The off groove or dead vinyl markings on old Decca LP’s gives a lot of interesting information. By investigating and understanding these number, you can improve your knowledge of the LP. The identification of these numbers and letters can give an indication of the age and version of the LP’s in your collection. The markings are directly related to the manufacturing process.

Here is a short presentation of the manufacturing process in the 60’s at DECCA Record Company. I have had great support in confirming the information on this page as well as the page on Matrix Numbers from non other that Mr L, George Bettyes who kindly contacted me back in 2009:

A big thank you goes to Mr L aka George Bettyes who has kindly given me lots of information.
He worked as a Disc Mastering Engineer at DECCA Studios from 1957 to 1972.

Decca Pressing Plant

George Bettyes: During the time I was working at the Decca Studios there was only one pressing plant. It was located on the outskirts of London at a place called New Malden. The address was:

BURLINGTON ROAD
NEW MALDEN
SURREY

All the masters were cut at the studios at

Broadhurst Gardens
West Hampstead
North West London

Every day they were dispatched to the plant at New Malden for processing and pressing. To my knowledge there was never any other Decca pressing plant in the UK.

Manufacturing

Master tape

Everything starts from the master tape. A master tape is the ready mixed and produced set of songs that should be on one side of the final record. To be able to get the sound from the tape down to a disc we need a Lacquer Disc and a cutting (recording) machine called a Mastering Lathe.

Laquer disc, also called Master disc

This is a thin aluminum plate that has been coated with a thin layer of lacquer. The surface has to be absolutely perfect as any damage whatsoever may have an impact on the final sound on the record.

Laquer Matrix, Master Laquer

Lacquer disc is put into the Mastering Lathe machine. The master tape is plaid and the sound from the tape creates a vibration in the cutting needle that cuts the grooves into the surface of the Lacquer disc. The ready cut disc is then called a Lacquer Matrix. If the disc is approved in quality control, then it will be called Master Lacquer. The matrix number is then added on the approved Master Laquer on the ”dead wax” area, for example XARL-6271-1A.

This disc is playable. It is used by recording engineers to verify the quality of the sound. The disc is also called an acetate when used for sound quality checking. A new disc is cut again for the manufacturing process if the Lacquer Matrix (acetate) has been approved in the sound checking.

George Bettyes:

For a long play record a 14 inch disc was used and for a 7inch 45rpm record a 12inch lacquer disc was used. This is so that the pitch and depth of cut can be set as there would be no room if the lacquer was the same size as the record. The Mastering Engineer would scribe the matrix number and his identity letter on the outer rim of the lacquer, so that the factory could identify the lacquer before processing. Decca always engraved the matrix number on the dead wax area before processing started.

MetalMaster

The Master Lacquer is then sprayed with a thin liquid chloride and silver solution, the thin chloride is a sensitizer that helps the silver stick to the lacquer. The Master Lacquer with the silver coating is then put in a bath of a nickel solution. An electric current is passed through the solution and the nickel particles in the bath are attracted to the surface of the disc. This process will create a rather hard mirror piece of the Master Lacquer.

The Master Lacquer is then removed from the new metal cover. This new piece is called Metal Master. This disc is a negative one

George Bettyes:

Only one Metal Master could be taken from a lacquer master as being very soft it was usually damaged when being separated from the metal master.

Metal mother

The next step is to create a Metal Mother from the Metal Master. This disc is a positive one, meaning that it could be played. The Metal Mother is numbered. This number will be visible at approximately 9 a clock on a Decca vinyl.

George Bettyes:

Several metal mothers were made from the metal master before it deteriated and could not be used anymore.

Stamper

The stamper is then made from the Metal Mother. This is the disc actually used for pressing one piece of a final record. The stamper number was marked in the off groove area at approximately 3 a clock and a letter from the word BUCKINGHAM was used for the numbering system.

George Bettyes:

A number of stampers can be made from each mother, so that for a large selling record several presses could be set up for the production run. When a stamper is made it has to be carefully centered before punching out the center hole to ensure that the finished record turns true on its center. The outside diameter of the stamper is trimmed of excess material to ensure it fits into the press jaws correctly. A stamper could produce about 2000 discs before it had to be replaced.

Vinylrecord

George Bettyes:

To make the finished record two stampers are fitted into the press, one in the upper fixture ,side one and one in the lower fixture, side two. Labels are then placed in the press and a piece of vinyl is then placed between the plates. The press jaws were then closed and were heated to soften the vinyl to allow it to flow. Then the jaws were cooled to harden the disc, the press was then opened and the finished record was removed from the press ready for inserting in the sleeve.