Re: [ARSCLIST] broken glass records--a possible approach to repair

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad


 I know that Chicago Albumen Works
> perfected a procedure for removing photographic emulsion from deteriorated
> acetate negatives.

----- the procedure used on glass plate negatives has been known for years.

I haven't heard about transferring emulsion from prints, I
> would be very interested in learning more about this.

----- it would involve reducing the adhesion between the gelatin and the
paper fibers


There is a company based
> in Germany that can actually split paper in half and then reaffix the
> deteriorated paper to a new backing.

----- actually you should call it a new core, because the two original outer
surfaces are there after the procedure. The procedure has several steps,
including pasting both outer surfaces to respective strong carrier sheets.
The important thing is that this paste is digestible by enzymes in a later
stage. Then the original paper sheet is split more or less in the middle by
suitable separation techniques, and both raw sides pasted (using a paste that
is resistant to the enzyme that works on the first paste) to one reinforcing
sheet. Suitable drying periods are to be observed. Then the new laminate is
treated with the digesting enzyme on both sides, the two strong carrier
sheets let go, and voila!, you have your new and strong sheet.

>
> Prior to creating my Master's program in the Preservation and Restoration of
> Motion Pictures and Recorded Sound, California State university, Chico, 1995,
> I worked for several years as an Art Conservator Assistant, where I gained
> experience in some of the skills for removing pigment from canvas.

------ so you will appreciate the above description

>
> Hopefully by talking about glass, the list was going to ultimately be able to
> get into to a discussion about ways to get recorded information off of broken
> shellac or broken glass records. If we utilize adhesive tape to hold the
> pieces of the broken record together then we are not making the disc stronger
> and the adhesives can in fact have some terrible effects.

----- actually, the glass sheet (which is more commonly aluminum) is actually
only the carrier for a fairly thin layer of cellulose nitrate laqucer that
adhered to the glass subsequent to manufacture (spin coating or dipping as
the case might be). The recording was cut into the lacquer surface, removing
some material. So a broken "glass" record is not at all amenable to the high
temperatures involved in melting glass. Since there is rarely an internal
tension in a broken "glass" record, there is no problem in fitting the pieces
perfectly together and hold them during transfer. The problem is that if the
pieces are stored for a long time in the broken condition, the adhesion
between the lacquer layer and the glass will diminish along the exposed edges
and air will enter. In broken shellac records there is tension in many cases,
because a break most frequently occurs when the record is not completely
flat, yet subjected to "flat" pressure. Those pieces are difficult to fit
together.

A glass negative that has been subjected to restoration by "re-backing" has
lost its property of retaining precise distance information (for instance in
aerial photography), and measurements can no longer be based on it. The same
would be if a whole sheet of lacquer could be floated in liquid and re-
deposited on a new backing. The distortions of the recorded surface would
create various types of wavering sound. Some of it would be treatable by time
base correction, because the signal is essentially one-dimensional.

Kind regards,


George