RTM & The 21st Century Tape Revival

An 80cm‑wide roll of freshly made tape is cut into quarter‑inch strips at the RTM factory.

We track the analogue renaissance back to its source: Europe’s last remaining factory manufacturing magnetic tape.

In his SOS December 2024 leader, Sam Inglis declared: Tape Is Back! Actually, like vinyl records, analogue tape never really disappeared. Manufacturing and sales continued, even as digital and then hard‑disk recording ruled among audio professionals.

The magnetic recording industry was once huge: there were more than 20 manufacturers in the US, including 3M and Ampex, and 12 in Europe, with BASF, Agfa, EMI, MSS, Zonal and Pyral among the largest. Japan, too, had Maxell and TDK. Today, there’s only one analogue tape factory left in Europe: RTM Industries, aka Recording The Masters, located in Avranches, Normandy, France. Their catalogue includes professional and consumer audio tape in various formats and lengths, and even cassettes!

A Brief History Of Tape

German engineers developed magnetic recording in the 1920s. The original medium was steel wire or steel tape; fidelity was poor, but it allowed longer recordings than discs of the era. Tape as we know it was invented in the 1930s by BASF for the Magnetophon that AEG had just developed. German engineer Fritz Pfleumer had patented a process for putting iron oxide powder on cigarette paper, using a lacquer as binder. BASF replaced the paper with cellulose acetate, improved the iron powder and the binder, and supplied AEG with magnetic tape for the Magnetophon in 1934. The new machine created a sensation at the Berlin International Radio Fair in 1935; the audio quality was pretty good, and it was used intensively by radio stations, contributing to Hitler’s propaganda all around Germany. Tape quality got better, and the next major step forward was the introduction of AC bias by AEG in 1943, delivering 60dB dynamic range and a frequency response of 50Hz to 10kHz. Tape could be cut with scissors and edited at will, easily copied, erased, shipped, and allowed long recording times (up to 22 minutes).

Before the outbreak of the Second World War, AEG demonstrated an early Magnetophon tape recorder to US electronics giants General Electric in hopes of securing a licence agreement. GE failed to recognise the potential of the early Magnetophon, putting their faith in wire recording instead. The Magnetophon was rediscovered by an American officer in Frankfurt at the end of WWII, brought to the US and further developed by manufacturers Ampex. Chemicals specialists 3M supplied tape using PVC as a base film, with better oxide. In 1948, Bing Crosby, who had funded Ampex, recorded his syndicated radio shows on tape with Ampex Model 200 machines, giving the new system a major application. Analogue tape recording then spread worldwide and revolutionised the entertainment and information industry. In the United Kingdom, EMI unveiled the Magnetophon‑based BTR1 in November 1947.

In a two‑track, quarter‑inch master tape rolling at 15 inches per second, the playing head encounters 80 million magnetic particles per track per second.

How It’s Made

Today, magnetic tape is still made of a thin plastic base film, bonded with ferric oxide on one side and an antistatic coating on the other side. On RTM SM911 ‘pro’ tape, the base film is 30µm thick, the magnetic layer itself 16µm, and the back coating 2µm. On RTM LPR90 ‘consumer’ tape, the relative thicknesses are 20, 11.5 and 4.5 µm. Every physical aspect is important: base film must not be too rigid or elastic to cope with mechanical pressures such as acceleration and braking during fast‑forward/rewind. Back coating is key to a regular winding, with or without flange. The thickness of the oxide coating determines the maximum output level, the number of magnetic particles it contains affects treble response, and its regularity ensures the absence of dropouts. In a two‑track, quarter‑inch master tape rolling at 15 inches per second, the playing head encounters 80 million magnetic particles per track per second.

These bottles contain samples of all the ingredients needed to produce magnetic tape: ferric oxide, resins, solvents and more.Ferric oxide and coating are laid down on the plastic carrier by a specific coating machine. The one used by RTM is one of the last ever made, the E9, purchased from the RMG International plant in Oosterhout, Netherlands in 2012. It handles huge rolls: 6km long and 80cm wide, they weigh 200kg each. The emulsion is drained from the vessels where it was made and carefully filtered before hardening agents are added. It is pushed through the casting head at a precisely defined pressure. The base PVC film is cleaned and ionised for better adherence before it reaches the casting head. The final magnetic coating thickness must be consistent to ±0.5% across the whole width and length of a roll, as well as between rolls. Oxide coating is prepared from different ingredients — granulates of ferric oxide and resins, solvent, binder, and more — most coming from China. These are carefully controlled before use, then mixed in 5000‑litre storage tanks according to precise recipes that determine viscosity, temperature, grinding fineness and so on. From these raw materials, two types of emulsion are prepared: magnetic slurry and back‑coating solution. Pellets and pigments are mashed by ceramic spheres, and seamlessly mixed, to break agglomerates without brutalising magnetic materials (otherwise tape coercivity would suffer).

Magnetic slurry is obtained by dispersing the magnetic...