TL;DR — A mat — the card border between a print and its frame — does more than fill space: it gives the image room to breathe, protects the paper, and makes a modest print look considered. The reliable choices are an acid-free board in a neutral off-white, a generous margin (often wider at the bottom), and a single or double mat that echoes the artwork. This guide explains each decision.
By Found Poster · Published September 2026
What a mat is for
A mat serves three purposes at once. Visually, it gives the artwork breathing space so the eye settles on the image rather than the frame. Practically, it holds the paper off the glass — essential in humid rooms, where a print pressed against glass can stick or foxing can form. And archivally, an acid-free mat protects the edges of the paper from the browning that ordinary card causes over time. A good mat is decoration, spacer and conservation in one.
Margins: how wide, and why bottom-weighting
A generous margin almost always looks better than a skimpy one; a narrow mat can make a print feel cramped. For most posters a border of 2 to 3 inches suits a mid-size frame, more for a large one.
Traditionally the bottom margin is cut slightly deeper than the top and sides — ‘bottom-weighting.’ It corrects an optical illusion: with equal margins, a framed image appears to sit slightly low. A little extra at the bottom makes it look centred.
Colour: neutral almost always wins
For vintage posters, a neutral off-white or warm cream mat is the safe, correct choice: it flatters the aged palette of the artwork without competing. Bright white can look harsh against warm-toned lithographs; strong colours date quickly and fight the image. If you want a little depth, a double mat — a thin inner band of a colour drawn from the poster around a neutral outer — adds refinement without shouting.
Materials and cutting
Ask for acid-free (conservation or museum) mat board; it is the same principle as acid-free paper, and it prevents the mat itself from staining the print. A clean bevelled cut on the window edge is the mark of good framing. If you are matting a set to hang together, keep the mat colour and margin identical across all of them — consistency is what turns several framed prints into a collection.
A good mat lifts an inexpensive print; every file in the archive is built to reward careful framing. Browse the archive →
Frequently asked questions
How wide should the mat be?
Usually 2 to 3 inches for a mid-size frame, more for a large one — a generous margin looks more considered than a narrow one.
What colour mat is best for a vintage poster?
A neutral off-white or warm cream, which flatters the aged palette without competing. Avoid harsh bright white and strong colours.
Why is the bottom margin often deeper?
‘Bottom-weighting’ corrects an optical illusion: with equal margins a framed image looks slightly low, so a little extra at the bottom makes it appear centred.
Does the mat need to be acid-free?
Yes — like acid-free paper, it stops the board browning the edges of the print over time and keeps the paper off the glass.
Further reading
- Framing posters without glare
- How to print and frame a vintage poster
- AIC (American Institute for Conservation), guidance on matting works on paper
Found Poster restores Belle Époque and Art Nouveau posters from museum archives into archival-quality files you print yourself. Browse the archive · How to print & frame.
