the patch side that is made out of less vulcanized rubber than the tube and has been just freshly exposed before it could collect any dirt.