tape repair

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

video tape split diagonally, with no visible signs of mould on surface of tape

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.

fine filaments of white and golden brown mould on edge of tape wound around white plastic spool

filaments of mould on Hi8 video tape edge

diagonal tear across 8mm tape on spool

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.

white powdery mould with cleaning cloth inside U-matic tape sheel

gently dislodging mould from U-matic video tape

fine line of white mould on edge and upper surface of black 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, 4 comments
Type IV Metal Cassettes and Robert Chenciner’s Daghestan Collection

Type IV Metal Cassettes and Robert Chenciner’s Daghestan Collection

We recently received a fascinating collection of tapes from the archive of Robert Chenciner, an ethnographer with over thirty years experience studying the cultures, human rights and current affairs of Daghestan.

Daghestan is located in the north Caucasus region, its neighbouring countries are Azerbaijan, Chechnya and Georgia, while its eastern border is flanked by the Caspian Sea.

In the early 1980s Robert had unique access to Daghestan and other parts of the Soviet Caucasus in the twilight years of the USSR.

During visits Robert made recordings of Daghestan’s rich culture. This included music, documenting ethnic instruments such as the Chagana, as well as singing and dancing.

Although Robert believes that claims to authenticity must be treated with suspicion, he nonetheless told me that these recordings document the traditional folk culture that was practiced in the villages of Daghestan.

These tapes also document the 31 mutually unintelligible languages spoken in Daghestan such as Avar which is spoken by 900,000 people.

Listen to excerpt of a tape from the collection. The tape had experienced mould growth and had snapped. It therefore needed to be repaired prior to transfer. Robert explains: ‘The recording was made in Untsukul c.March 1990. You can hear Russian being spoken with a heavy accent, some Kumyk and some Avar. It was joking and talk about who was I and where from.’

Type IV metal cassette with shell open. Visible thin layer of dust on the surface.

Type IV Metal Cassettes

When Robert travelled to Daghestan he was keen to get the most professional recordings he could. For this reason he used type IV metal audio cassette tapes, a tape formula that had been introduced in the late 1970s to offer better quality recordings.

By the mid 1980s, the tape tardis explains, these tapes

‘had been adopted by a lot of enthusiasts. They remained too expensive to be bought in bulk by the average consumer, but if you wanted to record something special – and particularly if you produced music yourself – you’d probably be highly attracted by the exceptional recording quality of a good metal cassette.’

The science behind the type IV cassette, according to the Museum of Obsolete Media, was to use ‘pure metal particles instead of metal oxides. This created a hard-wearing tape with superior frequency response and greater dynamic range.’

Since completing the recordings in the mid 1980s, as with so many of the tapes we receive at Greatbear, they have been tucked away in a drawer and out of circulation.

Due to being stored in poor conditions some of the tapes were displaying signs of mould growth.

Another problem some tapes exhibited was the degradation of the foam pressure pad. This had ‘stuck’ onto the tape and stopped it it from playing. In one case the tape had snapped as a result from a previous attempt at playback. Melted foam pressure pad on a type IV metal tape

Fortunately this issue did not effect our ability to do the transfer. We use Nakamichi tape decks to do optimal audio cassette transfers. The transport design within Nakamichi machines doesn’t use the tape pressure pad to play back the tapes. This is because, Wikipedia tells us,

‘Nakamichi found that this pad provided uneven and fairly inaccurate pressure and was therefore inadequate for reliable tape/head contact. Furthermore, Nakamichi found that the pressure pad was a source of audible noise, particularly scrape flutter (the tape bouncing across the head, a result of uneven pressure), and also contributed to premature head wear. Nakamichi’s dual-capstan tape decks provide such accurate and precise tape tension that, unlike other decks, the cassette’s pressure pad is not needed at all.’

Head pad lifter on a Nakamichi tape machine

The insides of a Nakamichi machine that has no need of a pressure pad to play back tapes.

Re-publication plans

Recent interest from musicologist Stefan Williamson-Fa, the driving force behind getting the tapes transferred to digital files with Great Bear, will enable these unique recordings to be heard by new audiences.

These include what Robert believes to be the only recording of an Andi Zikr ritual. Banned by the Tsar and later the Soviets, the Zikr ritual proved to be a resilient part of Daghestan’s Sufi culture. Zikr involves a group rotating in a circle, stamping the ground and grunting in order to create a mystical and ecstatic experience.

Stefan and Robert have plans to make the transferred digital files available online.

Robert reflected that when he was collecting the tapes in the 1980s his imagined audience for the recordings was pretty small. With the possibility of online publication this audience has substantially increased.

Furthermore, through people uploading material to sites such as YouTube the amount of Daghestan’s culture that can be accessed on the internet continues to grow. Robert’s links with the academic community in Daghestan also means the recordings will gain exposure there as well.

It is no doubt that those interested in the cultural history of Daghestan will await the publication of these recordings with much excitement. When the website is available we will of course let you know!

***Many thanks to Robert Chenciner for talking to us about his collection, and to Stefan for putting us in touch***

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

Mouldy DATs

We have previously written on this blog about the problems that can occur when transferring Digital Audio Tapes (DATs).

According to preliminary findings from the British Library’s important survey of the UK’s sound collections, there are 3353 DAT tapes in the UK’s archives.

While this is by no means a final figure (and does not include the holdings of record companies and DATheads), it does suggest there is a significant amount of audio recorded on this obsolete format which, under certain conditions, is subject to catastrophic signal loss.

The conditions we are referring to is that old foe of magnetic tape: mould.

In contrast with existing research about threats to DAT, which emphasise how the format is threatened by ‘known playback problems that are typically related to mechanical alignment’, the biggest challenges we consistently face with DATs is connected to mould.

It is certainly acknowledged that ‘environmental conditions, especially heat, dust, and humidity, may also affect cassettes.’

Nevertheless, the specific ways mould growth compromise the very possibility of successfully playing back a DAT tape have not yet been fully explored. This in turn shapes the kinds of preservation advice offered about the format.

What follows is an attempt to outline the problem of mould growth on DATs which, even in minimal form, can pretty much guarantee the loss of several seconds of recording.

DAT Tape SizeTape width issues

The first problem with DATs is that they are 4mm wide, and very thin in comparison to other forms of magnetic tape.

The size of the tape is compounded by the helical method used in the format, which records the signal as a diagonal stripe across the tape. Because tracks are written onto the tape at an angle, if the tape splits it is not a neat split that can be easily spliced together.

The only way to deal with splits is to wind the tape back on to the tape transport or use leader tape to stick the tape back together at the breaking point.

Either way, you are guaranteed to lose a section of the tape because the helical scan has imprinted the recorded signal at a sharp, diagonal angle. If a DAT tape splits, in other words, it cuts through the diagonal signal, and because it is digital rather than analogue audio, this results in irreversible signal loss.

And why does the tape split? Because of the mould!

If you play back a DAT displaying signs of dormant mould-growth it is pretty much guaranteed to split in a horrible way. The tape therefore needs to be disassembled and wound by hand. This means you can spend a lot of time restoring DATs to a playable condition.

Rewinding by hand is however not 100% fool-proof, and this really highlights the challenges of working with mouldy DAT tape.

Often mould on DATs is visible on the edge of the tape pack because the tape has been so tightly wound it doesn’t spread to the full tape surface.

In most cases with magnetic tape, mould on the edge is good news because it means it has not spread and infected the whole of the tape. Not so with DAT.

Even with tiny bits of mould on the edge of the tape there is enough to stick it to the next bit of tape as it is rewound.

When greater tension is applied in an attempt to release the mould, due to stickiness, the tape rips.

A possible and plausible explanation for DAT tape ripping is that due to the width and thinness of the tape the mould is structurally stronger than the tape itself, making it easier for the mould growth to stick together.

When tape is thicker, for example with a 1/4 ” open reel tape, it is easier to brush off the dormant mould which is why we don’t see the ripping problem with all kinds of tape.

Our experience confirms that brushing off dormant mould is not always possible with DATs which, despite best efforts, can literally peel apart because of sticky mould.

What, then, is to be done to ensure that the 3353 (and counting) DAT tapes in existence remain in a playable condition?

One tangible form of action is to check that your DATs are stored at the appropriate temperature (40–54°F [4.5–12°C]) so that no mould growth develops on the tape pack.

The other thing to do is simple: get your DAT recordings reformatted as soon as possible.

While we want to highlight the often overlooked issue of mould growth on DATs, the problems with machine obsolescence, a lack of tape head hours and mechanical alignment problems remain very real threats to successful transfer of this format.

Our aim at the Greatbear is to continue our research in the area of DAT mould growth and publish it as we learn more.

As ever, we’d love to hear about your experiences of transferring mouldy DATs, so please leave a comment below if you have a story to share.

 

Posted by debra in audio tape, digitisation expertise, 0 comments

broken DAT / degraded mouldy tape

Early tape based digital formats such as DAT, Tascam DTRS and ADAT, etc are often problematic now, partly with tape issues and also reliability and spares availability. In 20 or even 10 years time these machines will be much less serviceable than the analogue tape machines of the previous generation and as a result more obsolete and a higher priority to migrate to a file based digital format.

We’ve also started to see a particularly nasty problem with some, and usually the 120 minute length, DATs. The first symptoms are a broken DAT tape usually on wind.  The tape pack seems to become slightly sticky, with intermittent tension between the layers of tape and with the thinner tape in 120 lengths this can sometimes break the tape on wind.

TDK 120 DAT sticky tape layers

You can see in the above image how the tape sticks slightly to the pack and then releases when hand wound. With the greater tension of a machine wind and the tape also wound around the head drum this becomes risky.

With large transfer jobs checking each DAT by disassembly is a mammoth task, but the permanent damage and / or part loss of a section of audio caused by a break is not feasible either!

Posted by greatbear in audio tape, 1 comment