Short answer: Mat board, called mount board in British usage, is the paper-based board cut into a window and placed between artwork and glass in a frame. It frames the picture and keeps it from touching the glazing. Conservation guidance prefers cotton rag or purified, acid-free grades.
What two sources say about Mat board / mount board
| Source page | Publisher | What the page says |
|---|---|---|
| Mat (picture framing) - Wikipedia | Wikipedia | Describes a mat (mount in British usage) as a thin, flat, paper-based piece inside a picture frame. It covers fibre grades, the protective and decorative roles, and the bevelled window edge. |
| Matting and Framing for Art and Artifacts on Paper (Preservation Leaflet 4.10) | Northeast Document Conservation Center (NEDCC) | Explains the window mat as the standard mount for works on paper, cut from 100 percent cotton rag board. Its depth must keep the glazing off the artwork, and it is hinged to the backing board. |
| Matting and mounting guidance (Library of Congress Preservation) | Library of Congress | Recommends mat board of 100 percent cotton rag or purified lignin-free wood pulp, neutral or slightly alkaline, at least four plies thick. It says the object should never touch the glass, so a thick window mat or spacers are needed. |
Key points
- A mat is a thin, flat, paper-based layer inside a picture frame; mount is the British term. [1]
- It keeps the artwork from touching the glass, which avoids moisture transfer, mould and smudging. [1, 2, 3]
- Grades differ by fibre: museum board is cotton, conservation board is purified cellulose, and ordinary acid-free board is lower in the ranking. [1]
- Conservation guidance asks for 100 percent cotton rag or purified lignin-free board, neutral or slightly alkaline. [2, 3]
- The window cut-out is usually bevelled so it does not cast a shadow on the picture. [1]
- The window mat is hinged to the backing board, commonly with gummed linen tape, rather than glued to the artwork. [2, 3]
- An acid-free label alone does not guarantee long-term suitability; acidic mats can cause mat burn. [1]
Mat board / mount board compared with Backing board
| Aspect | Mat board / mount board | Backing board | Source |
|---|---|---|---|
| Position in the frame | Window mat sits in front, over the artwork. | Backing board sits behind the artwork. | [2, 3] |
| Main job | Frames the picture and holds the glazing away from it. | Supports the artwork; the object is mounted on the primary backing board. | [2, 3] |
| Typical material | Cotton rag or purified lignin-free board, at least four plies. | Cotton rag board as primary backing; acid-free lignin-free corrugated or polyolefin board behind it. | [2, 3] |
| Window opening | Cut with a window, usually bevelled. | Solid sheet with no window. | [1, 2] |
Where sources differ
Sources use mat, window mat and mount for the same item in different regions. Grade names such as museum, conservation and acid-free are not standardised across sources. Wikipedia ranks four grades; NEDCC and Library of Congress name cotton rag or purified pulp only.
Questions to ask a supplier about Mat board / mount board
- [ ] What fibre is the board made from: cotton rag, purified wood pulp or recycled pulp?
- [ ] Is the board buffered, and what is its pH?
- [ ] What is the board thickness or ply count?
- [ ] Is the core the same colour and quality as the surface paper?
- [ ] Can the supplier show a test report for the claimed archival grade?
Read next on this site
- Conservation matboard and mounting for framed prints: what the museum guidance says
- Conservation Mat Board Specs from Four Bodies (Data)
- What lignin-free and alpha-cellulose mean in matboard
More terms and explainers
Start an enquiry when your list is ready; we reply within 1 business day.
Sources: [1] Wikipedia, fetched 2026-11-12; [2] Northeast Document Conservation Center (NEDCC), fetched 2026-11-12; [3] Library of Congress, fetched 2026-11-12. As of 2026-11-12. General information, not legal, customs or tax advice. Wording is paraphrased from the pages linked; your written quote and contract govern.