How Were 78 rpm Records Made?
The following is only a very simple outline of one ‘process
route’ by which 78s were made. There were many variants,
and
what follows is only my idea of the simplest ‘five step’ system… Even then,
what I say may be inaccurate. 8^)
The usual way of making large
quantities of 78s was the ‘five step’ process. There was a ‘three step’
process, mentioned below, but whether any companies actually used this system I
don’t know, though some small or very early ones probably did; also, larger
companies may have used this system for small runs, e.g. private recordings
where not many copies were required. But the five step system described below
was widely used. We shan’t get distracted with such minutiae as putting in the run-off groove, stamping the identity
into the various metal parts &c.; those topics are to be dealt with on
other web-pages. So let’s jump right in and start with Step One!
Step
One – The ‘Master’
Here is
a picture from not after 1931, of a wax cutting lathe and its devoted operator.
I have lifted it from a fascinating booklet entitled: ‘The Recording and
Reproduction of Sound’. A.G.D. West, M.A., B.Sc. Cantor Lectures, Royal Society
of Arts,
The main thing is that there is a turntable carrying a massive
circular wax blank. It is highly polished – you can see the operator’s
expression of stern determination in it! What would happen next, is that the
turntable would be run up to speed, the cutting head would be lowered onto the
wax the right distance from the edge, and immediately, the signal given for the
performance to commence. As the performance proceeded, a feed-screw would move
the cutting head across the rotating blank, and so a spiral groove would be cut
in the wax, carrying the sound in the form of a lateral modulation of the
groove. (Vertical and other cuts are outside the scope of this simple article).
So we have our ‘Master Record’. But being made of wax, our master
is delicate and easily susceptible to hazards, such as cigarette ash falling on
it, small insects becoming embedded in it, or perhaps just getting broken as it
is moved about &c., and so the next stage in the process would be carried
out as soon as possible.
(Moving unprocessed waxes about, however carefully handled &
packed, was always hazardous. The waxes made in the early 1920s by the Nordskog company in California, U.S.A., had to be sent by
rail to a processing & pressing plant on the East Coast of the U.S., as no
such facilities then existed on the West Coast. They would often arrive
distorted and unusable, due to the extreme heat of the deserts through which
the train had passed).
Step
Two – The ‘Matrix’.
The wax master is known as a ‘positive’, in that it could, in
theory, be played back on a gramophone. It would of course be destroyed in the
process, but the term ‘positive’ still holds. We need to render this wax into a
fixed & durable form, and that as soon as possible. Accordingly, it was
carefully brushed over with finely-divided graphite. Fortunately, graphite (a
form of carbon) can be very finely-divided indeed; and better still, it
conducts electricity. The coated wax is lowered into a tank containing a
solution of salts of certain metals, like Nickel, Copper & so on. An
electric current is passed through this bath, and, the graphite-coated wax
being the cathode, the various metallic ions in solution are deposited on it.
In time, this coating becomes relatively thick. We must not get carried away
and make it too thick though, because the increasing weight of the metal might
distort the soft wax, & that could in turn distort the metal image of it.
No: after just the right amount of time, learned by long experience, this
wax/metal ‘couplet’ is withdrawn from the bath, washed in clean water, and then
the metal is ‘peeled away’ from the wax. This durable metal part is called ‘The
Matrix’. It is a ‘negative’, and so cannot be played on a gramophone with a
normal needle or stylus. (Though they could, and sometimes were, played with a
forked stylus – but that again, is beyond our present scope). The wax master,
by the way, normally gets destroyed during this stripping process & can’t
be used again. Our matrix, being a negative, could be used to press positive
discs. In the earliest days, this was done, so we had just a fundamental ‘Three
Step’ process: Master – Matrix – Pressing. But there were many disadvantages to
this. One can only press so many discs before the ‘stamper’
wears out. The number you can get varies greatly, depending on many factors. It
might be several hundred finished pressings; or it might just be a few. That is
why the Five Step process, the one we are describing, came into existence.
We need another couple of steps to ensure a large and dependable
supply of records.
Step
Three – The ‘Mother’.
Our matrix is placed in an electroplating bath, and metals
deposited on it. As the matrix is quite strong, a fairly thick coating of metal
can be laid down. Afterwards, the two parts are very carefully separated. The
new part is called the ‘Mother’. It is positive: it could be played on a normal
gramophone. It is in fact, a precise replica of the original wax master, but
infinitely more durable. I had one of these once, a U.S. Victor side, and it
was about 3mm thick. I did play it, and even though it was made of metal, it
was quite noiseless – after all, the wax from which it was derived was
perfectly smooth. Now that we have a really robust version of our record, the
real work can begin! Of course, it would be possible to make another mother from our metal matrix,
perhaps several. So the matrix is carefully cleaned & stored away.
Step
Four – The ‘Stamper’.
Well, the next step is obvious, right? Back goes our mother into
the plating bath, and yet another metallic part is ‘grown’ from it. This one
can also be made thick and sturdy. Again, it is carefully separated from the
mother. This new part is negative – it could be use to press records. Which,
rather obviously, is why it is called a Stamper! Of course, a number of stampers may be made from our mother. That number varies,
but could be as high as 6, 8, 10 or even more. So after making the first stamper, the mother is cleaned & stored for future use.
Step
Five – The ‘Pressing’.
End of story, really. The stamper is
trimmed & put in the record press, opposite another stamper
which is for the other side of our disc. The labels are applied the right was
up, over whatever pins are provided to locate them and which also make the hole
in the middle of the record. I understand the ‘platens’ of the press were
usually heated by passing steam through them. Then, a suitably-sized chunk of
pre-heated compound – loosely referred to by us enthusiasts as ‘shellac’,
though only a small part of it is actually shellac – is placed in the middle of
the lower platen, and the upper platen is then lowered and presses the material
out nice and evenly between the two stampers. I
should have said, that a ‘parting compound’ is applied to the stampers before pressing, so that the finished disc will
come away from the stamper easily and completely. We
certainly don’t want odd tiny bits of our disc sticking to the stamper! These are called ‘pull-outs’, and are Very Bad.
Because not only will our disc have a couple of audible ‘clicks’ on it, but the
piece pulled out of our disc may remain stuck to the stamper
– and subsequent discs pressed will have the same defect! Perhaps when
listening to a vinyl stereo LP, you have heard a click from the left hand
speaker, followed one revolution of the disc later, by a similar clock from the
right hand speaker? That was a ‘pull-out’. There are many other hazards in
pressing discs too, but the above description, as we said, was only intended to
be a broad outline of the manufacturing process.
Unfortunately, we don’t have any illustrations of these
subsequent processes to put here. But a sound film is far better anyway, and
happily, there is a great one on-line. It dates from1942, & shows in great
detail the making of an RCA-Victor 12” (30cm) rpm record of ‘The Blue Danube’.
It lasts for 18 minutes, and is on youtube in two
parts:
http://www.youtube.com/watch?v=8xwe-Mt99Dw
http://www.youtube.com/watch?v=ZxhiUgK5gzs&feature=related
Some of the many variations in processing that we mentioned above
are encountered in the film. By 1942, RCA-Victor were
using ‘poured waxes’ instead of ‘cast waxes’, as hitherto. But their use is exactly
the same. There are other confusing terminologies, ‘mother-matrix’ for example.
Actually, I think some of these relate to the ‘seven step’ process.
Prodnose (irritably): I thought you said this was a
five step process? What is this new ‘seven-step’ process you suddenly mention,
without any warning?
Field:
Ah yes. Well. I was trying to explain making 78s simply.
Prodnose (snorting): Well, I followed your
feebly-expressed explanation of this five step process, and reluctantly admit I
found it – more or less – satisfactory! You say that a number of mothers may be
derived from a matrix, and that a number of stampers
can be derived from each mother? Am I not correct?
Field:
Yes.
Prodnose: Well then! A large number of discs can be
produced. What else could one want?
Field:
If you are an international company, you might want to issue the record in
another country, in case it sells even more copies.
Prodnose: Yes, of course we would. Well, send them
a stamper!
Field:
But stampers can only make relatively few pressings.
They would have to keep sending for more stampers.
Prodnose: Oh very well then! Send them a mother so
that they can make their own stampers.
Field:
If the record sold very well indeed, that mother might wear out and they would
need another one.
Prodnose (exasperated): Well then, send them a
matrix and have done with it! Then they can make mothers and stampers and pressings to their heart’s content; and the
profits will roll in!
Field:
There is only one matrix in the five-step process.
Prodnose: What! Are we to be denied profits? This
will never do! How can we get over this terrible problem? Speak up, quickly
now!
Field:
We must use the seven step process.
Prodnose: Why didn’t you tell me before? Yes, we
will certainly use this process! How does it work?
Now that my friend Prodnose has
temporarily subsided, let us sum up the five step process with a diagram…
As you can see, we have 1. The unique wax master. 2. The unique
metal matrix. 3. The several metal mothers. 4. The relatively many stampers; and lastly 5. the very many shellac pressings
from the stampers.
I think we’ll leave this page alone for now, and come back to the
seven step process later. If I can ever work it out! 8^) Still, the film was
instructive, wasn’t it?
In the meantime, I wish you all good fortune, and happy listening
to 78s!
Page
revised 1st February 2009.