5.4.3 Cleaning and Carrier Restoration Tape Cleaning: Dirty or contaminated tapes should be cleaned of dust and debris with a soft brush and low vacuum before spooling. Deformed reels may seriously damage tapes, especially in the fast winding mode, and must be replaced before any further steps are carried out. The tape should be carefully spooled guiding the tape so as not to cause damage. The tape may then, if necessary, be spooled on a tape-cleaning machine that has a soft cloth or other lint free material cleaning surface. This may also be beneficial after treatment for hydrolysis (see below). Some tape cleaning or restoration machines pass the tape across a sharp surface or blade, which removed the top layer of oxide. Such machines were developed for the re-use of recorded tapes and are not recommended for archival tapes. Special attention should be paid to dirty cassette tapes as some reputable double capstan machines may damage dirty tapes during replay.Without adequate tape tension control a loop may develop between the capstans. Leader Tapes and Tape Splices: Many tapes have splices either through editing or the addition leader tapes. Such splices are likely to have failed, either through dry failure of the adhesive, or bleeding of the adhesive layer. The former must be replaced. Bleeding splices constitute a more serious problem. The adhesive may spread from the splice to the adjacent layers which may have encouraged the dissolution of the binder. It may also cause the layers to adhere to each other and increase speed fluctuations. Old adhesive must be removed using a solvent that does not damage the binder. Highly purified light fuel is an appropriate solvent and may be applied using a Q-tip or lint free cloth. It is advisable to keep the amount applied to the tape to the minimum required, and no more than would be applied with a Q-tip. As with all solvents, a small amount should be tested on an unused portion of the tape. The tape should be left unwound for a few minutes to ensure full evaporation. Evaporation may be accelerated by an air stream. It is sometimes necessary to replace or add leader tape to enable the complete recording on the tape to be played. Hydrolysis (Sticky Shed Syndrome): When replayed, many of the tapes manufactured since the 1970s show the artefacts of a chemical breakdown of the binder. Often described as sticky shed syndrome, the main component of the reaction is hydrolysis1 , by which term it is often described. It is typified by a sticky brown or milky deposit on tape heads and fixed guides, often accompanied by an audible squeal and reduction in audio quality. The following treatments represent various approaches to the treatment of binder degradation: Room Temperature, Low Humidity: Hydrolysis involves the splitting of a chemical bond through the introduction of water, and providing that an irreversible recombination has not subsequently occurred, hydrolytic reactions should be reversible through the simple process of removing all water. This can be achieved by placing the tapes in a chamber approaching 0% relative humidity (RH) for extended periods of time, up to several weeks. Slightly elevating the temperature increases the reaction time. Tests have shown that this treatment, while successful in some cases does not always completely reverse all the artefacts of a degraded tape (Bradley 1995). Heated Respooling: Sometimes very degraded tapes may bind one layer upon another and uncontrolled spooling may cause damage. In such cases, if baking is not being undertaken, it may be possible to apply warm dry air directly to the point in the tape pack where the tape is sticking, and then commence to unspool the tape at a controlled rate of 10-50 mm per minute. Elevated Temperature, Low Humidity: An approach commonly used in the treatment of hydrolysed tapes is heating the tape in a chamber at a stable temperature approaching 50 ºC and 0% RH for period of around 8- 12 hours. The temperature of 50 ºC probably equals or exceeds the glass transition temperature2 of the tape binder, however, whether that has a long term effect on the physical characteristics of the tape when returned to room temperature is unclear. It does, however, have a positive short term electro-acoustic effect by returning the replay characteristics to original condition. Interleaving with new tape may be of benefit in reducing the level of print activity, which can be activated by temperature increases. Tapes should be rewound a number of times to reduce the effects of print through caused by elevated temperatures (see This latter procedure has a high success rate, but should not be carried out in a domestic oven. Domestic ovens have poor temperature control, which may exceed safe thresholds. Additionally the thermostat control of such ovens cycles back and forward across of range of temperatures and this action may damage the tape. A microwave oven should never be used as it heats small parts of the tape to very high temperature and may damage the tape and its magnetic characteristics. A laboratory oven is preferred, or other stable low temperature device. Higher temperatures should never be allowed as these may cause deformation of the tape. Exposing tapes to controlled, elevated temperatures as described above should be undertaken very carefully and only where absolutely necessary. Restoration may be only temporary, yet should enable replay for transfer. Anecdotal evidence is that hydrolysed tapes which require longer treatment are becoming more prevalent.

1. Hydrolysis: A chemical decomposition by addition of water, or a chemical reaction in which water reacts with a compound to produce other compounds

 2. Glass Transition Temperature;That temperature at which an adhesive loses its flexibility and becomes hard, inflexible, and “glasslike.”