Safeguarding Opera Ballet Vlaanderen’s films and magnetic tapes affected by vinegar syndrome

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After making an inventory of audiovisual and digital archives in the performing arts sector, we came across a box containing film stock with a vinegar-like odour in the archive at Opera Ballet Vlaanderen. This raised our suspicions that it had been affected by vinegar syndrome, so we tested it using A-D strips and discovered this was indeed the case. The management team at Opera Ballet Vlaanderen therefore decided to transfer the affected materials to Cinematek for better storage, and asked VIAA to digitise the content so it could be safeguarded for the future.


  • 6/11/2015: film stock with vinegar-like odour discovered and reported
  • 2/12/2015: initial visual inspection and testing with A-D strips
  • 3/12/2015: discovery of the film stock reported to VIAA
  • 7/12/2015: evaluation of A-D strip test results
  • 22/12/2015: test results reported to Opera Ballet Vlaanderen, with proposed solution
  • 30/12/2015: confirmation from Opera Ballet Vlaanderen that they are taking the necessary steps for a solution
  • 05/01/2016: confirmation that film stock has been transferred to Cinematek
  • 06/01/2016: VIAA informed about test results and storage at Cinematek


In the first half of 2015, Het Firmament, Flanders Arts Institute and PACKED vzw took the initiative to make an inventory of audiovisual and digital archives in the performing arts sector. (For more information, see Making an inventory of the audiovisual and digital archives in the performing arts sector (current situation) – in Dutch. Around 170 performing arts organisations were contacted with regard to this inventory, including Opera Ballet Vlaanderen. The inventory took place in consultation with VIAA, which was founded by the Flemish government in 2012 to sustainably preserve Flanders’ digital cultural heritage and make it possible to access the content. (For more info, see the website van VIAA VIAA website. As suggested by Het Firmament, Flanders Arts Institute and PACKED vzw, VIAA has also been digitising audiovisual archives and preserving digital archives and collections from the performing arts sector as part of its strategic plan since 2016.

On 6 November 2015, Het Firmament reported to PACKED vzw that it had found a box containing film stock during one of its visits to Opera Ballet Vlaanderen’s archive as it continued to make the performing arts sector inventory. This box probably dated from before 1970 and had a vinegar-like odour.

PACKED vzw therefore suspected that this film stock had been affected by vinegar syndrome. Vinegar syndrome is a deterioration process that can affect films, magnetic tapes and photographic negatives/slides with an acetate base. The decay is autocatalytic, which means the deterioration starts slowly (because there’s still only a small amount of the acid that causes it), but quickly accelerates as the chemical reaction continues. The autocatalytic point is the moment when the reaction starts to accelerate exponentially. The base layer of the acetate film or magnetic tape acidifies, which emits a vinegar-like odour and the material becomes brittle and starts to shrink. A high temperature and fluctuating but relatively high level of humidity in the storage environment speed this process up further. If a vinegar-like odour is detected, the film or magnetic tape is already in an advanced state of decay. The deterioration process starts much earlier, however, and can only be detected in its early stages with the use of e.g. A-D strips (see below).

Vinegar syndrome cannot be reversed; it can only be delayed by storing the affected materials in suitable conditions. Affected acetate films also need to be stored separately to prevent other carriers with an acetate base from also being affected. It is recommended to copy the content stored on the affected films and magnetic tapes to a new carrier, or to digitise it, to ensure it does not become lost.


Identify the stock and investigate its condition

The first step was to confirm that the film stock had indeed been affected by vinegar syndrome. There are three different ways of doing this.

1. Vinegar syndrome is named after the smell of acetic acid (in vinegar), which is created when the acetate base layer in films deteriorates. If you can smell vinegar in an archive, it’s very likely that one or more films, magnetic tapes or photographic negatives/slides have already started to decay. This smell was detected when Het Firmament discovered the film stock.

2. Films and magnetic tapes affected by vinegar syndrome often have visually identifiable symptoms:

  • shrinkage;
  • curling and warping (no longer flat);
  • loss of flexibility (no longer so evenly or tightly wound);
  • signs of cracking or warping on emulsion surface;
  • white powder near edges (as the binding layer decays).

3. A third way of finding out if films and magnetic tapes have started to decay as a result of vinegar syndrome is to test them using A-D strips. A-D strips are dye-coated paper strips which can be used to detect vinegar syndrome in collections and assess how advanced it is. The paper strips need to be placed in a sealed can, bag, box or locker together with the films, magnetic tapes or photographic negatives/slides, where they will change colour according to the acid gas produced by the decaying acetate base.

In order to confirm that the film content had indeed been affected by vinegar syndrome, employees from PACKED vzw and Het Firmament went back to the Opera Ballet Vlaanderen archive on 2 December 2015.

All the film cans and boxes were opened. Closer inspection showed that they didn’t just contain photographic film reels (mostly black and white 16mm, probably reversal film) but also some magnetic audio tapes (sepmag). A number of the film cans showed signs of rust, including on the inside. A number of film reels were not in film cans, but in plastic bags. As well as the vinegar-like odour, we also noticed that some film reels and magnetic audio tapes had visible signs of decay (e.g. curling and warping).

Image 1: a film reel that has warped because of vinegar syndrome
Image 2: a magnetic audio tape with visible signs of vinegar syndrome
Image 3: a rusty film can

We found the following film stock in the cardboard box:

  • 47 x 16mm black and white films;
  • 23 x 16mm magnetic tapes;
  • 4 x 35mm black and white films.

We also found labels indicating the contents of the film stock on and in some film cans and boxes. The labels contained information such as 'Jazzles Kurt Joos', 'Lydia Chagoll', 'Repetitie Romeo & Julia - Béjart - Ballet XXe eeuw - nov 1966', 'Maurice Béjart - Mis van Onze tijd', 'Interview Jeanne Brabants - Lea Daan', 'Interview Serge Lifar - Parijs - Deel 1', and also a couple saying 'Jazzmedley', 'Ballet' and 'Ballet voor debutanten'. We weren’t able to verify if the descriptions on the labels corresponded with the content on the photographic film and magnetic audio tapes because we didn't have the right playback equipment available.

We placed around 60 Danchek A-D strips in the film cans, boxes and plastic bags in total. These paper strips then immediately started to change colour. It’s then best to keep them in the sealed film cans, boxes and plastic bags for a minimum of 24 hours, depending on the storage conditions.

We only opened the containers again five days later. All the paper strips appeared to have changed colour dramatically. Comparing these colours with the reference values provided by Danchek indicated that all the newly discovered film stock had already passed the autocatalytic point. It all appeared to be at stage three, and therefore needed to be copied to new carriers or digitised to safeguard the content for the future – very urgently for the most part.

Image 4: reference values for the Danchek A-D strips
Image 5: used A-D strips on the left, unused A-D strip on the right

Magnetic tapes are not only susceptible to vinegar syndrome; almost all are also susceptible to sticky shed syndrome. This is a condition whereby the base layer on the magnetic tape – which binds the magnetised iron oxide coating to the plastic carrier – has deteriorated so much that it no longer has sufficient adhesive strength, and the magnetic coating comes loose and peels away when played back. This separation of particles causes a brief loss of audio signal on the audio tape (or video signal for video tapes). Magnetic tapes like this can require specific treatments such as ‘tray drying’ before they can be digitised. Just like vinegar syndrome, sticky shed syndrome is also influenced by the conditions the magnetic tapes are stored in. Because it was very clear that all the magnetic tapes had already been affected by vinegar syndrome, there was no need to carry out further checks for the presence of sticky shed syndrome.

Relocating the affected stock

It was also clear from the visit that took place on 2 December 2015 that the affected film stock was being stored in less than optimal conditions. The only way to slow down decay caused by vinegar syndrome is better storage conditions, i.e. at a low (constant) temperature with low relative air humidity. In order to prevent other film stock, magnetic video or audio tapes, and photo negatives and slides from deteriorating further, the affected film stock had to be isolated.

Organisations such as Opera Ballet Vlaanderen do not specialise in storing photographic film and magnetic audio tapes affected by vinegar syndrome. This is why PACKED vzw and Het Firmament suggested depositing the stock with Cinematek – a company that does specialise in storing this (affected) film stock – when the test results were conveyed to Opera Ballet Vlaanderen’s management on 22 December 2015.

At the same time, we also informed VIAA about the discovery of the film stock and test results. This meant this new content could be included in the list of affected film stock to be considered for digitisation by VIAA. VIAA and Cinematek work together on film digitisation; Cinematek writes descriptions and condition reports for the affected film stock for VIAA, which are then used to determine the priority for digitisation.

The Opera Ballet Vlaanderen management team agreed to this suggestion and the necessary steps are now being taken to transfer the film stock.


  1. An initial visual inspection of the materials gave a rough indication of its technical properties and content.
  2. Testing with A-D strips established with certainty that the film reels and magnetic audio tapes had been severely affected by vinegar syndrome.
  3. The management team at Opera Ballet Vlaanderen has been made aware of this fact, and convinced about the severity of the situation.
  4. VIAA has been contacted so that the stock can be included in the list of content to be digitised.
  5. The Opera Ballet Vlaanderen management team has contacted Cinematek and taken the necessary steps to relocate the stock.

This is the first important step when following the TRACKS guidelines:

Authors: Rony Vissers (PACKED vzw), in collaboration with Eline De Lepeleire (Het Firmament)