The most expensive mistakes in this trade are rarely made by people who call a conservator too often. They are made by people who look at a genuinely serious problem, decide it looks manageable, and reach for a tube of glue instead of the phone. Damage to antiques has a way of hiding its true severity — a hairline crack in porcelain can look cosmetic and actually run through a structurally critical area; a small area of active woodworm can look contained and actually indicate a colony well established throughout a piece’s frame. Learning to recognize the signs that separate a minor, safe-to-attempt problem from a serious one is arguably more valuable to a collector than learning any specific repair technique, because it is the judgment that determines whether a repair technique should even be attempted.

Structural Compromise: When the Piece Can No Longer Bear Its Own Weight

Any sign that a piece is no longer structurally sound on its own terms is an immediate professional-conservator situation, full stop. This includes:

  • Furniture joints that have failed to the point that the piece visibly racks, wobbles severely, or cannot bear normal weight
  • Cracks in ceramics or glass that run through structurally load-bearing areas — the base of a vessel, the neck of a vase, the point where a handle joins a body
  • Splits in wood panels or veneer substrates that have progressed beyond surface checking into full separation
  • Any repair from a previous restoration that has itself failed, since this usually means the underlying problem was never properly addressed the first time

The reasoning here is straightforward: a structural failure that is patched rather than properly repaired does not stay static. It tends to progress, often worse and faster once the compensating stress finds a new point of weakness, and a home fix applied under time pressure or without the right clamping and support tends to lock a piece into a slightly wrong alignment that a professional then has to undo before they can even begin the real repair.

Structural damage rarely announces itself as an emergency. It shows up as a slight wobble, a hairline crack, a joint that’s “just a little loose” — and it is precisely that quiet presentation that leads people to underestimate it.

Active Pest Infestation

Live woodworm, active clothes moth or carpet beetle infestation in textiles, or any other active pest problem is a professional matter, not a DIY one, and the reason is about scope rather than technique difficulty. Effective pest treatment requires accurately identifying the specific pest and its life-cycle stage, correctly assessing how far an infestation has spread (often well beyond the visibly affected piece, into surrounding furniture or storage), and choosing a treatment — freezing, controlled anoxic environments, or in some cases professional fumigation — appropriate to the material involved and the extent of the problem.

Signs of an active infestation worth treating as urgent:

  • Fresh, pale wood dust (“frass”) beneath a piece of furniture, distinct from old, dry, darkened frass which may indicate a dormant or historic infestation
  • New, clean-edged exit holes in wood, as opposed to old, weathered holes
  • Visible larvae, adult insects, or shed casings in or near textiles
  • A faint but distinct musty or unusual odor associated with an affected area
  • Irregular grazing or hole damage appearing or spreading on a textile over a period of weeks

A DIY pesticide treatment applied to the wrong pest, at the wrong life stage, or without addressing the full extent of an infestation frequently fails to actually solve the problem while introducing chemical residue that complicates future conservation work.

Active Mold or Water Damage

Mold growth on any antique material is both a conservation emergency and, depending on the species and extent, a potential health concern for anyone handling the piece, which pushes it firmly into professional territory. The urgency is real: mold can spread across a textile, a book, or a painting’s surface within days under the right humidity conditions, and once mold has been actively growing, it typically leaves behind both structural weakening of the affected fiber or material and staining that ranges from difficult to impossible to fully remove.

Water damage more broadly — a flooded basement that reached stored furniture, a burst pipe near a cabinet, a leak that soaked a textile — deserves the same urgency even before visible mold appears, since damp organic material can develop mold within 24 to 48 hours in warm conditions. A piece that has been wet should be assessed by a professional promptly, ideally before it has fully dried in an uncontrolled way, since improper drying (too fast, with heat, or in direct sun) can cause warping, splitting, and further finish damage on top of whatever the water itself already caused.

Metal Corrosion Beyond Surface Tarnish

Ordinary tarnish on silver is cosmetic and safe to address with conservative home polishing. Active corrosion is a different phenomenon entirely and a clear signal to call a metals conservator:

  • Bronze disease — a bright green, powdery corrosion on bronze or copper-alloy objects, distinct from the stable, even dark-green patina considered desirable on aged bronze — is an active, self-propagating chemical process that will continue to consume the metal if untreated and can spread to other bronze objects stored nearby.
  • Pitting corrosion on silver or other metals that has progressed past the surface into visible material loss.
  • Any corrosion on iron or steel components that is actively flaking or expanding, since iron corrosion products take up more volume than the original metal and can physically crack surrounding material as they expand.

Previous Repairs Using the Wrong Materials

A surprisingly common reason serious collectors end up in a conservator’s workshop is not new damage at all — it is old, amateur repair work coming due. Cyanoacrylate (“super glue”) on ceramics yellows and becomes brittle within a few years and is notoriously difficult to remove without solvents that risk the surrounding glaze. Epoxy used on furniture joints creates a bond stronger than the surrounding wood, meaning any future stress at that joint tends to tear out original material rather than simply releasing, the opposite of how a well-executed traditional repair behaves. Household paint or varnish applied over an original finish, intended as a quick cosmetic fix, frequently proves far harder to remove than the finish it was meant to improve.

If a piece coming into a collection shows signs of prior amateur repair — an obviously mismatched glue line, a slightly too-glossy patch of finish, hardware that doesn’t quite match its surroundings — that is itself a signal worth taking to a professional, both to assess what was actually done and to determine whether it can be safely reversed or needs to be worked around.

A Practical Red-Flag Checklist

Any one of the following is a reasonable trigger to stop, put the piece down, and call a professional rather than attempting further home intervention:

  1. The piece cannot bear its own normal structural load.
  2. There is a crack or split in a load-bearing area of ceramic, glass, or wood.
  3. There are signs of active, live pest infestation.
  4. There is visible mold growth or the piece has been recently and significantly wet.
  5. Metal shows active, spreading corrosion rather than stable surface tarnish.
  6. A previous repair is failing or was clearly done with inappropriate materials.
  7. The piece has meaningful monetary, historical, or sentimental value and you are not confident the intended repair is fully reversible.

Why the Call Is Worth Making Even When Uncertain

The cost asymmetry here strongly favors caution. A consultation with a conservator to assess a piece that turns out to be fine costs relatively little — often just the time of a short evaluation. A well-intentioned but wrong home repair on a piece with a genuinely serious underlying problem can convert a fixable issue into one that is expensive, sometimes permanently compromised, and occasionally simply unrepairable. Conservators see this pattern often enough that most would rather field a call about a problem that turns out to be minor than be handed a piece after a home repair has already gone wrong.

A conservator’s honest advice, given early, is nearly always cheaper than the same conservator’s honest advice, given after the damage has already been made worse.

The collectors who protect their investment best are not the ones who never attempt anything themselves. They are the ones who have learned to recognize, quickly and reliably, the handful of warning signs that mean a piece has moved out of DIY territory — and who act on that recognition before curiosity or economy tempts them to proceed anyway.