Pressing Matters
The Production of Phonograph Records


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The Lacquer Channel
The Cutting Head
The Recording Stylus
The Lacquer Disk
The Disk Cutter
The Chip
Cutting The Disk
Speeds, Grooves & Record Sizes
The Plating Plant
Plating The Lacquer Master
Negative Metal "Matrix" To Positive "Mother"
Stamping To Pressing
Of Shellac And Wax
Vinylite And The Shellac-less Shellac
The "Waffle-Iron" Record Press
Multi-Speed Operation
Milling And Mixing



Making a metal stamper that will actually mold records from hot shellac or plastic is essentially a multiple plating process - depositing metal upon metal in the traditional manner, by means of an electric current that transfers metal through a plating solution directly to the surface being plated. At this point record making is surrounded by tanks. Rows and rows of containers filled with poisonous-looking green and yellow and orange liquids, some steaming, some sloshing about, as objects are swished through the depths - this is the necessary scene, and by its very nature it is not likely to be housed in the company's plush front offices! Plating plants are off in far city corners, or housed in strictly industrial park areas.



If we are to make an actual metal impression of the lacquer record; we must either flow on a metal and let it harden, or plate it on cold. The first process obviously being impossible (lacquer is a soft, highly inflammable plastic!), some form of plating is the only answer. But how to plate metal onto a non-metal?

Strangely, it's easy, and a number of methods have been used. The oldest, when master records were cut into wax blocks, was to apply an extremely thin coating of graphite, a form of carbon that we know as pencil lead, which conducts electricity. To this coating, thin enough not to disturb the record groove shape unduly, one could actually plate metal, which would take on the shape of the record grooves. When enough metal had been backed up on the plating, it was an easy matter to strip it from the wax and the graphite, leaving a mold of metal.

Three ways are used to get the first microscopic layer of metal onto the lacquer. Silver spray is the newest and trickiest. Still used, also, is the silver pan bath, similar in its chemistry; it takes longer, and is not as accurate or trustworthy. The gold-sputtering process is more complex, but not necessarily better than the silver-spray, and possibly less uniform. The silver methods are more widely used. In the intriguing gold process, the master is mounted in a vacuum chamber between a gold cathode and an anode. A 3000-volt direct current creates a glow discharge, as in a vacuum tube; molecules of gold are deposited on the lacquer by secondary emission, leaving an extremely thin layer similar to the silver layer in the other process. Upon this molecule-thin layer of gold, the usual plating is done.

Lacquers are treated in more ingenious ways, to give metal coatings at first only a molecule or so thick. The most dazzling to watch involves silver nitrate and a simple spray gun. The lacquer surface is "sensitized" by being dipped into a solution of stannous chloride which is washed off in a water spray, leaving a very minute coating. Silver nitrate solution is sprayed at the disk-and, lo, the dead black grows into a perfect mirror of silver in a few seconds. Silver has been deposited in an extremely thin layer by chemical (replacement) action, the stannous chloride acting as a catalyst to promote the process. The newly silvered disk is washed (washing is almost a fetish in plating plants) and moves on to its next treatment.

From this point on, the objective is to build up a solid metal backing on the thin silver coat. This may be confusing, since this "backing" is actually being deposited on the front of the original disk. Remember, that we are making a negative mold, its surface now of silver, in direct contact with the lacquer surface and facing away from us as we look at the record. We are really looking at the silver from the rear, and we are about to add more metal to that rear in order to stiffen it. The original record will eventually be stripped away, leaving the other side of the silver, the facing-down side, as our mold.

The beginning of the build-up of this metal backing support, a layer of very fine-grained and delicate copper or sometimes nickel, is laid down slowly on the silver surface we have just made. It is fine-grained in order not to disturb the tiny groove patterns and to hold them accurately in place. After this, a more coarse grained metal can be piled on, although in some plants, another layer of fine grained "pre-plating" was added first, to be doubly sure. The coarse coating is desirably much faster, since at the slow fine-grain pre plating speed, it would take perhaps weeks to build up a strong enough layer of metal. One company used special rotating disk anodes that swish around close to the surface of the metal record and do the plating job to required thickness in a few hours. Other much slower systems use the usual immersion tanks with moving arms to swish the contents about.

Enough metal is thus put on the back of the silver surface to support it rigidly. Whereupon, with a quick blow of a special hammer and perhaps a wiggle or two of an inserting tool, the entire silver-copper mold breaks free from the lacquer, and we have a negative in metal, the back side or down-surface of the silver a mirror-image the original grooves. The lacquer is usually damaged in this separating process and cannot be used again; so the new metal negative, or "matrix", is now the only form in which the grooves exist. Being a negative, the grooves become sharp ridges with flat valleys between.



This metal negative or "matrix" can be used to stamp out actual records, and occasionally this is done for small run manufacturing requirements. Since it is now the only existing copy of the original lacquer disc, in most cases it is used to produce a "mother", in reality, a positive metal record that can actually be played for testing purposes. Playing is not this mother's destined role and instead, the mother is submitted to another plating operation much like the first, ending in another metal negative which is the desired "stamper". Since the mother, unlike the fragile lacquer original, is made of metal, it can be re-plated many times over, producing negative after negative in metal, all identical with the first. We now have a source of negative offspring stampers, each of which can press out as many as a thousand or so actual finished records. Multiple mothers can be made from the original metal matrix so multiple identical mothers can be sent to other pressing plants or countries for their production requirements, and thus huge quantities of records can be produced in a very short time if need be, all with exactly the same quality level of the release pressings in the originating country or plant.

But back, briefly, to the plating room and our original metal matrix one- of-a-kind negative, its silver surface just neatly stripped from the lacquer. The first step in preparing for the creation of the mother is to remove the silver that now contains the direct groove Impression. Remember again, the silver was next to the lacquer... it went on first and is on the bottom of the plating that was subsequently heaped on top of it! Strip the lacquer away, turn the entire plating over, and you are looking at the other side of the silver, the down-side, that was next to the original lacquer grooves. Removing the silver coating is necessary because it would quickly oxidize and corrode in the air. Fortunately it is a molecule-thin coating, and the underlying harder metal has virtually the same sharp image as the original. A swish or two of chromic acid takes the silver away faster than it was deposited by spray in the first place.

With the silver off but the groove image still nicely metalized in this negative matrix, the whole plating process is repeated to "grow" a new image, the mother. But first, before plating, a separating solution is applied to the surface, so that, though metal will plate on metal, it can be stripped off later on, otherwise the entire thing would become a useless solid metal block.



There's a lot to be done to this fourth-generation stamper (positive original; negative metal matrix; positive mother; negative stamper) before the fifth and final generation, the release pressing that you will buy, can be produced. A hard but ultra-thin chrome surface must be plated on, for wear. Then there's the little matter of that hole in the middle, a very crucial business, not to mention the stamper's rear side, which must be shaved to the right thickness to fit the presses, and the outside edge which must be trimmed to size. The rear surface is machined away in a lathe operation where a precision gouge neatly scrapes a spiral track from the outside of the back, right to the inside, shaving off all the irregularities, leaving a mirror-bright flat backside. The edges trimmed, the stamper then goes to the centering machine.

If you are mathematically minded, you may appreciate the problem involved in finding the exact center of a spiral, especially when that spiral is made of wavering, wobbly Lines. Impossible! (Don't be confused by the disk itself-the center of the disk is not what we want.) Of course, the original lacquer had its hole in the exact center. The hole was what determined the original spirals. But unfortunately that hole, spread and stretched in the plating, cannot be relied upon. One must start anew and make a new hole.

How? Simply by trial and error. As we all know, to our pain and distress, the slightest deviation from a perfect center hole is fatal to recorded music of any sort. Yet the man who makes the hole in the record does it just the way you and I might... by playing the grooves with a sort of needle and watching the way the arm wobbles back and forth. He is helped, though, by a magnifying device that reads the arm's motion on a big dial; when the dial's wobbles become reasonably uniform, he brings down a punch that cuts the hole. And frequently, with the record having slipped, it is in the wrong place! The first man I saw at this job tried one master five times, and gave up; it was off-center every time in a different direction. Every single record ever made goes through this trial-and-error search for the perfect hole, no better way having been found to do it.

As soon as the master has its hole, it loses it. Another punch knocks out a big disk a couple of inches across from the middle to fit the center of the press. But the disk's position is exactly determined by the small hole, and so the essential information is preserved, the final hole in the record to be made in the actual pressing according to it.




Wax and shellac are terms we still associate in popular language with phonograph records. But not only has wax vanished as a medium for the actual cutting of records; shellac, too, is gone in favor of the synthetic plastic products.

For that matter, no record was ever made of pure shellac. The old-style 78 rpm "shellac" record was made of a molding material that we now call a thermoplastic ("melts with heat"), in which shellac was greatly extended by assorted neutral filler materials, among them the carbon black which gives the black look to most records. Formulas for record material were and still are highly controversial and highly variable-quiet surface, hardness, resistance to breakage, and other features being more or less at odds with each other. Whatever a record material is compounded of, it must be both hard and smooth in the cold state, and capable of melting or softening to the proper degree with heat.


Pure shellac would never do. It would be as brittle as thin glass. Yes, record shellac is, indeed, the same material as the shellac we find in the familiar varnish. Shellac or "lac," its more correct name, is a natural resin, not unlike the gummy substance found on pine trees. Its source, however, is the Far East, where the female of a bug that infests certain trees of sorts unknown in the West, coats itself for protection with the gummy stuff. Ground-up insects constitute a good part of the first shellac product, but various stages of purification are represented by our orange and white shellacs, which are no more than simple alcohol solutions of lac. This same substance serves as a binder for the assorted ground-up an powdered fillers that have made up various phonograph record materials these many years, the percentage varying according to the formula.

An interesting economic situation arose due to the geographical location of the lac-producing bug and its special tree, largely within what was the British Empire before Indian independence. Britain controlled the world supply of lac, and all phonograph records made outside the Empire depended upon British exports. It is no coincidence that English shellac records have long been known as the finest made. Whether more shellac was used than in other formulae is a question. Better grades of lac (which, being a natural product, cannot be absolutely standardized to one grade) are more likely the answer, since the optimum percentage is not very high. Much of the quality of a shellac record was also due to the degree of uniformity and fineness of grain of the neutral filler or extender that was bound together by the lac.



Though millions of so-called "shellac" records may be found in the USA and Canada, a large number of them contain no natural shellac at all! Instead, the binding material is vinylite, a synthetic resin plastic made in the USA by the company that developed the first important thermosetting plastic, bakelite, in the early 1900's. Now the British must buy vinylite from the United States. The later-day American "shellac" record was a part-vinylite disk, the extender, including the traditional ultra-fine powder, carbon black, being much as it always was, the binding material vinylite instead of lac.

The plastic "unbreakable" records were also vinylite-made. Unlike natural lac, this new plastic is flexible, yet strong and hard enough to be used in its pure state as a material for record making. Pure vinylite is not cheap, and, strangely enough, a certain amount of cheap extender or fill mixed with the pure product produces a record claimed to be even better than one made with vinylite alone. Just how far the addition of other material should be carried for best results, and what materials should be used (discarded records ground into powder, for instance), are matters for complex economic calculation. The majority of top-quality LP records, shiny black in color, long-wearing, flexible, are made with a large percentage of vinylite, but significantly less than one hundred per cent. Many fine records were made of the pure product, dyed red for looks, as were many radio transcriptions - not a little of the appeal being in its attractive appearance, its window-clear transparency.

But the simple fact is that we bought records that varied from the pure vinylite type, always transparent, often colored, through dozens of formulae containing less and less plastic, more and more of the various extenders, until we reached the shellac-less "shellac" record of the popular 78 rpm standard-speed hits and a few remaining classical albums. Since that record was easily comparable to the best of the earlier true shellac disks, it is clear that in the synthetic plastic we had a material of enormous economic flexibility, adaptable to all sorts of technical and economic requirements in the record field.

The percentage of vinylite in a record is not the final measure of its value to you. The actual materials used to extend the pure plastic are of very great importance, as is the uniform fineness of grain of those materials. A small addition of carefully chosen materials, including the ultra-fine carbon black, actually improves the basic vinylite's properties for record making, and that is why most high quality plastic records are opaque black. Beyond this, while sound quality and/or wearing quality may decrease, the variations are enormous. Each brand must be judged for itself on these bases, and of course, in relation to the price charged and the value of the record's sound. At least one expensive brand of small-company records was known to use a material with very decidedly sub-standard wear properties, though the associated hiss when the records were new was barely audible.



After the half dozen or so processing steps that occur between the original recording and the final metal negative stamper disk comes the final operation, the making of the actual record.

The pressing process is surprisingly simple in operation. The kitchen waffle maker comes to mind, and indeed the pressing machine's working parts are not so very much larger than a good, solid waffle iron, though the accompanying complications are something else again.

Let's take the waffle maker as a beginning and do a mental conversion job on it. The basic structure is precisely what is needed for record making... two similar molds, both heated, mounted face to face with a hinge at the rear so that the machine opens up facing you. Enlarge these two molds to record size; provide, instead of the waffle pattern, means to hold two record stamper disks, one below and one above (fastened in by their centers and around the edges), and you have the beginnings of a record press. Waffles cook by electric heat; here we need a major substitution in the form of an elaborate channel system behind each stamper to allow first a sudden heat, using super-heated steam at three hundred degrees, then quick cooling by cold water, all of which must be controlled by the opening and shutting of appropriate valves - and automatically, since no human operator could maintain the exact desired cycle of hot and cold that produces the perfect record. With this we approach the complete, if hypothetical, conversion of waffle iron to record maker.

The simplest record to make and the most common is the solid disk, of one homogeneous material all the way through, though the more complex records, such as Columbia's old laminated disk, go through the same presses. Record and label are bonded together in the pressing. The operator of a pressing machine has beside him a hot tray, precisely like a hamburger grill in a fast food restaurant, on which is placed a dozen or so "biscuits" - rectangular blocks of material, (shellac or vinylite) about half the area and two or three times the thickness of the final record. The biscuits soften up on the hot plate until they are of the consistency of a soggy piece of fried mush, just about movable in one piece, and no more. With the press open like a waffle iron, a sandwich, first a label, then a biscuit, then another label is placed in the press, and the top lowered, waffle-wise. The automatic system then takes over unobtrusively; steam heats and flows the plastic material into every tiny groove; at the predetermined moment it is replaced by water, and the record is instantly hardened. The record is lifted out, and the next one is ready to go in.

The occasional reversal of labels on records can easily be understood, since the operator of a pressing machine must put the labels and the biscuit into the press by hand. Nothing is easier than to reach for the wrong pile first, or to put the right pile in the wrong spot in the first place. My wonder in watching these operations was aroused by the positively staggering opportunities for confusion that were present - what with hundreds of piles of labels, biscuits of various sorts, unattached stampers, loaded presses, all looking more or less alike, and easily interchangeable. Yet in almost every case, the right pair of stampers connects with the proper pile of labels and the correct biscuits to produce an acceptable record that reproduces the music it says it will. Drastic mistakes are altogether rare.



After coming out of the hot press the newly made record has its ragged edge neatly trimmed by a circular cutting device (something like a revolving can opener) and is then passed on for inspection.

If you think that perhaps record companies are less careful than they should be, witness the inspection process for yourself. Records are rejected by visual inspection and by actual playing checks. It's enough to say that a significant quantity are rejected - large bins of rejects, returns and cut-outs wait to be fed to the elaborate machinery that reduces these masses of unsatisfactory disks to chunks, and then to powder for recycling into more records. Visual inspection is done by workers who look closely at every disk that comes to them on conveyer belts, sorting out the duds. The supplementary playing-out-loud of a sample record every so often catches most faults that may have developed in a stamper before it has pressed too many bad disks. Considering the numerous possibilities for trouble in this whole mass-production operation, I'd say that consumers were reasonably well protected.



If you always assumed that LP and 45 records would have some special plant unto themselves, utterly removed from the old-fashioned processes that turned out "shellac" records, guess again. The record pressing machine is truly a versatile instrument. The required adaptation is all made quite simply (though no doubt the original research and experiment were anything but simple) with existing machinery, and thus 33s, 45s, and 78s can be fabricated side-by-side all in the same room. The same goes for the "shellac" and plastic records. Just a matter of a different type of biscuit and a different pressing cycle, different heats, and different timings. The LP pressing process is more carefully managed than the old 78's, being a somewhat slower process per record. In terms of playing time, however, the LP is far faster in the processing than its equivalent shellac forerunner. Six 78 records that's twelve stampers-to one LP with two stampers.



The record pressing department is actually a rather quiet and unobtrusive corner of any large record-making plant. The big noise and the big machinery and the big (and dirty) storage and conveyer space are parts of the pre-pressing operations that end in the biscuit. Record material is, except for the infrequent pure vinylite, a mixture of ingredients. The mixing cannot, unfortunately, be done merely by pouring materials together or dissolving them conveniently in a solvent. Grinding is a major operation here - grinding of recycled material, grinding and mixing of new raw material. Heat, huge furnaces, prodigious rollers squashing out tons of half-melted ooze, great cutter wheels that slice acres of hot ooze into convenient rolls or into the ultimate small biscuits, immense heaps of dusty bags, whole bins of smashed and crushed reject disks, huge hoppers full of black powder, enormous mills that grind tons of coarse material down to fine... these elements of a mighty manufacturing process made up the typical large-scale pre-pressing operation. The modest, hand-operated individual record presses are utterly dwarfed.

Rejected new records and assorted old ones brought in from outside are a major raw material. Ground up whole, labels and all, they were used for the insides of laminated records. But for other use the paper labels must be removed, and since this is impractical, the centers are simply stamped out in a big press, the remaining outside doughnut chopped up and then ground down to feed back into the endless production lines. Little seems to be lost.

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