Caring for glass

Picking it up

More collections are damaged by their owners than by accidents, and almost all of it happens in the few seconds a piece is off the shelf. The habits below cost nothing and remove most of the risk.

• Both hands, supporting the weight from underneath. Take the piece at its centre of gravity rather than wherever is nearest.
• Never lift by a handle, spout, stem or rim. Those are applied parts, they are the weakest joins on the object, and a handle that has been repaired at some point can let go with no warning at all.
• Rings and watches off first. A wedding ring against a base is the commonest scratch on any collection.
• Clear the destination before you lift. Most breakages happen at the end of the journey, not the start — a piece goes down onto a surface that turns out to have something already on it.
• One piece at a time, even when that is slow, and even when they are small.
• Dry hands. A paperweight is heavier than it looks and completely smooth; a wet one is a dropped one.

Conservators generally advise against cotton gloves for glass. They are slippery, and they take away the sense of touch that tells you a piece has started to move in your hand. Clean, dry hands grip better. Close-fitting nitrile is a reasonable compromise on gilded or iridised surfaces, where fingerprints show.

Cleaning

Most glass wants dusting rather than washing. A soft brush or a clean, dry microfibre cloth will deal with ordinary household dust, and every wash is a handling event with a sink in it — so wash only when it actually needs it.

When it does: line the bowl with a towel or a rubber mat, run lukewarm water with a single drop of washing-up liquid, and do one piece at a time. Rinse in water of the same temperature, lift the surface water off with a soft cloth, and let the piece dry completely in the air before it goes back on the shelf.

• Never the dishwasher. Dishwasher detergents are extremely harsh, and the result — a permanent cloudiness with fine scratching under it — cannot be undone at home. It is the single most common way good glass is ruined.
• Never hot water into a cold piece, or cold water onto a warm one. Thermal shock cracks glass, and a piece that has been repaired is far more vulnerable to it than one that has not.
• Do not soak gilded, enamelled or cold-painted decoration, anything with a metal mount or collar, or anything with an existing crack — water gets into a crack and does not come back out.
• No ammonia-based glass sprays on iridised, gilded or painted surfaces.
• Cloudiness inside a decanter is usually not dirt. It is etching, from wine or water left standing, and it is permanent. Rice, vinegar and cleaning beads will not shift it, and used with any enthusiasm they will scratch the inside instead.

The one point at which to stop. If a piece has an oily or soapy film that returns, a fogged or milky look that will not polish off, tiny droplets on the surface, or a fine network of cracks in the skin of the glass, that is deterioration rather than dirt — sick glass and crizzling. Washing it makes it worse, because water is what drives the reaction. Keep it dry, keep it stable, and take advice from a conservator before doing anything else to it.

Display

Glass is displayed to be looked at, which usually means putting it in the lightest, warmest part of a room. That is the one instinct worth resisting.

• Out of direct sunlight. Sun through a window heats one side of a piece and not the other, and a temperature difference across the glass is exactly what a hairline crack needs. Some nineteenth-century glass was decolourised with manganese and turns a distinct purple under strong ultraviolet — a permanent change, and not a charming one on a piece you liked as it was.
• Not above a radiator, and not on the mantelpiece over a working fire. This is the classic loss, and it takes years rather than minutes, so nobody connects the two.
• Keep lamps off the object. Heat from a spotlight close to the glass dries the surface locally, which is a particular risk for anything already unstable. Distance matters more than wattage.
• Check what the shelf is standing on. Paperweights are much heavier than they look, and a run of them will bow a shelf that was fine with books. Glass shelves look right and are unforgiving of a knock.
• Leave space between pieces. Most chips happen when two objects meet, not when one meets the floor.
• Do not slide anything into place. Lift it, even two inches. A base dragged across a glass shelf picks up scratches on both.
• Museum gel under a top-heavy piece is worth it if you have a cat, a toddler or a door that slams. Test it on the base first and give it a few days before trusting it with anything you care about.

A closed cabinet solves dust, sunlight and knocks at once, and it is the single thing that most improves how a collection ages. It also has to breathe: an airtight case in a warm room will hold whatever humidity was in it on the day it was shut.

Storage

Anything not on display wants the conditions of an ordinary heated room: around 40 to 50% relative humidity, and steadier matters far more than exact. Lofts, garages, cellars and unheated outbuildings swing hard from season to season, and it is the swing that opens old repairs, blooms damp inside a box, and pushes unstable glass towards weeping.

• Acid-free tissue, not newspaper. Newsprint transfers, particularly onto anything with an open or matte surface.
• Nothing plastic against the glass. Wrap in tissue first and use bubble wrap or foam outside that; plastic held against a surface in a warm place traps moisture and can mark it.
• Do not stack, and do not let two pieces touch. Pad between anything sharing a box, and give each piece its own nest.
• Rigid boxes. A carrier bag or a soft carton offers nothing to whatever is put on top of it.
• Store stoppers out. A stopper left in a decanter can jam and then take the neck with it when someone forces it. Wrap it separately and keep it with its bottle.
• No tape on glass, ever, and no sticky labels on the base — the adhesive stays behind and can lift an original paper label with it.
• Label the box, not the object, and keep a note of what went into which one. Everybody believes they will remember.

When to stop

Nothing on this page is a repair. Cleaning, re-gluing or polishing a damaged piece at home almost always costs more value than the damage did, and it takes the decision out of the hands of whoever owns the piece next. If something is cracked, loose, flaking, weeping or simply valuable enough to make you hesitate, put it down and ask a conservator first. The pause is free.