Text 15162, 77 rader
Skriven 2007-01-06 17:12:56 av Glenn Meadows (1:379/45)
  Kommentar till text 15153 av Frank Haber (1:379/45)
Ärende: Re: Me in Print!!!
==========================
From: "Glenn Meadows" <gmeadow@comcast.net>

The 1973 tape was a totally different problem.

In the late 70's, into the early 80's, formulation of tape was rapidly changed
due to EPA demands.  The old stable formulations of tape had to be changed to
remove carcinogens released during the actual manufacture of the tape, and both
Ampex and 3M were give 90 days to make changes, or stop production.

That lead to shortages of tape for about 9 months, as each company scrambled to
adjust tape formulation and mfg procedures that had been tweaked and micro
tuned over years of production.  The initial new formulations appeared to work
well, but about 12 years later, a horrible problem appeared in tapes made
during the first 3-4 years of that span, the binders started to break down due
to absorbsion of moisture, and what was a solid coating, started to turn to
gooey paste.  As you played the tape over the heads, the oxide would start to
scrape off, and pile up on the edges of the heads or guide.  if the tape
machine had a tape lifter to hold the tape off the heads, it could literally
scrape a layer of oxide off the tape.  Then, when you stopped, the glob of
oxide would be deposited on the tape where you stopped, thus making that spot a
real "klunk" spot.

It was someone at Ampex that came up with the solution, bake the tape.  The
initial device, was a cardboard box, that used 2 hair dryers on low, with slots
cut in the top of the box, and used a meat thermometer to monitor temperature. 
Keep it at 135 degrees for 8 hours per 1/4" reel in the box. Separate multiple
reels so air could circulate.  The idea was to drive the moisture out of the
tape.  It worked.  A new cottage industry sprang up, baking tapes.

We bought a round Sunbeam convection oven, that also had "extension rings" that
allowed you to make it taller. We could handle 3 2inch reels of multi-track
tape at once.  We charged $25/hour for tape baking, and saved many a project
for people.  One of the later ones, was the Linda Rondstadt Live orchestral
project.  Dual 24 track recordings, 20 reels of tape, took days to bake.  After
baking, the tapes will keep their form for many weeks.

About 4 years later, both AGFA and BASF suffered the same fate, and the same
corrective action was required.

There are thousands of tapes out there from that era that have to be baked to
extract their music.

There also is a generation of Ampex 456 that has a different problem.  In the
making of the tape, the "calander" the oxide side, to make it smoother (shiny).
 At one point, in the strive to increase the output of the tape, they over
calandered the tape, and on Studer, and some of the Ampex ATR-100 machines,
that tape would grind to a halt, not because of sticky goo, but because of the
too shiny.  Have you ever tried to slide 2 pieces of glass against each other? 
That's what would happen.  The heads on the tape machines got smoother and
smoother, and the tape being so smooth, would be like 2 pieces of glass. 
Nothing more odd, than seeing a $50,000 tape machine trying to move tape over
the heads, pinch roller engaged, and the tape is frozen in place.  The resolve
for that one, was ADD moisture to the tape.  We'd place a cloth that was damp,
just touching the tape as it entered the head block section, to "wick" the
tape.

Then there's the old acetate tape from the 50's and 60's. Those tapes will curl
away from the heads when you play them, as well as being super brittle now. 
I've taken many acetate tapes and had to splice them back together when they've
split/snapped during rewind. Or the splices have dried out, and come apart as
the tape is played.

Too much to remember...yikes....

--

Glenn M.
"Frank Haber" <frhaber@N0SPMrcn.com> wrote in message
news:459ff69e$1@w3.nls.net...
> (Gummy analog masters, baking)
>
> Ten years ago, 1973 Ampex 406 was the worst offender.  Has the rot now
> extended to 456, Agfa, BASF and Scotch?  I've never baked, or mothered, a
> 2" master.  Any different from 1/4", except for the time in the oven?

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