Materials & standards
What we mean when we say archival
“Archival” is not a regulated word. Anyone can print it on anything. This page sets out what we actually mean by it, product by product, so that you can check our claims against your own requirements rather than taking the word on trust.
pH, buffering, and the mistake that matters most
A neutral material is one that is not itself acidic. A buffered material goes further: it carries an alkaline reserve, normally calcium carbonate, which neutralises acids that migrate into it — out of the object it houses, and out of the air in the room.
For paper, that reserve is protective. Paper degrades by acid hydrolysis, it generates its own acids as it ages, and a buffered enclosure slows that down measurably. This is why a mount cut from buffered museum board does not print a brown bevel line onto a print in thirty years, and a woodpulp mount reliably does.
For protein-based material the same reserve is harmful. Wool, silk, leather, parchment, feather — and most photographic processes with a gelatin binder — are damaged by an alkaline environment. Housing them in buffered stock is among the most common specification errors in collection care, and among the quietest: nothing appears to go wrong for a long time.
| If the object is | Specify | Because |
|---|---|---|
| Paper — documents, prints, books, records | Buffered | the reserve neutralises acids the paper generates as it ages |
| Wool, silk, other protein textiles | Unbuffered | alkalinity degrades protein fibre |
| Leather, parchment, vellum, feather | Unbuffered | as above |
| Photographs with a gelatin binder | Unbuffered | the binder is protein |
| Mixed or unidentified collections | Unbuffered | it is the option that is safe against everything |
Because buffered and unbuffered board are indistinguishable once they are on a shelf, every unbuffered sheet we sell is edge-marked UNBUFFERED along one long edge and wrapped in a contrasting colour. If you hold both, keep the wrapping on and keep them apart.
Reversibility
Conservation work is done on the assumption that someone will need to undo it. That is not pessimism; it is the only honest position to take about a treatment whose long-term behaviour nobody has observed yet. So the adhesive matters more than almost anything else in the repair.
| Adhesive | Reversible with | Use it for |
|---|---|---|
| Wheat starch paste | water alone | tissue repairs, hinging, anything touching the object |
| Methyl cellulose | water alone | low-tack hinging, poultice, size, consolidation |
| Neutral-pH PVA | not reversible | housings and structure only — never on an object |
PVA is in the catalogue because boxes, cases and spine linings need a strong flexible bond that sets quickly, and starch paste is the wrong tool for that. It is not in the catalogue as a repair adhesive, and we would rather say so on this page than let the distinction go unstated.
We do not sell pressure-sensitive tape for repair, in any grade, under any description. There is no version of it that belongs on an object.
Fibre and manufacture
- Museum board — 100% cotton fibre, four-ply solid throughout. Not a surface paper laminated over a grey core, which is what “conservation board” sometimes means.
- Binder’s board — calendered, not laminated. A laminated board delaminates at the fore-edge under decades of handling; a calendered one does not.
- Repair tissue — 100% kozo, long bast fibre, so a torn patch feathers into a soft boundary that distributes stress instead of concentrating it at a cut line.
- Endpaper — mould-made, four deckles, neutral pH, internally sized, with the grain direction stated because a cross-grained endpaper cockles at the first paste.
- Blotter and interleaving tissue — cotton, unsized, no optical brightening agents. Brighteners fluoresce and will confuse anyone later examining the object under UV.
- Leather — vegetable-tanned only. Chrome-tanned leather is unsuitable for work intended to last, and the tannage is the first thing a conservator asks about.
- Linen thread — unbleached. Bleaching costs strength and adds residue.
- Polyester sleeves — inert polyester film, never PVC. PVC off-gasses hydrogen chloride as it degrades and acidifies whatever is sealed inside it.
Two limitations we would rather you heard from us
Polyester sleeves are wrong for friable media. Charcoal, pastel, flaking pigment and similar surfaces are lifted by the static charge in the film. Those want a folder, not a sleeve.
Pyroxylin-impregnated buckram does not take starch paste well. That is a property of the fill, not a fault in the cloth. Use PVA with it, or specify the starch-filled cloth instead.
What we do not claim
We do not claim compliance with any particular institutional standard on your behalf, because standards are written for a use and we do not know yours. What we publish is the fibre, the pH, the buffering, the tannage and the manufacture, so that you can check our material against the standard you actually have to meet. If you need a written specification for a tender or a grant application, ask and we will send what we hold on the line.