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These times, more empirically arrived at, coincide.  I usually bake at 
128-129 f in an environmental chamber.

The thinner the tape, the longer I bake it, but not by a whole lot.

Steve Smolian

-----Original Message----- 
From: John Chester
Sent: Tuesday, April 07, 2015 7:34 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] More tales of woe from the tape vaults

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