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Vinyl manufacturing
This is a brief overview of vinyl manufacturing, of those parts of the processes which are essential in determining the place of manufacture of a record. It briefly discuss the various steps, and focuses on how matrix codes are applied. For more details about the process itself, I suggest you read the document at The Record Collectors Guild.  Mastering: Lacquer The recorded music is transfered from the tape to a lacquer-coated aluminum disc by a lathe, a tool which spins a block of material to perform various operations. In this case it's cutting the record, the opposite to playing a vinyl, you feed audio in and get mechanical motion out. The audio is cut to the lacquer with a corundum (sapphire) or diamond cutting stylus, and the master is done. It is never played, as that would degrade it. There are several names for it, master, soft master, lacquer, acetate. I stick with lacquer, as it's the substance the music is actually cut to. Lacquer is similar to wax. It is refridgerated if it isn't going to be processed right away, as heats damages it. The mastering/ cutting is often done at other locations by other companies than the making of the metal plates and actual pressing of the vinyl. (Read more: Mastering-only facilities.) Image 1 shows a Nevermind lacquer cut by the Spanish pressing plant Iberofon.  Processing: First negatives (fathers, matrices), mothers, stampers The lacquers are put in a bath and electroplated (mostly with a nickel alloy), and the first pair of metal negatives are made. They are parted from the lacquers with a blow of a special hammer. The lacquers are most often destroyed in this process. The negative metal plates can be used to press vinyl, but only if it's a small pressing, as they would be worn out after about 1000-1200 records, and the cut would be lost. Though if they are in a hurry, several lacquers can be cut and sent to the pressing plant(s) to produce several sets of fathers simulaneously, which they will use for pressing. Often the fathers are plated through another plating process, which forms a set of mothers. Mothers can actually be played for testing, but obviously, you need a negative for pressing. New negative metal plates, stampers, are made from the mothers. Each pair of stampers can press about 1000 records before they start to deform or break. If the record is to be pressed in several countries/ by several plants, more mothers duplicated from the original negatives (fathers), or stampers duplicated from the mothers, can be sent to these plants. However, there is a limit on how many times a father and mother can be plated, which is about six times each. This means one can make a maximum of 36 sets of stampers from a set of lacquers. Often several sets of lacquers are cut instead, as explained above, and sent to the various pressing plants, or to one pressing plant for quicker processing. Plating may take a few hours to a few weeks, depending on the quality of the plates. Images 5, 6, and 7 show a set of stampers used to press the MFSL edition of Nevermind (MFSL 1-258). They came in a plain yellow paper sleeve for each plate. The sleeve for the side A plate has "MFSL-1-258-A2 MFSL S #16873" written on it, and the side B folder has "MFSL-1-258-B2 MFSL S #16789" written on it. "DTD Overnite" is written on both. The plates themselves have, of course, the matrix codes, and "No Oils" is etched in the clamping area (where the vinyl label would go). Image 8 shows a detail from one of the sleeves for the Kill Rock Stars compilation (KRS-201). Pressing dates and quantities are written, along with "B-CRACKED/EDGE NEW SET ON ORDER 1/98". Clearly, it didn't last more than 1000 records. More pictures at sliver.it.  Alternative: Direct metal mastering It is, however, possible to eliminate the two first processing steps by cutting a mother directly in copper plates, called direct metal mastering. An "infinite" number of stampers can be processed from the copper master/ mother. DMM mastering produces records with lower distortion, superior high frequency response, longer program times and quieter surfaces than mastering on lacquers, but as the grooves are shallower, the recording may not be as loud as if it had been cut on lacquer. Dance music, which is often dominated by low frequencies, may skip easily.  Pressing The stampers are mounted similarly to a waffle iron. First a label is placed, then a "biscuit" of vinylite, then the other label, and the top is lowered. The plates are heated with steam to 300 degrees allowing the vinylite to flow into every groove, and quickly cooled with liquid water, and a record is made. Pressing takes about 8-9 hours for 1000 records. Picture discs consist of three layers of vinyl, with the images put inbetween (image 4). The outer layers are obviously clear vinyl, while the color of the vinyl inbetween the pictures may show at the rim of the record. Still, test pressings are usually made as regular black vinyl. A few videos on Youtube.com show the process from mastering to finished records. Note that they omitt some of the processing, and just use the first metal plates as stampers:  How vinyl records are made part 1/2  How vinyl records are made part 2/2  Mixed colors Mixed or impure colors happen from time to time. Sometimes the same stampers are used to press two different colors. Instead of cleaning the stampers between pressing the two colors, they just feed the new colors directly, so the few following records will have remains of the first color. This was done when Erika pressed the Molly's Lips single (images 9-10). These copies were still sold. If the hopper which feeds the melted vinyl grains to the machines isn't cleaned properly after pressing a given color, the new pressing on a different color may contain small traces of the old color. Also, sometimes recycled vinyl isn't completely clean, this will also contain impurities of different colors.  Matrix codes Text may be added to the matrix code at three times; by the mastering facility, by the processor, and by the pressing plant, unless some or all these companies are the same. In most cases, the record is mastered by a different company than the pressing plant. It is possible to see in which stage a part of the matrix was added without knowing much about either companies. The code left by the mastering facility will be added to the lacquer with a stylus, so it appears deep and smooth. They usually write the catalog number and side A/B information, sometimes the name of their company, the signature of the mastering engineer, which plants will receive the lacquers, and maybe funny remarks. If a lacquer turns out to be faulty, they'll have to recut the record. They show this by writing RE1, RE2, etc in the matrix code, which means remake 1 etc. The processor then may add their archive numbering system or pressing plant signature to either the lacquers or to the mother plates once they've made them. (Obviously, the only metal plates one can add to the matrix code to, is to the mother plates, as the fathers and stampers are negatives.) The lacquers are very fragile, so it is often done to the metal plates. Etching into metal is obviously harder, so these additions will be more faint and less smooth than the mastering matrix. Even if the processor etches their additions into the lacquers, it can be told apart from the mastering matrix as they are often less smooth. For example, if they have to redo the mothers, they may etch RE1, but this can easily be told apart from a "master RE1". If yet another company is pressing the records, they will often receive a set of mother plates to make the required number of stampers. The pressing plant will then maybe add their archive numbering system to the mother plates, so we can get etchings from three companies. Examples of this can be seen on the Oh, The Guilt 7" singles. Another example is the Bleach plates which Orlake received from MPO. They scratched out MPO, but didn't bother to write their own name. It is slightly different when using DMM mastering. The matrix can only be written on and added to on the mothers. Still, the mastering facility and processor/ pressing plant may not be the same company, or simply different divisions of the same company, so the different parts of the matrix may be etched at different times and by different people. Unfortunately these etchings may be equally deep and "smooth", only differ slighly from person to person. DMM matrix codes are usually deeper than those additions done to the metal plates made when using the lacquer technology.  Recycling and quality Most records are made from recycled vinyl. The label area is stamped out, and the rest of the records are ground to powder and eventually made into the above-mentioned biscuits. Impurities may cause audio artifacts like clicks and pops. Some records are made from virgin vinyl, like the Simply Vinyl pressings of Nevermind, In Utero, and Unplugged in New York, and they are also often heavier, 180 - 220 g/m². They have been reported to have better sound quality, and they withstand wear from normal play better then regular vinyl. The vinylite is a mix of several materials which improves the quality. One is ultra-fine carbon, which makes the vinyl look black. As colored vinyl miss the black carbon, they are of lower quality than opaque black vinyl.
1. Nevermind lacquer cut by Iberofon 2. Neumann DMM cutting head 3. DMM copper plate being cut, and finished mother 4. Close-ups of the Czech Nevermind picture disc, showing the blue vinyl inbetween 5. Side A pressing plate for MFSL Nevermind 6. Side B pressing plate for MFSL Nevermind 7. Side B matrix on MFSL Nevermind stamper 8. Sleeve detail for Kill Rock Stars stampers 9. Molly's Lips with mixed colors, traces of black 10. Molly's Lips with mixed colors, almost entirely black Thanks to The Record Collectors Guild, EIL, Wikipedia, The Sound-O-Mat Studio, Recordpressing.com, Aaron Baker, Remix Magazine, Elysia (images 2-3), Enrico Vincenzi (images 1, 4, 8), Jeremy Little (images 5-6), Guido Maria Muscelli (image 9), and Dave (image 10).

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