[ARSCLIST] More about ET preservation (was "Comparable collections anywhere?")

[Eric Jacobs <ericj@xxxxxxxxxxxxxxxxxxx>]

There are three things that affect the condition of ETs:

1.  temperature stability (which causes plasticizer to exude
    - this is not "binder extrusion" as stated below, but
    exuding plasticizer - which then causes the nitrocellulose
    laminate to shrink and eventually delaminate)
2.  moisture (which causes the ester bonds in the castor oil
    plasticizer to break down into palmitic and stearic acid
3.  acidity (which accelerates the formation of palmitic and
    stearic acid - this is an autocatalytic reaction which is
    hard to stop once started

Hence:

A.  Environmental control is super important (stable temp and
    relative humidity (RH))
B.  Storage in acid-free (base buffered) envelopes (sleeves)
    after cleaning

Although glass ETs tend to be in better condition because
glass is an insulator, and this helps stabilize the disc
against temperature fluctuations - more so than aluminum -
glass is also extremely fragile.

If the discs are starting to form palmitic acid (which is
an autocatalytic reaction), it needs to be removed and the
disc resleeved in an acid-free (base buffered) sleeve for
long-term storage.  Leaving palmitic acid on the discs
will cause imprinting to the disc surface (a kind of
roughness due to accelerated exuding of plasticizer and
hence laminate shrinkage beneath the palmitic acid) which
then shows up as noise in future transfers.

Handling of ETs is also critical.  Finger prints are acidic,
and I often find palmitic acid formations where there are
finger prints.  If the finger prints date from the 1940s
when the disc was originally played, after you remove the
palmitic acid you will actually see such indentations/
roughness in the shape of the finger print with perfect
detail - a permanent distortion to the disc surface.  You
can hear these finger prints as noise in the transfer.

I cannot emphasize enough that ETs should always be handled
with gloves.

Cleaning technique, fluids, and equipment are especially
important with ETs.  For example, supporting a 16-inch
disc edge-to-edge throughout the cleaning and transfer
process (especially with glass) minimizes any substrate
deflection, and hence minimizes laminate or substrate
cracking (glass).  I have special platters that I use to
handle glass ETs - I move them in a sandwich to absolutely
prevent the possibility of breakage.  These platters also
serve as supports for cleaning and playback, which further
minimizes handling of the ET.  These special platters also
help me work with broken discs - I can flip a re-assembled
disc without having to assemble all the pieces yet again.

Other subtleties include the fact that nitrocellulose can
expand (rather permanently) in the presence of water,
particularly where there are cracks in the laminate.  So
minimizing fluid contact time is important.  Yet, palmitic
and stearic acid can be removed best when the disc is
flooded in the rinsing process.  Therefore a vacuum cleaning
machine like a Keith Monks is essential (this is what we
use, with the "Nuk" mod).  When you have significant
palmitic acid or the acid has formed into crystals, multiple
cleaning passes are required, only making a fast-drying/
vacuuming process ever more essential.

ETs are a very sensitive medium - sensitive to storage,
handling, cleaning, and transfer.  They are the least
"archival" of the disc mediums (when compared to shellacs
and vinyl).  This is why archival triage puts ETs near the
very top of the preservation priority list, even ahead of
most other media, including most tape and wire.

Playback of ETs with delamination requires a well set-up
turntable (good antiskate settings especially) in order
to track through any cracks in the laminate.  Just the
tonearm that we use costs about $2k - but we can pretty
much play any disc in any condition, even broken discs
or discs with missing bits of laminate.

The good news with consumer ETs is that there was less
plasticizer in these, and hence less palmitic and stearic
acid issues.  I generally do NOT clean ETs on a cardboard
substrate.  At most, I'll spot clean if there is significant
contamination, or rapidly clean with only slight amounts of
moisture.

Another useful accessory when working with ETs is a 150-200x
microscope with a graduated reticle so that you can measure
the groove widths and assess condition (wear and quality of
cut).  This allows you to know in advance the amount of noise
to expect, and can help you select the right stylus size
quickly without having to play the disc several times using
trial-and-error stylus selection.  Just because Side A of an
ET uses a 2.5 mil stylus doesn't mean that Side B will also.
Recording engineers will sometimes make adjustments to the
cutting parameters between sides, and a microscope will
catch these changes.

Naturally, if your ET collection is pristine, then much of
the above issues become minor.  But most of the ETs that I
see have some mix of problems.

If you haven't guessed, ETs are one of our specialties...

Eric Jacobs
Principal

The Audio Archive
tel:408.221.2128
fax:408.549.9867
mailto:EricJ@xxxxxxxxxxxxxxxxxxx



-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of Klara Foeller
Sent: Tuesday, September 12, 2006 12:59 PM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Comparable collections anywhere?


Roger -
I have three large ET collections (16" Electrical Transcription Disks).
I estimate a total of 2000+.  My observations are as follows:
1.   Stable, climate controlled environment and proper upright storage,
matters more than materials.
2.   Lacquer on glass or aluminum is better than cardboard. Glass seems
to have held up best.  (Cardboard was a wartime compromise.)
3.   Professional recording blanks are higher quality and are usually in
better condition than home consumer blanks.  I just took in a small
collection of home                   recordings on a variety of blanks
and the same holds true, glass core disks are in the best condition, but
there are very few in the collection, most are on cheap           (thin)
cardboard.
4.   There were different formulations and combinations of core
material, binder and surface lacquer that seem to be "label" or
manufacturer specific, although I've            noticed
labels/manufacturers changed formulations over time.
5.   My biggest problems are breakage, warpage, "crackle" and binder
extrusion.  I haven't tried to reproduce badly damaged recordings -
either broken or those           with crackle and warpage.
6.   I have successfully cleaned disks with heavy binder extrusion and
had them digitized by a vendor under a small private grant.  Results
were fantastic.
7.   In all three of my collections, the ETs are the original format -
not duped from tape.

Although I was very happy with the results of the digitization completed
by an out sourced vendor, I will now be doing these transfers in-house.
I am fortunate in having a couple of variable speed ET turntables, which
have had a standard RCA plug installed so it can easily be connected to
my digital break out box or my analog router.  These period,
professional turntables can be fitted with specialized needles
appropriate to each type of disk, and can play from the inside out, as
well as outside in.  Mine were donated.   You might want to consider
setting youself up with an in-house capability. Check around your local
radio stations and recording studios and see if anyone has one to
donate.   In the long run any transfer project will cost less and you'll
have better control.  Not to mention the safety of the disks.  Saves
wear and tear if you aren't shipping them all over the place.

I have other information and recommendations.  Feel free to contact me
off list.

Klara Foeller, Curator
Moving Image & Sound Collections
Missouri Historical Society - St. Louis
314 746-4513


Roger and Allison Kulp wrote:

>Do all lacquer discs flake and peel over time ? I have some from RCA,
Columbia,and EMI,from the late 30s,and 40s,that are still as good as the day
they were made.OTOH,I have seen cheaper home-recorded jobs,where most of the
surface has flaked off.So some are more archivally stable than others.Does
this have something to do with better quality materials,or the fact they
were made at commercial pressing plants ?
>   What is the oldest lacquer disc that anyone has come across that is
still playable ?
>                Roger Kulp
>
>"Richard L. Hess" <arclists@xxxxxxxxxxxxxxx> wrote: This sounds like an
important collection.
>
>Karl made a very important point about these perhaps being the best
>version of the collection. However, some portion of the last ten
>years of these _may_ have been mastered to tape and then transcribed
>to disc for distribution.
>
>While you can do a lot worse than pristine ET discs, it would be
>interesting to know if the original master tapes survive in your
>collection or in another collection. I wouldn't waste too much time
>looking for that tapes as the ETs should be fairly close to the
>tapes, but if a few hours cause the tapes to surface, then evaluating
>the tape vs. the disc would be useful and transferring the one that
>generally sounds better.
>
>Neither tape nor lacquer disc is really archival, so one of these
>should be transferred soon. The lacquer discs are probably the
>priority even if tape is found.
>
>Cheers,
>
>Richard
>
>
>
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