Vinyl Record

Oxide Shedding

There are essentially three weak links in any tape system – the magnetic layer, the binder and the substrate.  Problems with deterioration of the substrate layer, apart from the inevitable `cupping’ and `brittle backing’ of acetate tape are rare.  However problems with the binders are leading to `sticky tape syndrome’ and `squealing’.

Some brands and batches of reel-to-reel tape are prone to sticky tape syndrome.  This occurs when the tape’s oxide layer becomes `sticky’ and adheres to the machine heads etc. during playback, rendering some recordings unplayable without manual cleaning or baking.  (See separate chapter).

The typical binders used in tapes are polyester-polyurethane based and are subject to hydrolysis in humid environments.  This causes the breaking down of the cross-linked binder which renders the binder gummy.  This `gummy’ substance can then migrate to the surface of the tape causing resulting in the debris which causes head clogs and dropouts.  This `syndrome’ is characterised by high tape friction and low coating integrity.  The high friction can result in tape seizing and the general inability of tape to be transported in the drive.  The lower coating integrity can result in debris which causes head clogs and dropouts.

`Squealing’ can often be caused by a build-up of debris in the guides or heads.  A more serious problem is due to the tape having poor lubrication, or losing its lubrication through age.  This problem is not easy to eliminate.  It is possible to re-coat the tape with a lubricant solution in order for a copy to be made.  A more practical solution is often to reduce the tape-to-head tension or remove all stationary surfaces from the tape path.

Some of the earlier recordings made by NWSA on unbranded stock are also showing signs of deterioration.  However it is unclear at this stage whether this is due to sticky tape syndrome or some other form of oxide shedding such as general `rub-off’ of the oxide layer.

Urgent conservation work needs to be undertaken to transfer affected stock to more permanent carriers before some important collections are lost forever.

Acetate tape showing signs of cupping

Paper tape showing creasing and oxide shedding

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