On 4/7/15 5:26 PM, Richard L. Hess wrote:
> On 2015-04-07 3:18 PM, Eric Jacobs wrote:
>> 2-inch tapes with sticky shed may not respond as well to baking as
>> 1/4-inch.
> That is true in the sense of in the same or similar time frame.
>
> I don't think there are precise formulae for predicting the time 
> either to achieve thermal equilibrium or to achieve moisture 
> equilibrium in a tape pack. Vos (1994) inspired me to develop a rule 
> of thumb that moisture equilibrium appears to take 1500 times as long 
> as thermal equilibrium in a one-inch tape, based on my extrapolations 
> from his curves.
>
> We have long suspected that the width of the tape was a large modifier 
> of this ratio. I based my estaimate on Vos's graphs which seemed to 
> indicate that a 1-inch tape pack, might achieve thermal equilibrium 
> might in 100-200 minutes while it might take 100-200 DAYS to achieve 
> moisture equilibrium. I felt that a factor of 1440 implied far too 
> much precision in the calculation, so I rounded it to 1500.
100 days to achieve moisture equilibrium?  That must not be required for 
curing sticky-shed audio tapes, because they don't need to be baked 
anywhere near that long.  I recently asked Steve Puntolillo (who 
regularly bakes 2" audio tape) how long he baked it.  He said he gets 
clean playback on most 2" sticky-shed tapes after baking for 2 days, and 
cooling and resting for 1 day.  My recent experience with 1/4" Ampex 407 
is that one day bake and one day cool and rest is almost always 
adequate.  However, both Steve and I have observed that the required 
bake time has about doubled compared to a few years ago.

-- John Chester