Posts tagged ‘deterioration’

June 1, 2011

Images of base film shrinkage (buckling or channeling)

Images from various websites and resources (not our own)

June 1, 2011

Images of redox

collected from various websites

May 20, 2011

using A-D strips

A-D (acid-detecting) strips are acid-base indicator papers that turn colors in the presence of increasing amounts of acidic vapors, in this case from acetic acid from the chemical decay of an acetate film base. Often acetic acid has a vinegary smell, but the strips provide a more accurate and safer method of evaluating acetate deterioration than sniffing!

appropriate placement of A-D strips (from IPI's user guide)

  1. Remove the film from the box. We will not test inside the box in order to avoid inaccurate results based on old, reused boxes (which we are planning to discard anyway) and in order to create a closed, confined space in which the strip will test for acidic vapors created by the deterioration of the film.
  2. Place a single roll of film and one A-D strip inside a plastic bag. Be sure the strip does not slide inside the rolled film because the strip must be exposed to atmosphere within the enclosed space, but it is okay (even preferred) to put the strip against the edge of the film between flanges of the roll (image shows preferred placement of strips but this might not be possible with many of our film)
  3. Seal the bag with some air inside it.
  4. Tape the relevant information from the box to the bag.
  5. Leave the strip with the film for at least 24 hours (exposure for a few days is preferred). At the end of the exposure period, if you can see through the sealed bag that the color change on the strip is not uniform, then the color change process may not be complete and you should leave it for a while longer.

IMPORTANT: After opening a package, please try to use all the A-D strips. If you can not, then please seal the unused strips inside the resealable polyethylene bag and within the outer bag as soon as possible.

When you are ready to catalog the film,

  1. Enter basic information into a new record in the database.
  2. When you open the bag, remove the A-D strip first.
  3. Compare the strip’s color to the color bands on the pencil. Exact matches will not always happen. Even though only 4 levels (0-3) appear on the pencil, think in terms of 7 possible values: 0, 0.5, 1.0, 1.5, 2.0. 2.5, or 3.0 If the strip’s color is close to one of the bands but not quite there, go ahead and take the number that the color seems similar to. If the strip’s color seems to fall between two color bands, then assign it a value halfway between the numbers.
  4. Record the number in the “A-D Strip Level”  field in the database.

Worried because the A-D strip number seems to contradict  your own inspection of the film? Don’t be!

You see clear signs of deterioration (channeling, for example) but the A-D strip value seems low?  The acidity can evaporate from film over time.

When you examine the film base, you believe it is polyester, yet the A-D strip gives a value? Polyester-based films can absorb acid vapors from deteriorating acetate-based neighbors or from reused boxes that absorbed it from earlier contents.

May 16, 2011

“Condition of microfilm” field – appropriate terms

Terms that can be entered into the “Condition of Microfilm” field in the database are in BOLD

Issues with the surface of the film

abrasion = damage to the surface of the film caused by rubbing, scratching, etc.

crystals on the surface of the film or the roll


mold: bring to the attention of Deb, Sarah, or Sheila immediately!

moisture spots

damage from a rubber band or metal objects, including specifically rust

paper adhering

brittle tape or yellowed tape – if you acted to improve this issue, please add “-new splicing tape applied

Issues with the emulsion layer (the one containing the image)

mirroring = usually bluish-metallic sheen, sometimes has an iridescent quality; in extreme cases, can appear bronze-colored

redox (reduction-oxidation reaction, aka microspots) = red or colored blemishes on film, resemble measles

with regard to image decay, please make a note if you think you see any of the following:

color bleed

color fading

image discoloration = usually yellowing of the image itself (but not apparently of the film base)

Issues with the base layer or the physical condition of the film as a whole


flaking = localized separation between the base and emulsion layers, usually along the edges

bubbling = “bubbles” appear between the layers

buckling = base clearly separating from the emulsion layer in several places

channeling = extreme form of buckling where the base has separated significantly from the emulsion layer and the film is very warped and brittle

warped = badly out of shape, perhaps bent from handling, but layers are not significantly separating

curling (width) or curling (length)

film torn – if you repaired this problem, please add “-repaired with splicing tape

vinegar syndrome

adhesion = film adhering to itself, unable to separate without risk of loss

May 10, 2011

acetate vs. polyester film bases

In general, there are three types of film bases commonly used for microfilm: cellulose nitrate, cellulose acetate, and polyester. Fortunately, we do not believe that any of our microfilm are the flammable nitrate type, but it is likely that a fair number – especially our older microfilm – are of acetate which deteriorates over time.

During your visual inspections of the film, please try to identify the film base and any signs of deterioration.

Most of the information below can be found on the NEDCC website: and

NITRATE – used from ca. 1890-1950s. Some signs:

  • Sometimes it can be identified if manufacturers stamped the information along an edge
  • It curls into very tight rolls as it deteriorates. Further signs of deterioration described below.
  • When viewed through the polarizing filters, nothing will show (the same is true of acetate but polyester-based film will seem iridescent).

From NEDCC website (Monique Fischer):

“Cellulose nitrate decomposition can be very rapid. Deterioration is generally categorized in six progressive stages:

Level 1 No deterioration.
Level 2 The negatives begin to yellow and mirror.
Level 3 The film becomes sticky and emits a strong noxious odor (nitric acid).
Level 4 The film can become an amber color and the image begins to fade.
Level 5 The film is soft and can weld to adjacent negatives, enclosures and photographs.
Level 6 The film can degenerate into a brownish acid powder.

Most negatives will retain legible photographic detail into the third stage of decomposition. These negatives may become brittle, but with careful handling can be duplicated. Negatives in the fourth, fifth, and sixth stages of decomposition generally have no legible image and should be either placed in cold storage or duplicated.”


ACETATE (aka SAFETY FILM)  – most commonly used from 1920s-1970s, some stock still available through 1980s. Some signs:

  • Sometimes it can be identified if manufacturers stamped the information along an edge (might be labelled “Safety” instead of “acetate”)
  • When you hold a tightly wound roll up to the light and look through the side of the film, it is likely acetate if it appears opaque.
  • When viewed through the polarizing filters, it appears opaque (the same is true of nitrate but polyester-based film will seem iridescent).
  • A-D (Acid-Detecting) strips can detect acetic acid that is a sign of deteriorating acetate film base. After period of exposure to the film in an enclosed environment, the color of the strip will indicate  the extent of deterioration. The strips should show no signs of deterioration with polyester-based film, which is chemically more stable than acetate.
  • It smells like vinegar during some states of its deterioration.
  • It sometimes curls across the width of the film. Further signs of deterioration described below.

From NEDCC website (Monique Fischer): “Deterioration is generally catalogued in six progressive stages:

Level 1 No deterioration.
Level 2 The negatives begin to curl and they can turn red or blue.
Level 3 The onset of acetic acid (vinegar smell); also shrinkage and brittleness.
Level 4 The warping can begin.
Level 5 The formation of bubbles and crystals in the film.
Level 6 The formation of channeling in the film.

POLYESTER – most commonly used after 1970sSome signs:

  • When viewed through the polarizing filters, it appears iridescent (acetate and nitrate will appear opaque).
  • When you hold a tightly wound roll up to the light and look through the side of the film, polyester-based film will be slightly translucent and allow light through.
  • Because it is chemically stable, the A-D strips should not change color.