I am certainly no expert but I have to agree with Chris. 3 months and still being able to leave a mark with Euro seems like there was another issue somewhere. I also agree with Crash. I have been able to leave finger prints in euro the next day when its cold out (I have never tried to leave a fingernail mark. I always test with a finger print.), but usually after a couple of days it is hard even without having to sit it in sun. I have had the opposite as Crash with UC though. It seems to take longer to dry IMO. I sometimes can finger print it 2 to 3 days later. But humidity can definately play a factor.