Elena Ortiz, age 13, of Granite City, I11., for her question:
HOW ARE PHONOGRAPH RECORDS MADE?
The world's first practical phonograph was invented in 1877 by Thomas Edison. His machine used a small metal cylinder that was wrapped in tinfoil and was mounted on an axle that could be rotated. Next to the cylinder was a mouthpiece that included a vibrating disk. A needle was attached to the vibrating disk which recorded sound waves in the foil.
Today's phonograph records are made with the help of a tremendous amount of sophisticated electronics equipment.
It usually starts in a recording studio. On hand are some musicians, a record producer and a recording engineer. The producer decides how the recording should sound, and he can ask the musicians to repeat parts of the music if he feels they didn't come out right the first time. The engineer makes a master tape of the recording session.
Next the master tape must be edited. All mistakes can be removed and just the passages that sound exactly right will be included in the final version.
On schedule next is the transferring of the recording to a disk. A cutting lathe handles this important job. Looking somewhat like a large phonograph, the cutting machine is connected to the tape recorder on which is the edited tape. Attached to the lathe's arm is an electromagnet with a cutting needle set between its poles. A wire coil is built into each side of the magnet. The electric waves magnetize the coil, and the magnetic changes make the needle vibrate.
A blank record, called a lacquer, is put on the turntable. The lacquer is made of plastic coated aluminum. As the lacquer revolves, the cutting needle is placed at the outside edge and begins to cut a V shaped groove. In cutting a stereo lacquer, the needle moves both up and down as well as from side to side.
Phonograph records you buy in a music store are made from the lacquer. If many thousands of copies are to be produced, a number of lacquers are made from the master tape.
Next, metal molds are made by electroplating the lacquer. These are called masters. Then copies called stampers (about 50 can be made from one lacquer) are made of hard nickel. Two stampers, one for each side of the record, press the records you buy.
A piece of plastic called a biscuit goes between two stampers and tremendous pressure is applied. Hot water pipes in the press melt the biscuit which then is imprinted with the record grooves from both stampers.
The entire process of making a record takes about one minute. Each stamper can produce about 500 records. The job is done after the records receive careful inspection and packing.