Comparing Parchment, Paper, and Vellum: A Quick Guide for Curators and Researchers

A deed on parchment, a ledger on rag paper and a charter on vellum can arrive in the same week, in identical grey boxes, looking broadly alike to anyone who has not handled all three. They will not want the same things from you. One will forgive a fortnight in a dry room. Another will cockle at the corners and never quite lie flat again. Knowing which is which before you lift the lid is the difference between routine care and an unnecessary intervention.

What the three words actually mean

Parchment is animal skin — most often sheep or goat, occasionally calf or pig — that has been limed, dehaired, stretched and dried under tension. It is not leather. Leather is tanned; parchment is deliberately kept from tanning so that the collagen network stays open, pale and responsive to moisture. That responsiveness is the whole story of its care.

Vellum is a grade rather than a separate species. Strictly, it is calfskin, and in practice the word describes the finer, thinner, whiter skins in a workshop's output. Usage drifts by country and century: what a nineteenth-century English stationer sold as vellum may be a prepared skin of almost any young animal origin. When you are unsure, write "skin support" in the record and add what you can actually see. Precision about uncertainty is better than a confident error that misleads the next person.

Paper is a different material altogether: a matted sheet of cellulose fibre, in Europe made from linen and cotton rags until the middle of the nineteenth century, and increasingly from wood pulp afterwards. The fibre source matters enormously, because groundwood brings lignin with it, and lignin is what turns a newspaper yellow and brittle within a few decades.

Telling them apart takes a lamp and a little patience. Raking light shows the follicle pattern and vein traces of a skin; transmitted light shows the chain lines and laid wires of a paper mould. Skin edges are rarely cut clean and square. Vellum is often translucent in a way no paper of comparable weight manages.

Making a skin: lime, tension and a crescent knife

The traditional sequence is unglamorous and slow. Skins are soaked in lime liquor to swell the fibre and loosen hair, then scraped on a beam with a blunt knife. The clean skin goes onto a wooden frame, held by cords or laced edges, and is stretched while it dries. Only when it is taut and dry is it thinned from the flesh side with a crescent-shaped blade, then pounced with pumice and whiting to give a surface that will take ink.

Every one of those steps leaves a consequence in the object you are holding. Because the skin dried while stretched, its fibre network carries a memory of that tension. Raise the relative humidity and the fibres relax and try to shrink; lower it and they stiffen. This is why a parchment document undulates, why its edges can become rigid and wavy at once, and why a sheet that has been pressed flat for years will buckle again the moment conditions change.

Making paper: rags, moulds and size

Rags were sorted, retted and beaten to a pulp, then lifted in a vat on a wire mould bearing a watermark. The wet sheet was couched onto felt, pressed, hung to dry, and finally sized by dipping in warm gelatine so that ink would not feather into the fibre. That surface size is a coating, and coatings wear out. It also explains a common finding in eighteenth-century correspondence: iron gall ink that once sat crisply on the surface has, over centuries, eaten into the paper beneath it.

Where each support fails

Parchment and vellum

Time is rarely the main enemy. Fluctuating humidity is. A skin that swings between damp and dry several times a season will develop pronounced undulation, translucent gelatinised patches from old moisture exposure, and edges that crack when handled. Iron gall ink becomes dangerous here, because it does not flex with the skin: where a tight curl forms, the ink sits on the outside of the curve and flakes away in small, heartbreaking losses.

Two habits do most of the damage in collections. The first is pressing: flattening a cockled skin under weight redistributes strain rather than removing it, and often cracks ink along the crests of the waves. The second is framing a skin tightly behind glass in a room with daylight. The glazing traps a small, hot, unstable microclimate, and the skin responds to it all summer.

Paper

Paper fails chemically as well as physically. Acid hydrolysis and oxidation make sheets brittle and discoloured; metal ions in the fibre, plus moisture, produce the familiar brown freckling called foxing; residual adhesive from old repairs stains and stiffens; mould blooms wherever damp is allowed to persist. Rag papers can stay supple for five hundred years. Wood-pulp sheets of 1890 can be beyond handling. If two books look equally old, check the paper before you decide which one needs the phase box.

A quick reference by material

• Parchment (sheep, goat): strong, springy, highly hygroscopic. Wants stable humidity, flat support without pressure, and no tension of any kind.
• Vellum (calf): thinner and finer, therefore more reactive to moisture and more easily distorted by framing and by handling with warm hands.
• Rag paper: usually robust and forgiving. Watch iron gall ink, old adhesives and the inevitable edge tears.
• Wood-pulp paper: brittle, yellowing, often beyond repair at the margins. Handle less, house sooner, and copy the content.
• Composite objects — a parchment text block sewn onto paper endleaves, or paper pasted to a skin cover — need the stricter of the two sets of conditions, not an average.
• If you cannot decide: photograph the surface in raking light, describe what you see, and ask a conservator before doing anything wet, adhesive or flattening.

Housing, display and the small decisions that add up

Store flat when you can. Parchment belongs in a shallow box that supports the whole sheet, with unbuffered archival board and interleaving rather than buffered materials, which are more comfortable for paper than for skin. Never force a skin flat to make it fit a standard box; make the box fit the object. If a large document must be rolled, roll it loosely on a tube of generous diameter, roll with the flesh side outward, and interleave so surfaces do not abrade.

Monitor the room before you blame the object. A week of logged relative humidity and temperature will tell you more than an hour of inspection, and stability matters more than hitting a particular number. Keep light exposure modest and cumulative, filter ultraviolet, and do not leave skins on long-term display behind ordinary glass in a sunlit gallery. For paper, watch the storage boxes near outside walls and the shelves below pipes.

Before your next survey: a short checklist

1. Identify the support first — lamp, raking light, transmitted light, edges — and record what you saw, not what you assumed.
2. Photograph each item in raking light at a fixed distance so that later comparisons mean something.
3. Note old repairs, adhesives and previous flattening attempts, and leave them alone.
4. Log the store's humidity and temperature for a week; deal with the room before the object.
5. Choose housing per material: unbuffered, supportive and pressure-free for skins; standard archival board for most papers.
6. Decide whether a display mount can follow the object's existing shape instead of correcting it.
7. Call a qualified conservator early for anything involving humidification, flattening, tape removal or ink consolidation. Early advice is cheap; reversing a well-meant treatment rarely is.

None of this requires a laboratory. It requires knowing which of the three materials is in front of you, and then resisting the instinct to make it neat. A slightly undulating parchment that is stable, housed and undisturbed is in better condition than one that lies perfectly flat because someone once left it under a weight for a year.

Photo: ChrisFiedler / Pixabay