 |
 |
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