Conservation matboard and mounting for framed prints: what the museum guidance says

Framing guidance from libraries and conservation bodies covers mat, backing, mounting and glazing materials [1][2][3][4]. For the mat, the Library of Congress asks for 100% cotton rag or chemically purified, lignin-free wood pulp stock, pH-neutral or slightly alkaline (pH 8.5), and 4-ply minimum [1]. Fibre, lignin, pH and ply are useful checks when you compare a framed print from one supplier with another.

Much of this guidance is written for works on paper. The Library of Congress says its guidelines can apply to reproductions [1].

Two fibre sources appear in the guidance: cotton rag and purified wood pulp. NEDCC advises 100% cotton rag board for window mats and the primary backing board [2]. CCI says manufacturers describe conservation matboard as 100% rag fibre, and treats highly purified wood pulp buffered to pH 8.5 as a cheaper acceptable option [3]. CCAHA asks that board be free of lignin, ground wood and metallic particles [4].

NEDCC lists lignin-containing paper-based mat boards among materials to avoid [2]. The sources opened here do not explain the chemistry, so this guide does not either. For the terms in detail, see lignin and alpha-cellulose in matboard.

NEDCC says most mat boards are buffered with an alkaline material such as calcium carbonate, and that unbuffered boards are available for sensitive photographic materials such as cyanotypes [2]. CCI says buffered matboard is designed to protect paper from acidity and suits most works on paper [3]. CCAHA says the calcium carbonate buffers against acid migration and oxidation over time, and that cyanotypes should be matted with neutral pH board [4].

The Library of Congress asks that board used for matting photographs pass the Photographic Activity Test (PAT) [1].

The figures differ between bodies. CCI gives pH 7.5 to 8.5 for buffered matboard and pH 7 for unbuffered matboard [3]. CCAHA mentions boards buffered with 3.5% calcium carbonate [4], and one museum manual lists a lignin-free library board buffered with 3% calcium carbonate to pH 8 [5].

The guidance states board thickness in ply, and it clusters around 4-ply. The Library of Congress names 4-ply as a minimum and CCI recommends 4-ply matboard [1][3]. NEDCC says four-ply can work, but thicker mats are required for large sheets [2]. CCAHA says most flat paper items should be matted with 8-ply or 4-ply boards [4].

CCAHA says distorted, thick-media or very large items may need extra depth between the artwork and the glazing, for example from acrylic spacers wrapped with alkaline paper or additional layers of ragboard [4].

For the back, the Library of Congress asks for a backing board at least 3 mm thick [1]. Millimetre thickness for the mat itself is not given in the sources opened, so this guide does not convert ply into millimetres.

The Library of Congress says overmatting provides more protection than floating the object in the window [1]. For the comparison in detail, see overmat versus floating mount.

CCI says windows are typically cut at a 45 degree bevel, with the mat covering the artwork edges by at least 2 mm to 4 mm, top and side margins usually equal and the bottom margin slightly wider [3]. The front and back boards are joined along one edge with gummed linen tape [3]. NEDCC says the mat and backing board should fit the frame with 1/16 to 1/8 inch of total play [2].

CCI calls hinging the best way to attach works on paper to their mats [3]. The detail sits in hinges, corners and adhesives for mounting a print; in short:

• Hinges: NEDCC describes Japanese paper hinges adhered with wheat starch paste [2]. CCI says most works on paper need two hinges, and larger objects may need more [3]. CCAHA says hinges go five inches apart [4].
• Non-adhesive options: the Library of Congress prefers non-adhesive hinging, such as photo or mounting corners, polyethylene strapping or mounting strips, whenever possible [1].
• Where it attaches: NEDCC says the object must be mounted on the primary backing board and never on the reverse of the window [2].

To avoid: NEDCC names non-archival or self-adhesive tapes and adhesive transfer gum [2], and CCI says gummed and pressure-sensitive tapes are discouraged [3]. This guide does not cover dry mounting; ask your framer how the print is attached and whether it can be reversed.

The print size and the 50 mm margin below are invented (illustrative) to show the arithmetic. The 2 mm to 4 mm overlap comes from CCI [3].

Take a print measuring 300 mm wide by 400 mm high that you want overmatted. CCI says the mat edges should cover the artwork edges by at least 2 mm to 4 mm [3]. The overlap applies on each side, so the window is smaller than the print by twice the overlap in each direction. Because CCI's wording is a minimum, a larger overlap gives a smaller window.

• Window width: 300 mm minus 2 x 2 mm = 296 mm for a 2 mm overlap, and 300 mm minus 2 x 4 mm = 292 mm for a 4 mm overlap.
• Window height: 400 mm minus 2 x 2 mm = 396 mm for a 2 mm overlap, and 400 mm minus 2 x 4 mm = 392 mm for a 4 mm overlap.

Now consider a wider margin. If you choose a 50 mm margin on each side of the window (an invented figure, for arithmetic only), the board width is the window width plus 100 mm: 296 + 100 = 396 mm for the 2 mm overlap, or 292 + 100 = 392 mm for the 4 mm overlap. The height works the same way: 396 + 100 = 496 mm, or 392 + 100 = 492 mm, before any wider bottom margin, which CCI describes as usual [3]. NEDCC says thicker mats are required for large sheets [2]; the sources opened do not define how large.

The Library of Congress recommends UV-opaque acrylic, also available as anti-static for objects with friable media, and says to keep the object from touching the glazing by using a sufficiently thick-ply window mat or adding spacers along the perimeter of the mat [1]. NEDCC says glazing should filter at least 99 percent of UV, and that conventional acrylic must never be used for objects with friable media [2]. For a comparison of the two materials, see acrylic versus glass glazing.

The Library of Congress says a wooden rabbet should be lined with a barrier film, and NEDCC says a rabbet may be lined with a barrier material such as polyester film [1][2]. NEDCC also describes an archival paper or Tyvek dust cover on the back of a permanently housed frame [2]. For mouldings, see frame materials compared and frame profiles.

Depth is covered too. The Library of Congress says the frame must be of sufficient depth to accommodate the complete package including the backing board [1]. CCAHA says the frame should be deep enough to accommodate the glazing, matted artifact and backing board without extreme pressure [4]. A thick mat stack therefore takes up part of that depth (an inference from [1] and [4]).

Ask the board maker to state each of the following in writing, rather than relying on a grade name.

1. Fibre and lignin: 100% cotton rag, or chemically purified, lignin-free wood pulp [1][2][4].
2. Buffering: buffered, or unbuffered where the print process needs it [2][3][4].
3. pH: the figure the board maker publishes. The sources quote pH 7 to 8.5 depending on board type [1][3].
4. Ply: 4-ply (Library of Congress minimum), thicker for large sheets [1][2][3].
5. Mounting: hinges [2][3] or non-adhesive supports [1], attached to the backing board [2], with no self-adhesive tape [2] and no gummed or pressure-sensitive tape [3].
6. PAT: a pass for the board if the pieces are photographs [1].

Marketing words such as "museum quality" are not defined in the sources opened for this guide, so ask for the technical data sheet and compare it with the list. For how to write the rest of a brief, see how to brief a frame or board order. Order a paid sample and check the mat edge, the hinge or corner method and the glazing gap before you commit to a bulk run.

ArtzFolio is a private-label and OEM/ODM manufacturer in Noida, serving businesses and brands only, and we make photo frames and wall art among other lines. Put any mat specification in your brief; minimums, lead time and price are confirmed in the quote. Samples are paid, and the cost may be reimbursed or adjusted by agreement. Payment is 50% advance, with the balance as agreed, and our shipping term is EXW Noida. We aim to reply within 1 business day. See pricing, minimums and lead times or contact us.

1. Preservation: Matting and Framing, Library of Congress. loc.gov (read 2026-11-08)
2. 4.10 Matting and Framing for Art and Artifacts on Paper (Preservation Leaflet), Northeast Document Conservation Center (NEDCC). nedcc.org (read 2026-11-08)
3. Matting Works on Paper (CCI Notes 11/5), Canadian Conservation Institute, Government of Canada. canada.ca (read 2026-11-08)
4. Matting and Framing Specifications for Objects on Paper, Conservation Center for Art and Historic Artifacts (CCAHA). ccaha.org (read 2026-11-08)
5. Appendix 6: Packing, Storage and Mounting Materials, Western Australian Museum (collection manual). manual.museum.wa.gov.au (read 2026-11-08)