Identifying laminated papers

When assessing a collection that may contain laminated materials, the first step is simply to determine whether or not the materials have been laminated. Papers laminated with cellulose acetate can vary in appearance, but the easiest way to tell if a piece of paper is laminated is just to examine it closely. If an object was laminated without tissue, the cellulose acetate laminate should be transparent, often with a shiny plastic look (Figure 8). The paper itself may have taken on a translucent quality. If tissue was incorporated during lamination, the surface should look dull or hazy (Figure 9), as if the entire object is seen through a filmy cloud. Depending on the platen that was used to apply pressure during the lamination process, the surface of the object may be smooth or patterned, often with what looks like a cloth weave (Figure 10).

After lamination, most documents were left with a narrow border of laminate and tissue. These cloudy borders may extend up to an inch from all sides of the sheet of paper, although they were often trimmed to within 1/16” of the edge of the paper (Figure 11). Such borders, which were considered desirable as a means of increasing protection for the paper and making leaves easier to bind together, are tell-tale indications of lamination. Cellulose acetate lamination is only one of a host of methods that have been used in attempts to strengthen paper documents. Other treatments may look similar superficially, so it is important to examine papers carefully.

In addition to examining the objects themselves, it may be possible to find documentation about their treatment. Treatment reports, if they exist, should discuss the lamination process. In the absence of formal reports, financial records such as purchase orders or invoices may indicate which documents were laminated, particularly if the lamination was contracted with an outside party. In some cases, knowing when or where an object was laminated may provide valuable information about the materials and the process that were used; however, there was considerable variability in the lamination procedure, even over a short time frame within a single institution. The most important information remains the condition of the object itself.

 

Determining condition

To determine the condition of laminated objects, carefully observe the collection. Signs of damage or deterioration include:

Pigments or inks that have smeared, run, or melted. Damage to pigments and inks has occurred during the lamination process, either through excessive heat and pressure or through chemical reactions prompted by the process. If the document lacks other signs of damage, it may currently be stable (see Figure 2).

Scorch marks or burning. Scorching indicates that the document was damaged by excessive heat during the lamination process. If other signs of damage are not present, the object may currently be stable.

A strong vinegar or ammonia odor. A vinegar, ammonia, tobacco, or cardboard odor indicates that the cellulose acetate has begun to break down. Vinegar syndrome is a sign of active deterioration, which cannot be stopped once it has started. Any object with vinegar syndrome poses a direct threat for nearby collections, as the off-gassing process may cause formerly stable objects to begin deteriorating.

Damaged laminate Laminate that has warped, stretched, curled, bubbled, cockled, or peeled away from the paper either was not applied properly or has begun to deteriorate. As the plastic deforms, it places stress on the paper encased within it. In extreme cases, it may literally tear the paper apart (see Figure 5).

Discolored or yellow paper. Discoloration suggests that the object was not deacidified prior to lamination and is at risk of damage from acids present in the paper (see Figure 4).

Stiff or brittle laminate. Embrittlement is caused by inherent chemical changes in the laminate, including deterioration of plasticizers. As the plastic becomes less flexible, the object will be increasingly vulnerable to tears and other mechanical damage.

Chipping, cracking, or snapping. Whether involving the laminate or the document, this extreme form of embrittlement places corners, bound edges, and other vulnerable areas of the document at risk of becoming detached and eventually lost. The document is quite fragile, and literally in danger of falling to pieces if handled.

Sticky or oozing surfaces. This indicates that plasticizers are exuding from the laminate, placing the document at risk of sticking to other objects. In the worst case, pages may be adhered in a block, making them unusable.

Pressure-sensitive tape or other inappropriate treatments. Some documents were repaired with pressure-sensitive tape before lamination; as the tape degrades, it will damage the document. Unless they were done by a qualified conservator, repairs to documents after lamination can also pose a risk to objects (see Figure 12)

 

Signs of Stable Laminate

If laminated items do not have visible damage, are flat with little to no planar distortion, and have little to no noticeable odor, they can be considered stable. Remember that the lamination process was quite variable, so even objects within the same manuscript may differ greatly in condition and conservation needs. To put it plainly, no two laminated documents will react alike. Some may remain stable for long periods of time, while others may rapidly degrade and endanger other objects.

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Figure 8. This document shows the shiny plastic look common in laminated papers. 18th century land grants from the Pennsylvania State Archives

Figure 9. This page shows the dull, hazy look of lamination with tissue and a matte laminate. Ledger book, 1866 By Roman Nose, Lakota

Figure 10. Detail of laminated document, showing high surface gloss and some paper texture. 18th century land grant from the Pennsylvania State Archives

Figure 11. This small sheet of notes shows the narrow, cloudy border of laminate around the sides of the document. Maps and notes on place names on the Baffin Island coastline, 1883 Franz Boas.

Figure 12. A map mended with black tape prior to lamiantion. The products of the tape's deterioration will be trapped within the laminate, causing damge to the paper. 18th century land grant from the Pennsylvania State Archives.

Figure 13. An example of appropriate archival storage in archival boxes and cabinets, with a stable environment. Artwork storage for the National Anthropological Archives.