What a hand restoration studio does that a machine cannot

There are two entirely different trades sharing one word. A photograph conservator treats the physical object: the paper, the emulsion, the mount, the damage in them. A digital restorer treats a copy, and leaves the object exactly as it was found.

Neither can do the other's job. A conservator cannot repair a photograph that has already lost its corner in 1962. We cannot flatten anything, separate anything, or reduce the acidity of a mount board.

Separating prints that have dried together, or a print bonded to its frame glass. This is done with humidity, patience and sometimes solvents, and getting it wrong destroys the print.

Flattening a rolled or badly cockled photograph, through controlled humidification and slow drying under weight.

Repairing the paper itself: filling losses with matched fibre, mending tears from the back with tissue and starch paste, stabilising a print that is flaking.

Removing a photograph from an acidic mount, or from an album page it has been glued to, which is a common and genuinely delicate job.

Surface cleaning under magnification, which is very different from wiping.

Conservation is charged by the hour, and a single treatment usually runs from a hundred to several hundred, with weeks of waiting. That is not a criticism of the price. It is one person, at a bench, with training that took years, working on your object and no one else's.

The economics only make sense per object. For one photograph that matters more than the rest — a daguerreotype, the only surviving portrait of somebody, a print with real monetary value — it is the right money. For a shoebox, the arithmetic does not work and never will.

The photograph is flaking, powdering or shedding anything at all when it moves.

It is stuck to glass, to another print, or to an album page, and you want the object itself back rather than a file.

It is a cased photograph — a daguerreotype, an ambrotype, a tintype. These are chemistry rather than paper, they tarnish, and household cleaning destroys them on contact.

It has monetary or archival value, in which case the treatment and its documentation are part of what the object is worth.

The damage is already recorded in the print — the tear happened, the fading happened — and what you want is a photograph that shows the picture rather than the damage.

There are more photographs than the budget for one. Two hundred snapshots repaired well enough to look at again beats one snapshot treated impeccably.

You want it this week, and you want the print to stay in the drawer while it happens.

You want to try it before deciding, which is the one thing a bench can never offer.

Professional conservation bodies keep public registers of accredited members, and national archives and larger museums will usually name the people they use. Local history societies and record offices know who is good regionally and will tell you.

Genealogy groups are the other reliable source. Somebody in any active society has had something treated, and they will tell you plainly whether it was worth the money.

The question worth asking on the phone is what they propose to do and what is reversible. A conservator will answer that question in detail and enjoy being asked it.