All About Recording Tapes

October 7, 2016

Now a day’s its very easy to record, preserve and replay any sound of music just with a touch of a button. In the earlier days it was not this simple. Walking through the era where tapes evolved, in the 1890’s Valdemar Poulsen first developed a magnetic sound recording tape. The materials he used in the manufacturing were a solid band of magnetically hard steel; this tape had a life span of about 40 years, until the 1930’s.However there was a different approach which suggested the use of non-magnetizable powder coated carriers like paper or plastic, made out of magnetizable materials. The 1930’s saw use of these materials and a German company called I.G Farben, improvised such tapes with AEG Magnetophon.

World War II saw a transformation, as an effect I.G Farben process was transferred to England and the United States of America in order to make further improvisations. Pictures in this article show a few major operations which were imperative in the making of Recording tapes, representing the state of art around 1955.
A special form of Iron Oxide called Gamma-ferrous oxide is used in the finest form; first the elongated particles are put in balls and mixed with binders, plasticizers and other materials. The large container on the top of the image is the ball mill, inset is huge steel balls used to pulverize and mix the ingredients.

Liquid mixture is stored in tanks before being delivered to the coater.

The Tape coater is a piece of equipment which is very similar to the ones used in printing while applying special coatings to paper, it also spreads a thin layer of oxide mixture to an acetate or Mylar plastic which is about three feet wide. The wet tape is then forced to a strong magnetic field, in order to arrange long and thin oxide particles. The tape is also dried with extra efforts and sometimes even polished on the coating line. Post which the final product, the recording tape can be seen coming out of the machine.

Few of the manufacturers ran the finished tape through a slitter immediately; while others stored the unslit tape. Mid- 1950s saw the best tape coming from near the center of the width. Computer and video tapes were a piece taken from the center, whereas audio tapes were taken from near the edges. The lowest quality tape, from the extreme edges was sold as “budget” audio tape.

This is how tapes evolved and good music was recorded and stored.