treatment

13
Sep
2019

Mouldy Tape

The effects of mould growth on both the integrity of the tape and the recorded sound or image can be significant.

Mould growth often sticks the tape layers in a tightly packed reel together often at one edge. If an affected tape is wound or played this can rip the tape.

In the case of narrow and thin tapes like DAT, this can be catastrophic.

opened up DAT cassette shell with white powdery mould on upper surface of tape wound around red plastic spool

DAT audio cassette shell opened to reveal visible mould on edge of tape pack

DVCPRO video cassette lid lifted to show tape split longitudinally

If the mould has damaged the record side of the tape then the magnetic tracks are usually damaged and signal loss will result. This will create audible and visual artefacts that cannot be resolved.

Mould develops on tapes that have been stored in less-than-optimum conditions. Institutional collections can exhibit mould growth if they have not have been stored in a suitable, temperature controlled environment. For magnetic tape collections this is recommended at 15 +/- 3° C and 40% maximum relative humidity, although the British Library's Preservation Advisory Centre suggest 'the necessary conditions for [mould] germination are generally: temperatures of 10-35ºC with optima of 20ºC and above [and] relative humidities greater than 70%.'

For domestic and personal collections the mouldy tapes we receive are often the ones that have been stored in the shed, loft or basement, so be sure to check the condition of anything you think may be at risk.

We do come across cases where mould is not easily visble to the naked eye without dismantling a cassette shell - so unless you can be sure your tape has been kept in optimum storage conditions for its entire 'life', it's better to err on the side of caution. Playing a mould-affected tape in a domestic machine can very easily damage the tape.

It is important to remember that a mouldy tape is a hazard not just for the individual tape. If not handled carefully it can potentially spread to other parts of your collection, so must be treated immediately.

filaments of mould on Hi8 video tape edge

Hi8 tape showing longitudinal tear caused by sticking

What can we do to help?

We have a lot of experience treating tapes suffering from mould infestation and getting great results!

There are several stages to our treatment of your mouldy tape.

Firstly, if the mould is still active it has to be driven into dormancy. You will be able to tell if there is active mould on your tape because it will be moist, smudging slightly if it is touched. If the tape is in this condition there is a high risk it will infect other parts of your collection. We strongly advise you to quarantine the tape (and of course wash your hands because active mould is nasty stuff).

When we receive mouldy tape we place it in a sealed bag filled with desiccating silica gel. The silica gel helps to absorb the tape's moisture and de-fertilises the mould's 'living environment'.

When the mould becomes dormant it will appear white and dusty, and is relatively easy to treat at this stage. We use brushes, vacuums with HEPA filters and cleaning solutions such as hydrogen peroxide to clean the tape.

Treatment should be conducted in a controlled environment using the appropriate health protections such as masks and gloves because mould can be very damaging for health.

All machines used to playback mouldy tape are cleaned thoroughly after use - even tapes with dormant mould still carry the risk of infection.

Most tapes-infested with mould are treatable and can be effectively played back following the appropriate treatment procedures. Occasionally mould growth is so extensive however that it damages the binder irreparably. Mould can also exacerbate other problems associated with impaired tape, such as binder hydrolysis.

gently dislodging mould from U-matic video tape

Edge and upper-surface mould causing U-matic video tape to stick

When it comes to tape mould the message is simple: it is a serious problem which poses a significant risk to the integrity of your collection.

If you do find mould on your tapes all is not lost. With careful, specialised treatment the material can be recovered. Action does need to be taken promptly however in order to salvage the tape and prevent the spread of further infection.

Feel free to contact us if you want to talk about your audio or video tapes that may need treatment or assessment.

Posted by greatbear in audio tape, video tape, 8 comments
17
Oct
2016

Spoking – Treating and Assessing Magnetic Tape

Assessment and treatment is an important part of Greatbear’s audiovisual preservation work. Even before a tape is played back we need to ensure it is in optimum condition. Sometimes it is possible to make a diagnosis through visual assessment alone. A tape we received recently, for example, clearly displayed signs of ‘spoking.’

Spoking is a term used in the AV preservation world to describe the deformation of the tape pack due to improper winding, storage or a badly set up machine. The National Archives describe it as a ‘condition of magnetic tape and motion picture film where excessive pressure caused by shrinkage or too much winding tension eventually causes deformation.’

In our experience ‘spoking’ predominantly occurs with domestic open reel tapes. We have rarely seen problems of this nature with recordings made in professional settings. Compared with professional grade tape, domestic open reel tape was often thinner, making it cheaper to produce and buy.

‘Spoking’ in domestic tape recordings can also be explained by the significant differences in how tape was used in professional and domestic environments.

Domestic tape use was more likely to have an ‘amateur’ flavour. This does not mean that your average consumer did not know what they were doing. Nor were they careless with the media they bought and made. It cannot be denied, however, that your average domestic tape machine would never match the wind-quality of their professional counterparts.

In contrast, the only concern of recording professionals was to make a quality recording using the best tape and equipment. Furthermore, recording practices would be done in a conscientious and standardised manner, according to best industry practice.

Combined, these factors result in a greater number of domestic tapes with winding errors such as cinching, pack-slip and windowing.

Treating Spoking

The majority of ‘spoking’ cases we have seen are in acetate-backed tape which tends to become inflexible – a bit like an extended tape measure – as it ages. The good news is that it is relatively easy to treat tapes suffering from ‘spoking’ through careful – and slow – re-winding.

Slowly winding the tape at a controlled tension, colloquially known as ‘library wind’, helps relieve stress present in the pack. The end result is often a flatter and even wound tape pack, suitable for making a preservation transfer.

Posted by debra in audio tape, 0 comments
31
Mar
2014

Climate Change, Tape Mould and Digital Preservation

The summer of 2008 saw a spate of articles in the media focusing on a new threat to magnetic tapes.

The reason: the warm, wet weather was reported as a watershed moment in magnetic tape degradation, with climate change responsible for the march of mould consuming archival memories, from personal to institutional collections.

The connection between climate change and tape mould is not one made frequently by commentators, even in the digital preservation world, so what are the links? It is certainly true that increased heat and moisture are prime conditions for the germination of the mould spores that populate the air we breathe. These spores, the British Library tell us

‘can stay dormant for long periods of time, but when the conditions are right they will germinate. The necessary conditions for germination are generally:

• temperatures of 10-35ºC with optima of 20ºC and above

• relative humidities greater than 70%’

The biggest threat to the integrity of magnetic tape is fluctuations in environmental temperatures. This means that tape collections that are not stored in controlled settings, such as a loft, cupboard, shed or basement, are probably most at risk.

While climate change has not always been taking as seriously as it should be by governments and media commentators, the release today of the UN’s report, which stated in no uncertain terms that climate change is ‘severe, pervasive and irreversible’, should be a wake up call to all the disbelievers.

To explore the links between climate change and tape degradation further we asked Peter Specs from US-based disaster recovery specialists the Specs Brothers if he had noticed any increase in the number of mouldy tapes they had received for restoration. In his very generous reply he told us:

‘The volume of mouldy tapes treated seems about the same as before from areas that have not experienced disasters but has significantly increased from disaster areas. The reason for the increase in mould infected tapes from disaster areas seems to be three-fold. First, many areas have recently been experiencing severe weather that is not usual for the area and are not prepared to deal with the consequences. Second, a number of recent disasters have affected large areas and this delays remedial action. Third, after a number of disasters, monies for recovery seem to have been significantly delayed. We do a large amount of disaster recovery work and, when we get the tapes in for processing fairly quickly, are generally able to restore tapes from floods before mould can develop. In recent times, however, we are getting more and more mouldy tapes in because individuals delayed having them treated before mould could develop. Some were unaware that lower levels of their buildings had suffered water damage. In other areas the damage was so severe that the necessities of life totally eclipsed any consideration of trying to recover “non-essential” items such as tape recordings. Finally, in many instances, money for recovery was unavailable and individuals/companies were unwilling to commit to recovery costs without knowing if or when the government or insurance money would arrive.’

Nigel Bewley, soon to be retired senior sound engineer at the British Library, also told us there had been no significant increase in the number of mouldy tapes they had received for treatment. Yet reading between the lines here, and thinking about what Pete Specs told us, in an age of austerity and increased natural disasters, restoring tape collections may slip down the priority list of what needs to be saved for many people and institutions.

Mould: Prevention Trumps the Cure

Climate change aside, what can be done to prevent your tape collections from becoming mouldy? Keeping the tapes stored in a temperature controlled environment is very important – ’15 + 3° C and 40% maximum relative humidity (RH) are safe practical storage conditions,’ recommend the National Technology Alliance. It is also crucial that storage environments retain a stable temperature, because significant changes in the storage climate risk heating or cooling the tape pack, making the tension in the tape pack increase or decrease which is not good for the tape.

Because mould spores settle in very still air, it is vital to ensure a constant flow of air and prevent moist conditions. If all this is too late and your tape collections are already mouldy, all is not lost – even the most infected tape can be treated carefully and salvaged and we can help you do this.

If you are wondering how mould attacks magnetic tape, it is attracted to the binder or adhesive that attaches the layers of the tape together. If you can see the mould on the tape edges it usually means the mould has infected the whole tape.

Optical media can also be affected by mould. Miriam B. Kahn writes in Disaster Response and Planning for Libraries

‘Optical discs are susceptible to water, mould and mildew. If the polycarbonate surface is damaged or not sealed appropriately, moisture can become trapped and begin to corrode the metal encoding surface. If moisture or mould is invasive enough, it will make the disc unreadable’ (85).

Prevention, it seems, is better than having to find the cure.  So turn on the lights, keep the air flowing and make the RH level stable.

Posted by debra in audio tape, video tape, 0 comments