Tracking Acidity in Your Collection

A-D Strips are used to identify the presence of vinegar syndrome in a collection containing cellulose acetate, predominantly in reel format, though they can be used to identify negatives with vinegar syndrome.

What are they? They are made of dye-coated paper that changes colour when exposed to low pH. A-D Strips detect the presence of acetic acid, the culprit behind vinegar syndrome. Acetic acid vapour is released from degrading cellulose acetate. As the released vapour comes into contact with the A-D Strips, the strips change colour. The colour change is dependent on the concentration of acetic acid detected. Unaffected strips begin as the colour blue, and slowly migrate to blue-green, green, green-yellow, and finally to bright yellow upon exposure.

How should they be used? A-D strips can be placed in film or audio canisters, boxes, or bags. For negatives housed in boxes, it can be easier to monitor acetic acid vapours by suspending the A-D Strips along the top of the box, rather than the placing them at the bottom.
You will need: linen tape, two-sided tape, cotton string, and A-D Strips

  1. Use linen tape to adhere cotton string across an open box containing cellulose acetate negatives.
  2. Use two-sided tape to adhere A-D Strips to the string, dye-coated side facing down towards the negatives.
  3. Put the lid back on the box, and return in one week to monitor the colour change of the A-D Strips.
A-D Strips - Negatives

Image Credit: Emily Turgeon-Brunet

 

Please visit the Image Permanence Institute’s webpage on A-D Strips for more information: https://www.imagepermanenceinstitute.org/imaging/ad-strips

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