Re: [ARSCLIST] shellac and acidity

[Graham Newton <gn@xxxxxxxxxxxxxxxxxxxxx>]

Alain Carou
Bibliothèque nationale de France
alain.carou@xxxxxx wrote:

> I have recently inspected several shellac discs albums and observed that
> in some cases, the discs seem to have absorbed the acidity of sleeves. In
> the corners of the sleeves, colors have fainted, which is generally
> considered as a sign of acidification, whereas the part of the sleeves
> which is directly in contact with the disc keeps its original color. Does
> anyone know why, because I wonder if this could be a sign of chemical
> interaction between discs and acid paper ?

The interaction of the shellac disc and the paper sleeve seems less likely
than the oxidation of the paper of the sleeve as described in the following
comment:-

And David Seubert, UCSB, observed...
> > The portions of the sleeves that don't touch the discs are exposed to
> > the atmosphere and over time the atmospheric pollutants have discolored
> > the sleeves. The portions of the sleeves in contact with the record are
> > pressed tightly together, keeping out the air.

Atmospheric oxygen is probably the main culprit... heavily acidic sleeves
will become brittle with age and will break if bent...  I have seen many
examples of this.


And Kurt Nauck commented...
> > I also see records bearing an image of the printing on the sleeve. This
> > evidently is caused by chemicals in the ink which react with the shellac.
> > By the way, never write on a record sleeve with a magic marker - you will
> > see the same thing happen.

See item 1 below for an example of this... markers and some printing inks
contain solvents which will damage most record surfaces excepting vinyl which
seems most resistant.


Kurt also said...
> > What I have not seen (as far as I know) is any record obviously affected
> > by an acid-laden sleeve. Has anyone else?

Yes, and see item 2 below for an example of this problem.


Two related things that I have encountered are:-

1.  In the early '50's, a run of 12" styrene LP discs were inserted in newly
    manufactured paper sleeves which were constructed with a seam down the
    center of the sleeve, rather than a "fold and glue" at either edge.  The
    solvent in the glue used on the sleeve seam, presumably toluene or
    something similar, had not fully evaporated when the sleeve was placed in
    the outer cardboard jacket.  The remaining solvent had sufficient time to
    work on the surface of the styrene before it fully evaporated, leaving a
    misty band on one side of the disc which produced a double "swish" noise
    as the record rotated.  Fortunately, several of the discs were available
    for selection and good transfers were made using three of them.

2.  A series of 78 rpm lacquers of Brazilian pianist Guiomar Novaes were
    stored in a conventional multi-page album set over many years under moist
    warm climate conditions.  Upon looking at these discs, some were noted to
    be exhibiting an almost "black rash" blistering of the lacquer surface.

    This was puzzling since dubs from these very discs had been made by
    others with some success a number of years earlier, and the "black rash"
    did not exist at that time.  Upon examining the album pages, some
    discoloration and marks conforming to the location of the "black rash" on
    the discs were noted.  It appears that the album set was made of high
    acid content paper, and that the moist warmth of the storage conditions
    had released enough of the acid which contributed to the damage of the
    lacquer coating of the discs.

    Not all the discs in the set were damaged, and the ones that exhibited
    the problem did not show a uniform coverage of the "black rash". Some
    showed a splotchy occurrence, and the worst covered almost half of the
    surface on the affected disc side.  The worst cases were still playable
    but the damage produced a very high noise level and made listenable
    recovery of the material impossible.

The above is probably the most compelling reason to remove any valuable
artifacts from old sleeves and store them in recently made sleeves that are
known to be made of low or non-acidic paper.  Once the artifact is damaged,
it is less likely to be recoverable, as in the case of the lacquers
described here.



... Graham Newton

--
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