Foxing: the small brown spots on old photographs
Foxing is scattered rust-brown dots, not a mold colony or overall yellowing. What causes it, what not to do to the print, and how it comes off a scan.
Foxing gets its name from the color, not the cause — small rust- and reddish-brown spots scattered across a print, named for a fox’s coat rather than for whatever actually put them there. It is easy to mistake for the start of a mold colony or an early stage of yellowing, and the mix-up is worth sorting out, because the three look similar at a glance but call for different handling, and only one of them is a living thing you need to worry about spreading.
What foxing actually is, and why the cause is still debated
Under a loupe, a foxing spot is a small, roughly round mark — anywhere from pinhead-sized to a few millimeters across — sitting embedded in the paper fibers rather than resting on the surface the way dust does. Spots usually appear individually or in loose, scattered clusters rather than as one connected patch, which is the most reliable visual tell: foxing is made of points, not a field. It shows up most on off-white, cream and cheaper wood-pulp papers, and it tends to concentrate near the edges of a mount or the back of a print where humidity lingers longest.
What actually produces the spot splits conservation research into two camps, and neither has fully won the argument. One explanation points to trace metal impurities — iron or copper particles introduced during papermaking or from processing water — that oxidize in place when humidity is high enough, leaving a small rust-colored stain exactly where the particle sat. The other points to fungal activity: researchers examining foxing under a microscope have found fungal spores or metabolic byproducts at the center of some spots, suggesting a form of localized microbial action too faint, or too early, to grow into the fuzzy colony people associate with mold. Which mechanism made a given spot is not something you can settle by looking at it, and conservators have not reached a consensus on which cause dominates, or whether both are often at work in the same print. What both explanations agree on is the trigger: foxing is rare on paper that has stayed consistently dry.
How to tell foxing from mold and from yellowing
| What it looks like | Where it sits | What to do | |
|---|---|---|---|
| Foxing | Small reddish-brown dots, scattered singly or in loose clusters, no texture | Embedded in the paper fibers, not sitting on top of them | Keep it dry, store it apart from other prints, scan as is |
| Mold | A colony with visible texture — fuzzy, velvety or powdery, grayish or greenish | Growing on the surface, spreading while the print stays damp | Dry the print fully first; handling needs its own care |
| Yellowing | An even, warm amber-brown cast across the whole print or a large area of it | A stain inside the gelatin or paper itself, not individual points | No physical treatment needed — a chemical stain a scan reveals |
| Water staining | Brown or yellow tide lines tracing where the water’s edge sat as it dried | Follows the outline of the spill or flood, not scattered dots | Let it dry fully and flat before scanning; do not rewet |
What not to do, and why the scan usually looks better than the print
Bleach and other whitening agents are the first thing people reach for on a rust-colored stain, and they are the wrong move here for the same reason they are wrong on a moldy print: bleach does not know the difference between the pigment that makes the spot and the pigment that makes the picture, and it attacks both. An eraser is just as unhelpful in a different way — a foxing spot is not surface dirt sitting on top of the print, it is discoloration inside the paper fibers, so rubbing at it mostly abrades the surface without lifting the stain underneath. And because both leading explanations for foxing involve moisture, wetting the spot or trying any kind of spot-cleaning adds exactly the condition that let it form in the first place.
Digitally, foxing tends to come off cleanly, and there is a specific reason for that: each spot is small and surrounded by plenty of undamaged image, which gives restoration a lot of intact detail to rebuild from — the same logic that makes a pinhole or a fine scratch an easy fix. That confidence has one honest limit. A spot that happens to land on something small and detailed — the pupil of an eye, the line of a mouth — has less nearby detail to draw on, and what fills back in there is closer to a plausible reconstruction than a recovered pixel. Most foxing spots land on skin, clothing or background rather than anything that precise, so this is the exception, but worth knowing before you look closely at the result.
Getting a foxed photo ready to scan
Keep it dry and out of direct light
A stable, moderately dry spot is the single best thing you can do for a foxed print, whichever explanation for the spots turns out to be right in this case.
Set it apart from other prints for now
Not because a spot can visibly jump from one photo to another, but because prints stored together share the same humid conditions that let foxing form — a box that produced spots on one print can do the same to its neighbors over time.
Skip any physical cleaning
Foxing is not surface dust, so brushing or wiping will not lift it, and it risks scratching the print for no benefit. Leave the spots exactly as they are.
Scan flat, the way you would any print
No special settings are needed for foxing specifically — a normal flatbed scan or a well-lit phone photo, taken straight-on, holds enough detail for the spots to be treated individually.
Let restoration remove the spots from the file, not the object
From here the work happens on the digital copy. The original print can go back into safe, dry storage exactly as it is.
Foxing and brown spot questions
What causes the small brown dots on my old photos?
Conservators point to two different mechanisms and have not settled which one explains a given print: trace metal particles in the paper that oxidize under humidity, or a faint, localized fungal reaction that never grows into a visible colony. Humidity is the common thread either way — dry storage is what keeps foxing from forming in the first place.
Are the rust colored spots on my old photo actually rust?
Not necessarily in the literal sense. “Foxing” describes the color and pattern — small rust-brown dots — rather than a confirmed cause, and while metal impurities oxidizing in the paper is one accepted explanation, a fungal origin is equally plausible for a given spot. Either way, the mark is chemical, not physical grime, so it will not wipe or scrub away.
Is foxing a type of mold?
It might share a fungal origin with mold in some cases, but it behaves nothing like an active mold colony. Mold is a living growth that spreads visibly and has real texture — fuzz, a raised surface, sometimes a smell. Foxing is flat, scattered dots with no growth to watch for, which is why it does not need the same urgent drying and isolation that active mold does.
Can foxing spread to other photos stored in the same box?
Not the way an active mold colony spreads through contact or airborne spores. Each foxing spot forms within its own print, from that print’s own paper and the humidity it has sat in. Prints stored together can each develop foxing independently if the storage conditions are damp enough for all of them — which is a reason to fix the humidity, not a sign the spots themselves are jumping from photo to photo.
Sources
- Photographic Prints — Preservation Self-Assessment Program, University of Illinois Library
See the spots lifted, not just covered
Scan the print as it is, spots and all, and upload it. Restoration rebuilds each spotted area from the picture around it in about a minute — pay only if you love the result.
Epoha is in early access: restoration is free and there is nothing to pay yet.
Sources
- Care, Handling and Storage of Photographs — Library of Congress
- How to Preserve Family Archives — U.S. National Archives