How are vinall records made?

Question:

How are vinall records made?

Best Answer - Chosen by Asker: [edit] Explanation
The normal commercial disc is engraved with two sound bearing concentric spiral grooves, one on each side of the disc, running from the outside edge towards the centre. Since the late 1910s, both sides of the record have been used to carry the grooves. The recording is played back by rotating the disc clockwise at a constant rotational speed with a stylus (needle) placed in the groove, converting the vibrations of the stylus into an electric signal (see magnetic cartridge), and sending this signal through an amplifier to loudspeakers

[edit] Structure of a typical record
The majority of records are pressed on black vinyl. The colouring material used to blacken the transparent PVC plastic mix is carbon black, the generic name for the finely divided carbon particles produced by the incomplete burning of a mineral oil based hydrocarbon. Carbon black increases the strength of the disc and renders it opaque.

Some records are pressed on coloured vinyl or with paper pictures embedded in them ("picture discs"). These discs can become collectors' items in some cases. During the 1980s there was a trend for releasing singles on colour vinyl— sometimes with large inserts that could be used as posters. This trend has been revived recently and has succeeded in keeping 7" singles a viable format.

Vinyl record standards for the United States follow the guidelines of the Recording Industry Association of America (RIAA).[2] The inch dimensions are nominal, not precise diameters. The actual dimension of a 12 inch record is 302 mm (11.89 in), for a 10 inch it is 250 mm (9.84 in), and for a 7 inch it is 175 mm (6.89 in).

Records made in other countries are standardized by different organizations, but are very similar in size. The record diameters are typically 300 mm, 250 mm and 175 mm.

There is an area about 6 mm (0.25??) wide at the outer edge of the disk, called the lead-in where the groove is widely spaced and silent. This section allows the stylus to be dropped at the start of the record groove, without damaging the recorded section of the groove.

Between each track on the recorded section of an LP record, there is usually a short gap of around 1 mm (0.04") where the groove is widely spaced. This space is clearly visible, making it easy to find a particular track.

Towards the label centre, at the end of the groove, there is another wide-pitched section known as the lead-out. At the very end of this section, the groove joins itself to form a complete circle, called the lock groove; when the stylus reaches this point, it circles repeatedly until lifted from the record. Automatic turntables rely on the position or angular velocity of the arm, as it reaches these more widely spaced grooves, to trigger a mechanism that raises the arm and moves it out of the way of the record.

The catalog number and stamper ID is written or stamped in the space between the groove in the lead-out on the master disc, resulting in visible recessed writing on the final version of a record. Sometimes the cutting engineer might add handwritten comments or their signature, if they are particularly pleased with the quality of the cut.

When auto-changing turntables were commonplace, records were typically pressed with a raised (or ridged) outer edge and label area. This would allow records to be stacked onto each other, gripping each other without the delicate grooves coming into contact, thus reducing the risk of damage. Auto changing turntables included a mechanism to support a stack of several records above the turntable itself, dropping them one at a time onto the active turntable to be played in order. Many longer sound recordings, such as complete operas, were interleaved across several 10-inch or 12-inch discs for use with auto-changing mechanisms, so that the first disk of a three-disk recording would carry sides 1 and 6 of the program, while the second disk would carry sides 2 and 5, and the third, sides 3 and 4, allowing sides 1, 2, and 3 to be played automatically, then the whole stack reversed to play sides 4, 5, and 6.