Reference
Glossary
Plain definitions of the words framers, suppliers and conservation publishers use, with the chapter that explains each one in full.
Three kinds of word turn up in this subject, and it helps to know which you are reading. Some are measurements, which mean the same thing everywhere. Some are trade terms, which mean what a shop means by them. And some are adjectives, which commit nobody to anything; those are marked.
| Term | What it means | Where it is explained |
|---|---|---|
| Acid free | An adjective, not a specification. A pH reading does not qualify a material, and some board that is alkaline when made becomes acidic quickly. The trade body that publishes the board standard says the term must be avoided in product specifications | The words |
| Acid mat burn | The brown or yellow line left on a sheet where an acidic window mat sat. A federal leaflet names the cause: a mat of colored papers over a groundwood core | Reading the condition |
| Alpha cellulose | Wood pulp chemically refined to remove lignin and hemicellulose. Boards made from it are often sold as conservation board | Board grades |
| Archival | An adjective. The international standard behind the Photographic Activity Test says in its own text that the term has no clear definition and is not used in the standard | The words |
| Backing board | The rigid board behind the whole package, between the back mat and the frame's back. Not the same as the back mat the piece is attached to | Spacers, backing and the sealed package |
| Back mat (undermount) | The board the piece is actually attached to, behind the window mat | What a mat does |
| Blue Wool | A set of eight blue-dyed wool samples of known lightfastness, numbered 1 (most fugitive) to 8 (most stable), each roughly two to three times as sensitive as the next. The scale every published fade figure rests on | What the ultraviolet claim covers |
| Buffered board | Board carrying an alkaline reserve, usually calcium carbonate, that neutralizes acids as they form. Wrong for some photographic processes | Buffered or unbuffered |
| Chop, chop and join, length | Shop terms for moulding cut to size unjoined, cut and assembled, or sold by the foot | Shop terms |
| Close framing | Framed to the piece's own edge with no visible border. Legitimate, and it needs a spacer | When a mat is wrong |
| Cockling | Waves or ripples in a sheet, usually paper responding to humidity, often because it was fixed where it needed to move | What every publisher agrees on |
| Conservation framing | A shop tier, not a defined grade, in the United States. No US standards body stands behind the phrase. One trade body's board standard notes that internationally, Belgium reverses "conservation" and "museum" | The words |
| Corners (photo corners, mounting corners) | Folded paper or film pockets that hold a piece without adhesive touching it. The one mounting method a household can reliably execute | Corners and strips |
| Dose, light dose | Illuminance multiplied by time, in lux hours. Dim light for a long time does the same damage as bright light for a short time | The exposure budget |
| Dry mounting | Heat-bonding a print to a board across its whole area. A conservation institute calls it, practically speaking, irreversible | Dry mounting |
| Dust cover | Paper or spunbonded sheet across the back of the frame. Carries the dated label | Securing the package |
| Float mount | The piece shown with its own edges visible, sitting on the backing board, with the window larger than the sheet or no window at all | When a mat is wrong |
| Footcandle | An imperial unit of illuminance. One footcandle is 10.76 lux, the conservation institute's figure; two preservation centers publish approximately 11 | Lux, footcandles and the published ceilings |
| Foxing | Scattered rust-brown spots on paper. A federal leaflet on mold lists foxing among the marks mold leaves on prints and drawings | Reading the condition |
| Friable media | Media whose particles sit loose on the support: pastel, charcoal, chalk, soft graphite. They must be held further off the glazing than a four-ply mat gives | Friable media |
| Glazing | The transparent sheet at the front: glass, acrylic or laminated glass. Nothing inside the frame touches it | Glazing |
| Hinge | A small tab of Japanese paper adhering the piece to the back mat along its top edge. Deliberately weaker than the artwork, so that under duress it fails first | Hinges |
| Lignin | A component of wood that generates acid as it ages. "Lignin free" is a specification where "acid free" is not | Board grades |
| Lux | The metric unit of illuminance, one lumen per square metre. A living room in the evening is about 50 lux; average daylight is about 30,000 | What the published light figures say |
| Mat (mount, in UK usage) | The board with a window cut in it that holds the piece off the glazing and carries the mount. The UK trade calls it a mount, and calls the back mat an undermount | Mats |
| Microns | Thousandths of a millimetre, the unit the UK trade specification uses for board thickness: at least 1100 for a mount and 1500 for a backboard | Depth |
| Moulding | The profiled length the frame is made from. Its face width is what you see; its rabbet depth is what decides whether the package fits | Depth and width first |
| Museum glass, museum board | Trade names. Museum board generally means cotton board; museum glass generally means an anti-reflective ultraviolet-filtering glass. Neither is a graded specification | The four levels |
| Nominal size | The size a frame is sold at, which is also the size to cut glazing and boards to. Its rabbet measures about an eighth of an inch larger | Nominal against actual |
| Overlap | How far the window is cut inside the sheet, so the mat holds the edge down. This manual's default is an eighth of an inch per side, which is our convention and not a rule | The overlap |
| Overmat | A window mat laid over the edges of the piece. The ordinary case, which a national library says it prefers to floating | Borders and the window |
| PAT, Photographic Activity Test | An international standard test, ISO 18916, for whether an enclosure material will chemically attack a photograph. Two detectors: one for fading and spotting, one for yellowing | The one test that is a standard |
| Ply | Board thickness in trade units. Four-ply is the floor for a window mat and a back mat; this manual takes four-ply as about a sixteenth of an inch, which is derived rather than published | How deep the package is |
| Points | Flat metal tabs driven into the rabbet to hold the package in. The trade specification's top level requires points or tacks and rules out flexible tabs | Securing the package |
| Rabbet (rebate) | The step cut into the back of the moulding that holds the package. Its depth is the dimension that rules frames out | Five sizes |
| Rag board | Cotton board. "Rag" does not mean reclaimed textiles: the cotton comes from linters, the fiber left on the boll after textile cotton is removed | Board grades |
| Rotation | Taking a light-sensitive piece down for a period, so its annual exposure stays inside a published budget. The published tables give months on display per five years, with years of dark rest | Rotation |
| Sealed package | Glazing, the matted work, backing and a vapor barrier sealed into one unit and dropped into the frame. Distinct from a sealed frame, which a professional wiki advises against | The sealed package |
| Sight size | What you can see through the window: the window opening | Five sizes |
| Sink mat | A built-up frame of filler strips the thickness of the object, with a window mat over it, for anything that will not lie flat. Always overmatted | When a mat is wrong |
| Spacer | A strip that holds the glazing off the piece where there is no mat, or adds to what a mat gives. Arranged post-and-lintel so no piece can fall onto the object | Spacers |
| Stud | The vertical framing member behind a wall surface, commonly at 16 to 24 inches on center. A fixing into a stud removes most of the anchor question | Which wall is it |
| Ultimate load | The load an anchor sustained in a laboratory test. Every maker in this manual's research says to design to about a quarter of it | Hardware by published rating |
| Ultraviolet filtering | Glazing treated to block ultraviolet, usually claimed at up to 99 percent over 300 to 380 nanometres. A trade threshold allows the label at 97 percent over that band | What the ultraviolet claim covers |
| V-nail (wedge) | The wedge driven across a mitred corner from behind to hold a wood frame together. Published in sizes from 3 to 15 mm, with no maker chart mapping size to rabbet depth | Wood, metal and composite |
| Window | The hole cut in the mat. Cut smaller than the sheet, by the overlap, so the mat holds the edge down | Setting the window |
Limits
These definitions are how this manual uses the words and how the sources behind it use them. A shop may use some of them differently, which is itself worth knowing: when a term matters to a quote, ask what the shop means by it rather than assuming. Words marked as adjectives commit nobody to anything, and What "archival" means is the chapter about exactly that.