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 at this link:
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?
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.
Also slightly revised 4th January 2014 (New YouTube link)..