While most diplomas and certification documents today are printed on archival paper produced from treated pulp or rag (cotton), if you have a diplomas that is many years old, it may well be made with sheepskin or parchment.
There are even a few institutions including
Wabash College that still give their graduates a sheepskin diploma.
Parchment is a thin material made from sheepskin, calfskin, or goatskin. It differs from leather in that it not tanned, but rather stretched, scraped, and dried under tension to create a stiff white, yellowish or translucent animal skin. The finest and highest quality parchments are also called vellum. For more detail about how parchment is manufactured, visit: http://en.wikipedia.org/wiki/Parchment.
So how can you tell if you have a sheepskin or parchment diploma? If you are given one, typically you will receive a note or explanation so that you know it is sheepskin. You can usually distinguish it by sight as well. A sheepskin document has a sheen to it that is greater than the polish on typical matte document paper. Sheepskin also tends to be more translucent and is prone to slight buckling or waves that are more noticeable than what we typically see with paper documents.
Example of a framed sheepskin diploma. Buckling may occur, and is considered normal, in sheepskin diplomas when exposed to changes in humidity.
If in doubt about what your diploma is printed on, it is always best to err on the side of caution and use archival mounting procedures that are recommended for sheepskin, and also happen to be equally safe for paper. In general, mounting a document so that it stays permanently flat by using heat or adhesive methods is not recommended. Many mounting procedures are irreversible, non-archival, and can cause discoloration or damage over time. In the case of sheepskin or parchment, whatever you do, do not try to iron it flat. The sheepskin can curl, melt, and be easily be destroyed by heat.
Documents, certificates and diplomas should be treated as a fine art original would be, using conservation quality backing board and mounting materials that are acid-free, lignin-free, and reversible. Museum mounting methods that are appropriate for sheepskin diplomas include: 1) professional hinging with wheat starch and Japanese paper on lignin-free 4 ply board, or 2) the application of archival corner pockets and/or mounting strips. In all cases, the document should be given room for natural expansion in response to humidity and natural temperature changes. Slight buckling of the skin in response to normal atmospheric conditions is considered normal for valuable documents. While it is not the preferred mounting method, in certain circumstances where the sheepskin has been rolled and stored in a small tube, heat mounting by an experienced custom framing professional is an option. It is done on a lower temperature setting with archival tissue that is reversible with heat.
In framing a sheepskin document, it is important that a conservation-quality window mat be used to keep the edges of the skin from curling up and touching the glass. If the document is allowed to be in direct contact with the glass, humidity can cause it to stick to the glass and create irreparable damage. Choosing your frame style is a matter of personal preference, but since this document will be a showpiece in your home or office for many years, choose a high quality frame that you really like.
If in doubt with regards to framing a sheepskin or parchment diploma, seek the advice of a Certified Picture Framer with the CPF designation through the Professional Picture Framers Association. For more information about the PPFA or to locate a qualified framer, visit: http://www.pmai.org/index.cfm/ci_id/33311/la_id/1.htm. In the event you have a sheepskin that needs repair or cleaning, consult a conservator who specializes in this field. To locate a conservator in your area, call the AIC (American Institute for Conservation) in Washington, DC at 202-452-9545 or visit http://aic.stanford.edu/public/select.html. For more information about custom framing a sheepskin diploma, visit http://www.pictureframingmagazine.com/pdfs/mastermount/JUL02_DIPLOMAS.pdf