Mouldy Tape

Mould infestation can present a significant problem for the digitisation of magnetic tape. Any evidence of mould growth should be taken seriously and affected tapes isolated.

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.


Hi. We have a mould issue on a 1″ C type video master. There’s significant visible white mould covering the exposed areas on the sides of the reel. The program is 91 minutes long. Is this something you can assist us with? If so any idea o pricing?

Ironically, the film is called QUARANTINE.

Thanks, Charles

Hi Charles

Thanks for your comment – I’ve replied to you by email.

Kind Regards


Michael Acton

I have a couple rap cassettes I bought recently, the mold is on the tape, but it’s also on the shell on the inside of it, do you guys do that too or no, cause I coukd clean the tape myself just hesitant abkut going inside the tapes, don’t wanna ruin them

Hi Michael

Yes, you’d need to clean the inside of the shell as mould can contaminate machines and other tapes.
You also need to be to check if the mould has caused the tape to stick together as this will damage the tape on playback..
Please wear a mask too and preferably do this outside as some mould spores can be hazardous….

Paul Maxwell

Hi Adrian
You sorted a couple of old studio demos for me, but I have now unearthed a VHS of us playing live at “the band on the wall” Manchester BUT it’s showing some form of infection through the windows on the tape and was wondering if this is something you may be able to clean / digitise this to a fob?

Hi Paul

Good to hear from you again – we’d be happy to help with your mouldy VHS tape.
I’ve sent you an email.


I sort of resell cassette tapes, and have had to ‘throw out’ many valuable tape d/t likely contamination from moulds (both visual or not). Is there any point in attempting to fix these? Also, some valuable ones have snapped from the reels upon rewind/fast forward. Is there a point, or does the cost of repair outweigh the value?


Hi Trevor

Thanks for your comment – we only clean mould from audio / video tape when the recordings are valuable and replay is needed.. Even with dedicated video tape cleaning machines mould spores if they’ve reached the tape surface are hard to remove in their entirety.

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