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
> 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