[rollei_list] Re: Large Format film availability
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Thu, 1 May 2008 10:49:21 -0700
----- Original Message -----
From: "Jeff Kelley" <jlkphoto@xxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Thursday, May 01, 2008 9:48 AM
Subject: [rollei_list] Re: Large Format film availability
Richard, I don't follow your meaning re. "...the metal
work where it was
kept."
Jeff
Disc records are molded. The original recording is
electroplated to make a negative record (that is raised
areas instead of grooves). This can be used directly as a
mold for making one side of the record but where more than a
relatively few records are wanted it is itself electroplated
to make a postitive record (grooves again) which is in turn
electroplated to make the stampers or molds. Each metal
record can be plated several times. Usually, the original
"master" record is destroyed in the process of making the
first electroplate so, before tape the only copy of a
recording that was left was the metal copies. The stampers
were sometimes kept but in mass produced records were often
worn out. The first copy from the original master, sometimes
called a metal master but the terms vary, was usually
archived as was the first positive copies (sometimes called
mothers). These metal parts can be played. The positive
metal discs will play just as a normal record will, the
negatives or molds can be played by a using a special double
stylus. Usually now both are played by scanning the grooves
with a laser.
The original master was made of hard wax, in a cake
about an inch and quarter in thickness until about the late
1940's perhaps to some degree after that. Later masters were
recorded on blanks made by coating an aluminum plate with a
nitrocellulose mixture. These records are often called
"acetates" although they are not coated with cellulose
acetate. This type of record, also called an "instantaneous"
record because it could be played back directly, was first
made around the early 1930's but wax was preferred for
mastering for pressings for a couple of decades. The wax had
a very fine grain surface so was quite low noise. It took
some time for the coated records to catch up.
In any case, the metal parts, kept so that records could
be re-issued, will last practically forever if given any
sort of care in storage. Also they generally have much
better quality than the pressings made from them, at least
those from the 78 days. They have very low surface noise and
preserve the high frequencies that are often lost by the
pressing process.
Not all CDs of old recordings are made from the metal
work because the metal was often lost, especially for
smaller labels where it was kept by some custom production
house for a time and then discarded. The only copies of
these recordings are the pressings and CDs are made by
finding decent copies (one hopes) and playing them. Of
course, the quality varies all over the place.
The records sold are made by molding in a press. The
press has a negative record for each side of the disc
mounted in it. The platens have water pipes in them which
can carry hot water for heating and cold water for cooling.
The press is heated up, a label placed on the bottom and top
stamper (the name for the mold) and a "biscuit" properly
known as a pre-form, a small cake of pressing material,
placed in the middle of the bottom stamper. The press is
then closed and the biscuit is squeezed out under pressure
and heat until it flows into all the fine grooves of the
stampers. After a certain time the press is cooled down by
allowing cold water to flow until the pressing material is
set, then the press is opened and the record removed. The
timing of all this is important because if the press cycle
is to fast the pressing material will not flow properly or
set properly and the result is a noisy or distorted record,
or, in the worst cases, one where not all of the grooves are
reproduced (called non-fill). Since record pressing is piece
work there was a strong incentive to speed up production
resulting in poor pressings.
Even though automated or semi-automated methods of
record production were available for decades most of the
production remained handwork until the end.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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