It is possible that the ageing of a crystal is associated with the redistribution of the surface water monolayer, under the influence of the minute temperature gradient of an oscillating crystal. Some energy is dissipated in the quartz, so some gradient may exist. When a crystal is resting, the water may redistribute in the sealed package, but when run again, the water redistributes due to the temperature differences. Adsorbed water is in equilibrium with its environment, and, given time, will migrate along temperature gradients. It could be just one more mechanism in frequency drift. I would try using a reactive metal getter in the package to pick up any mobile water molecules. cheers, Neville Michie > On 10 Jun 2017, at 9:52 AM, Bob kb8tq <kb8tq@n1k.org> wrote: > > Hi > > You can’t quite process a crystal at 300C, but you can get close. > > Bob > >> On Jun 9, 2017, at 7:38 PM, Neville Michie <namichie@gmail.com> wrote: >> >> My memory of high vacuum work is that you need to pump for 4 hours >> at 300C to remove the water monolayer from glass. >> On top of the that water monolayer is another water monolayer that comes off more easily, >> and on top of that another……….. >> >> cheers, >> Neville Michie >> >> >>> On 9 Jun 2017, at 10:57 AM, Richard (Rick) Karlquist <richard@karlquist.com> wrote: >>> >>> >>> >>> On 6/8/2017 5:08 PM, Bob kb8tq wrote: >>>> Hi >>>> In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You very much do >>>> not want water running around inside your crystal holder… Helium is inert. >>>> Bob >>> >>> Exactly right Bob. The 10811 guys used to go nuts >>> about keeping water out of their vacuum system. >>> There were certain temperatures known as "water >>> points" at which some water was released. >>> The retained water was in spite of the temperature >>> already being above 100 degrees C (boiling). >>> It has something to do with monolayers of >>> water molecules not boiling away. >>> >>> Rick N6RK >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

Hi You do work pretty hard to turn the metal can into a getter. The other issue is that the adsorption and desorption rates are quite different. Once you get the “stuff” into a layer state, it takes a long time to get it back out. Much better to not have it there in the first place. If the precision crystal is being used in a TCXO, water has the nasty tendency to freeze. When it does, you get a frequency bump. That’s a difficult thing to compensate for. Does it occur at < -65 (you hope) or at -45 (you hope not) ? The practical approach is to get rid of as much of it as you possibly can. Bob > On Jun 10, 2017, at 12:22 AM, Neville Michie <namichie@gmail.com> wrote: > > It is possible that the ageing of a crystal is associated with the redistribution of the surface water > monolayer, under the influence of the minute temperature gradient of an oscillating crystal. > Some energy is dissipated in the quartz, so some gradient may exist. > When a crystal is resting, the water may redistribute in the sealed package, but when run again, the water > redistributes due to the temperature differences. > Adsorbed water is in equilibrium with its environment, and, given time, will migrate along temperature gradients. > It could be just one more mechanism in frequency drift. > I would try using a reactive metal getter in the package to pick up any mobile water molecules. > > cheers, > > Neville Michie > >> On 10 Jun 2017, at 9:52 AM, Bob kb8tq <kb8tq@n1k.org> wrote: >> >> Hi >> >> You can’t quite process a crystal at 300C, but you can get close. >> >> Bob >> >>> On Jun 9, 2017, at 7:38 PM, Neville Michie <namichie@gmail.com> wrote: >>> >>> My memory of high vacuum work is that you need to pump for 4 hours >>> at 300C to remove the water monolayer from glass. >>> On top of the that water monolayer is another water monolayer that comes off more easily, >>> and on top of that another……….. >>> >>> cheers, >>> Neville Michie >>> >>> >>>> On 9 Jun 2017, at 10:57 AM, Richard (Rick) Karlquist <richard@karlquist.com> wrote: >>>> >>>> >>>> >>>> On 6/8/2017 5:08 PM, Bob kb8tq wrote: >>>>> Hi >>>>> In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You very much do >>>>> not want water running around inside your crystal holder… Helium is inert. >>>>> Bob >>>> >>>> Exactly right Bob. The 10811 guys used to go nuts >>>> about keeping water out of their vacuum system. >>>> There were certain temperatures known as "water >>>> points" at which some water was released. >>>> The retained water was in spite of the temperature >>>> already being above 100 degrees C (boiling). >>>> It has something to do with monolayers of >>>> water molecules not boiling away. >>>> >>>> Rick N6RK >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com >>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.