Which way does the tape go?

[Biggles]

Pardon my ignorance, but it's a very long time since I had anything to do with reel to reel tape machines. Which side of the tape faces into the head, shiny or matt?
Alan.

[Phil G4SPZ]

Matt, though there are a few exceptions. The usual sign that you've got it wrong are muffled sounds, playing in reverse!

[Biggles]

Cheers Phil. Well something in the back of my head was telling me matt, but I have a machine in to look at for a friend and it won't record. All the tapes are wound so that when spooled up they are shiny side to the head. Hence the question. This may explain a lot. Very strange what presents itself on occasion. I actually used to look after Racal ICR64 comms recorders in the eighties. Sometimes they were an absolute to repair. A long time ago and to be honest is probably why I have no interest in them nowadays. No memory at all of which way the tapes went.

Alan.

[Radio Wrangler]

Some posh tape has a deliberate matt coating on the back so that it spools more evenly. Be sure not to use it in any machine which uses pressure pads to apply the tape to the heads. This matt coating is matter than the magnetic coating.

Normal tapes are shiny mylar to the outside and usually a matter finish on the side which goes to the heads.

So back coated tapes go shinier side to the head, tape without back coating go very shiny side away from the head. Racal Zonal were fond of a blue back coating which left you in no doubts..

David

[Phil G4SPZ]

Well Alan, all I can say is that all the consumer-grade and BASF tapes I've ever seen in over 50 years of tinkering with reel-to-reel machines have the matt side towards the heads. The oxide coating sits on one side of the plastic substrate, leaving the 'back' of the tape looking shiny. This also offers lower friction to the felt pressure pads. However, some tape types - of the semi-pro or professional grades - are known to look different and it can be hard to tell which side is which. The easiest way is to replay a known good pre-recorded tape, if you can get hold of one.

EDIT: Post crossed with David's but we are saying much the same thing!

[Biggles]

Ok thanks. The tapes I have just look like the normal matt one side, shiny the other so I'm pretty certain which way they go now. Just one of those daft things I have forgotten over the years!

[Phil G4SPZ]

It will be interesting to hear what happens once you've wound a tape on the reels the right way round, and also to find out how the tapes came to be incorrectly wound in the first place!

[ricard]

The standard since the 50s has been to have tape wound 'oxide in', and the heads are correspondingly mounted (i.e. facing 'outwards'). But early German machines (and I've been told early Tandbergs; possibly many others too) had the heads mounted facing inwards and correspondingly the tape has to be wound 'oxide out'.

In literature of the time the 'oxide in' wind seems to be called the 'International standard' or 'A-wind', with 'oxide out' being called the 'German standard' or 'B-wind'.

I was once given a batch of tapes to transcribe recorded in the mid-50's on some machine with this characteristic; they were all spooled 'oxide out', and had to be twisted half a turn before playing back on any machine that I had. Furthermore, they were two track tapes, and since the head recorded on the top half, which became the bottom half after twisting, I had to play them back using track 3 of a four-track machine as I didn't have a two-track machine which could play back the lower half of the tape.

Then there were confusing machines of that era which had different winds on the two reels, which also meant that the reels turned in opposite directions! The Philips EL3540 is one such machine (see https://www.youtube.com/watch?v=JpN8qfLwU5s for a demonstration) and I believe there were also EMI machines too. (On the EL3540, the supply reel needs to be wound 'oxide out', but rotates 'backwards' and the tape path is conventional with the heads facing outwards; the supply reel is then wound 'oxide in'. Presumably this was done to make the fast wind function simpler to implement in some respect.)

[brenellic2000]

... don't forget the very early 'homologous' tapes which had the magnetic oxide and carrier plastic rolled as one - these were glossy both sides!

[ricard]

I've only ever heard of them, never seen one, I suspect they weren't very popular? Who made them?

[Ted Kendall]

Homogeneous tape was one of the variants used on the original Magnetophon, but didn't translate well to lower speed operation. Geneton survived into the 1950s, and was used by Abbey Road for some time when there were QC issues with EMI H50.

Zonal 675, incidentally, has a mirror finish on the oxide side and a matt back, both black!

[Biggles]

Thanks for all your input. The recorder I am working on which prompted this question still refuses to record even with the tape wound oxide in. Further investigation is required. The bias oscillator is running ok but I suspect that the control logic isn't switching over to record somehow. The tapes are Ampex and it is an eight track studio machine TEAC 80-8 which won't record on any of the eight channels hence the suspicion falling on some common problem like bias or switching. Supplies all check out fine. I have an electronic copy of the service manual but it's proving to be a bit of a stubborn fault to shift.
Alan.

[Herald1360]

Wasn't storage oxide side out favoured at one time?

I had an old EMI deck once where the spools turned in opposite directions- you had to rewind a tape before playing it.

[brenellic2000]

Oxide-in tapes were often wound oxide-out on the take-up spool on professional decks to force full rewind before replay. There were various theories from operational discipline to minimising print through effects in long term storage... but the critical factor there is temperature!

Barry

[julie_m]

There was an urban myth about "oxide-out" storage reducing print-through. But in fact, the signal is just as likely to print through in either direction -- through its own backing tape into the oxide of the layer behind, or through the backing tape of the layer in front into its oxide.

[Ted Kendall]

Michael Gerzon wrote an authoritative article about this in 1972, which you can access through the Audiosignal website. The recommendation is tail-out, oxide-in, which is the way we used to work at Transcription Service.

[ricard]

As I recall, the reason for the tail out storage is that while print through does take place in either direction, it is more noticeable when the echoes come before the original sound, as natural decay of sounds and reverb always come after the main sound, thus masking the print through echo somewhat. Another part of the puzzle is the fact that the print through is not homogeneous; the surface of the magnetic layer that is closest to the source of the print through will be more magnetized than the surface that is farther away. Thus, with tail-out storage, the visible surface of the oxide side of the tape will be more subject to post-echo rather than pre-echo, yielding a less pronounced print through for the previously mentioned reasons.

[TIMTAPE]

Print through was especially bad when we recorded Talking Books to analog tape. It was a perfect storm: unaccompanied speech with silence between words and phrases, and due to the need to accommodate the very long programmes, use of thin long playing tapes. Because the tapes had to be recorded in both directions, tail out storage was no help. Another reason the change to digital recording helped.

[EMI BTR 3]

Originally Posted by Biggles

The tapes are Ampex and it is an eight track <snip>

All the common Ampex (latterly Quantegy after 1995) tapes your 8 track would use (406/407, 456, 499, GP9) have oxide coatings of various shades of dark brown--that's the side that should face the heads.

[jamesperrett]

Originally Posted by Biggles

The tapes are Ampex and it is an eight track studio machine TEAC 80-8

These tapes are likely to be back coated so the brown side should be in contact with the head. The matt black side should be away from the head.

They are also likely to be shedding by now (most Ampex tapes suffer from binder breakdown after a few years) so you will need to clean the heads and guides every minute or so.