Glassine

Lauren Jones <collectionscare [at] rhqre__co__uk> writes

>...  I have read recently that glassine could be used as a
>slip sheet for between prints and drawings (Margaret Holben Ellis'
>Care of Prints and Drawings).  But when I mentioned this to a
>visiting conservator, she was a bit dubious about its use.  So, can
>anyone confirm the good or bad points of using glassine, I have now
>purchased a huge roll, at some expense, from Preservation Equip Ltd
>UK who pitch it as "transparent, smooth with a pH of 7.0,
>unbuffered..."

Having proffered the advice to use neutral glassine for interleaving
works on paper, I feel obliged to respond.  Since that time (1987!)
I haven't seen any other candidates for "slipsheets" that are
clearly better for general use; as Ms. Jones notes, every material
has its pros and cons.  Neutral glassine (*not* the type with a
greenish cast which is often used to wrap paintings) is
smooth-surfaced, neutral, translucent (allowing for easier
identification of what is below), does not cockle or wrinkle easily
and is relatively inexpensive.  Because it does not contain a
buffering   agent, neutral glassine will not remain neutral
indefinitely, especially if placed in contact with acidic materials.
It should be replaced periodically.  A stack of pre-cut standard
sized sheets placed in Readings Rooms or Storage Vaults usually
encourages rotation or slipsheets can be replaced during periodic
inventories or surveys of collections.

Used for interleaving, Mylar has the advantage of being transparent
(allowing for rapid identification of what is below) and smooth,
however, it generates considerable static electricity and has sharp
edges and corners.  Plus it is a heavier material - a storage box of
items interleaved with Mylar can be quite heavy.  It is also more
expensive (and not particularly good for the environment).

"Silk" tissue (gampi) is very smooth and light weight, but is hard
to handle and wrinkles and cockles easily.  It not as translucent as
glassine and can be of questionable pH.  It does not contain a
buffering agent so it also needs to be replaced periodically. Abaca
is the most recent fiber used in what resembles "silk" tissue. Abaca
tissue is light-weight, neutral, unbuffered and non-abrasive tissue;
it is frequently used in textile and costume storage.

"Buffered" tissue, which contains a calcium carbonate reserve, is
slightly abrasive and is not translucent.  It wrinkles and creases
more easily than glassine, but less so than silk tissue.  It will
stay alkaline for a longer period of time (again depending on the
acidity of its surroundings.).  A heavier (5 pt.) buffered paper is
also available which can be used for interleaving and can also be
made into enclosures.

Some photographic materials (albumen, cyanotype, dye transfer, and
chromogenic color prints) should not be stored in contact with
alkaline slipsheets.  Smooth-surfaced, neutral interleaving paper
and tissue have been developed specifically for use in photograph
collections.  These are perfectly acceptable for use in
non-photographic collections, however, they are more expensive,
heavier and not translucent.

Clearly many factors enter into the decision of what materials to
use for interleaving a collection of works of art on paper.
Large-format or heavily used items may need the additional support
provided by Mylar or a heavier archival-quality paper that can be
fashioned into a folder; highly acidic works may benefit from the
extra protection afforded by an alkaline slipsheet.  At the end of
the day, however, it strikes me that neutral glassine remains a
versatile, affordable and safe option.  But the rolls can be
unwieldy.

Margaret Holben Ellis
Conservation Center
Institute of Fine Arts
New York University
Thaw Conservation Center
Morgan Library and Museum


                                  ***
                  Conservation DistList Instance 26:51
                   Distributed: Tuesday, May 28, 2013
                       Message Id: cdl-26-51-002
                                  ***