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Re: [ARSCLIST] Ampex 456
At 04:26 AM 6/17/2006, Steve Puntolillo wrote:
And Tom Fine countered:
> I'm not so sure about this. Ask Steve Puntollilo, who has
> successfully baked and transferred many
> sticky 2" tapes. As I understand it, 12 hours at the right
> temp will do it for any tape.
Ouch. Well not *any* tape. In all fairness to Tom and for the sake of
this group discussion, perhaps I should provide a bit more detail.
I've often wondered how to determine mathematically the right "formula"
to get the innermost 1/4" of tape in a 2" reel to bake for 12 hours at
130 F. And, if (and this is a "big if") we're indeed attempting to
evaporate moisture out of the tape, I've also wondered what effect the
thickness of the tape has on the path of escape for the moisture.
US Patent 5,236,790 -- and all text references are to playing the
tape on an Ampex ATR102. So this is 1/4-inch tape.
The process of this invention involves dry heat treat-
ment for relatively long periods of time. The tempera-
ture which has been found effective in the present in-
vention is at least 50' C., preferably at least about 54" C.
The time which has been found effective for the heat
treatment according to the present invention is at least
about 3 hours, preferably at least about 8 hours and in
some instances as long as at least 24 hours. The best
results are frequently obtained when the heat treatment
is continued for about 12 or 16 hours or more at a tem-
perature in excess of at least about 50" C.
It is desired that the relative humidity present during
the heat treatment be comparatively low such as 15% .
relative humidity or lower, which typically is ambient
relative humidity when ambient air is heated to the
preferred temperatures used in the practice of the pres-
ent invention.
(Note that I've checked and confirmed that an untreated 2" SSS tape will
leave oxide on static surfaces in the tape path *uniformly* top to
bottom. I think it's interesting that the condition is not perceptibly
worse nearer the tape edges.
This is the opposite of squealing tapes - those leave more debris at the edges.
In fact, not only is that the case, but
I've also found that the deeper into the reel one goes, the worse the
condition seems to get. Tapes that are trying to play near the outside
layers will often crawl to a stop as we get deeper into the reel. This
is the opposite of what I would expect to see happen.)
It is only the opposite if you think in terms of moisture penetration
-- which is what we've been led to believe.
It is immediately obvious -- and pinning and squealing also follow
this model to some degree -- when one considers the pressure of the
tape pack as a contributing factor.
Stuart Rohre at Univ of Texas has confirmed this, including the need
to re-bake halfway through a tape, but he is using 14" reels and
larger of instrumentation tape.
(1) Sometimes a tape won't make it all the way to playability on the
first try. Ironically, these tapes are more often 1/4" tapes than 1/2",
1" or 2". Don't ask me why this is.
I'm not good at following instructions: Why do you think this is the
case? Were the 1/4" tapes stored less well than the wider tapes? Have
you found any repeatable differentiation? Age? Wind tension? Wind
quality? Storage?
I have reason to
believe that a longer incubation period is necessary today over that of
a decade ago.
That is in keeping with my observations over the last seven years
that I've been doing baking. What I thought was a bad batch of SSS
from the Pacific Northwest required less baking than what I normally do today.
The amazing thing is that it *doesn't* take 40-60 hours to treat a 2"
tape (or batch of 2" tapes). If it's one 2" tape with an average case of
SSS, after 12 hours of incubation, 12 hours of slow cooling in the
incubator and 12 hours of standing at room temperature, the problem
should have yielded and the tape should be playable.
Another indication that there is more to this than meets the eye.
===================================================
Steve Puntolillo
Sonicraft Inc. - Analog and Digital Audio Services
http://www.sonicraft.com
===================================================
Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.