Restoring hundred year old objects: what is acceptable and what kills the price

Every object from this period has been treated by somebody, and the question is never whether work has been done. It is whether the work was reversible, documented and proportionate to the damage. Buyers who ask that question in the room get better prices than buyers who ask whether a piece is original. Nothing a hundred years old is original in the sense beginners mean, and a seller who claims otherwise is either careless or counting on you being careless.

The general rule is simple to state. Treatment that stops deterioration protects value, and treatment that improves appearance beyond the damage usually removes it. A consolidated flaking edge is conservation. A repainted sky is not, and the price gap between those two is enormous even when the second one photographs better.

Paintings and the traces of past treatment

An ultraviolet lamp shows retouching as dark patches against the fluorescence of old varnish, and it takes seconds to use. Look for retouching that spreads well beyond any loss, which means somebody was correcting rather than repairing. Check the back too, since a relined canvas has a second fabric attached to the original. Relining is common in pictures of this age and it matters mainly when it flattened the paint surface.

Cleaning is where irreversible harm happens most often. Removing old varnish is normal practice, but an aggressive solvent takes the thin final glazes with it, and those glazes carried much of the modelling. A picture that looks unnaturally bright and slightly flat has usually been overcleaned. That damage cannot be undone, and it should be reflected in what you pay rather than admired as freshness.

Works on paper have their own list. Washing and bleaching lighten a sheet and weaken it at the same time, and heavy bleaching leaves paper that feels papery and dead. Tape removal is delicate and often leaves a stain that no treatment clears. Dry mounting, where a sheet is heat bonded to board, is irreversible and takes a large share of value with it, so ask the question before you fall in love with the drawing.

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  Reversible treatment protects value while permanent treatment almost always reduces it
• 2
  Ask for a written condition report and any treatment records before money moves
• 3
  Use an ultraviolet lamp on paintings and on paper, since it costs almost nothing
• 4
  Stripped and refinished furniture from this period loses most of its surface value
• 5
  Polishing a chip out of glass alters the profile and shows up against a documented example
• 6
  Where a treatment cannot be described in one sentence, get it described in writing

Furniture is the category where enthusiasm does the most damage. The original finish on a cabinet is part of what buyers pay for, and stripping it back to bare wood turns a period piece into a decorative one. Waxing and cleaning are fine, and replacing missing hardware with sympathetic pieces is acceptable when it is disclosed. Sanding is not, because it removes the surface history along with the marks. Ask what a piece looked like before the dealer got it, and price the answer rather than the shine.

Deciding what to do with what you own

Get a condition report from a conservator before you commission anything, and ask specifically what would happen if you did nothing. Many stable problems are cosmetic and can be left alone for another decade without risk. When you do commission work, insist on photographs before, during and after, plus a written description of materials used. That file travels with the object and supports the price at resale.

Ask what a treatment would remove before you ask what it would improve, because only one of those is reversible.

Conservation departments at Tate and the National Gallery of Art publish accessible material on how they think about intervention. Reading a few of those explanations changes how you talk to restorers. The vocabulary alone will keep you from asking for something you cannot undo.