Flaking Gilt Rescued on a Regency Mirror Frame with Liberon Gilt Cream and Rabbit Skin Glue

The layers beneath Regency gilding

On a Regency frame from roughly 1810 to 1830, the visible gold is often 22 or 23 carat and only a few thousandths of a millimetre thick. The leaf rarely gives way by itself. The weakness usually sits lower in the build-up of the frame.

Water gilding of this period was laid over bole, commonly a red or yellow clay ground. Beneath the bole sits gesso, and beneath that either carved wood or a compo moulding pressed from hide glue and whiting. When gold comes away in curling flakes, the gesso has usually lost its grip because the animal glue inside it has become brittle with age, or because damp has made the wood swell and shrink underneath.

Before adding any material, touch a flaking area gently with a fingertip. A flake that shifts as a rigid tile usually means the whole gesso sandwich has lifted from the wood and needs consolidation from behind. If the area breaks into powder, the glue inside the gesso has failed and the missing structure has to be rebuilt.

Heating and feeding rabbit skin glue

Rabbit skin glue comes as hard granules or as a pressed cake. For lifting gesso, the usual consolidation strength is weak: about one part glue granules to twelve to fifteen parts water by volume. That is thinner than the one to eight or one to ten mix used for sizing raw wood.

Weigh the glue if you can. Guessing the ratio is the most common reason a repair pulls away again within a year. A strong mix dries hard, shrinks, and can prise up the same flake it was meant to secure.

Soak the granules in cold water for two to three hours until they swell into a jelly. Warm the container in a bain-marie, with a jar standing in a saucepan of water held between 55 and 63 degrees Celsius. A cheap kitchen thermometer is useful here.

Above about 65 degrees Celsius, the glue proteins start to degrade and the bond weakens permanently. That damage is invisible while the glue is liquid and may only show when the frame flakes again. Below 50 degrees Celsius, the glue gels before it can penetrate the gap.

Keep the water bath on a low heat and check it every ten minutes. To consolidate one lifted flake, load a fine sable brush, size 0 or 1, and feed warm glue into the edge of the gap by capillary action. Leave the surface of the gold untouched.

Lay silicone release paper over the flake and press it down with a warm, dry fingertip, or with a small tacking iron set very low. Hold the pressure for thirty to sixty seconds. The warmth keeps the glue mobile long enough to draw down, and the pressure closes the gap.

Any glue squeezed onto the gold should be lifted at once with a barely damp cotton bud. Dried animal glue on gilding leaves a shiny bloom that is far harder to remove than to prevent.

Work one flake at a time. A Regency mirror frame with egg-and-dart or acanthus moulding can have forty separate lifting sites, and each one needs the same paper-and-press cycle. The work can take several hours across an afternoon.

Materials to keep away from antique water gilding

Keep PVA, superglue, and spray fixative away from antique water gilding. They are irreversible, alter the surface sheen, and a conservator later has to remove that repair before carrying out their own work.

Animal glue remains useful because it is reversible.

Filling bare losses before colour work

Where gesso and gold have gone entirely and bare wood or compo shows through, the loss must be brought level with the surrounding surface before colour is restored. The traditional fill is gesso made from the same rabbit skin glue mixed with whiting, which is powdered chalk, to a consistency like thin single cream.

Build the fill with a brush in thin coats, letting each coat dry. A single thick fill cracks as it shrinks. Five or six coats for a chip in a moulding is normal.

Once the gesso stands slightly proud, cut it back with a damp cotton rag or a fine abrasive. Work the profile so it follows the carving on either side. A repeating moulding gives you the pattern beside the damage, so the depth of an acanthus lobe or the round of a bead can be matched by eye.

Over a bare gesso fill, brush on bole. Ready-mixed bole is sold by suppliers such as Cornelissen or Wright of Lymm, and it is commonly tinted red or yellow-ochre according to the gold tone being matched. The clay ground gives warmth beneath the later metallic colour, so a small chip does not sit as a cold grey patch inside the surrounding gold.

A filled loss without bole tends to read flat from across the room. With the fill levelled and the bole adjusted, the later Gilt Cream has depth of colour beneath it.

Using Liberon Gilt Cream on small losses

Liberon Gilt Cream is a wax-based paste carrying fine metallic powder. It is sold in small tins in shades including Chantilly, Versailles, and a range running from pale to deep gold. Its role is retouching and toning.

On a Regency frame that is 90 per cent intact, the cream is well suited to reducing the raw brightness of a new bole fill and blending a small loss into the aged gold around it. A frame that has lost half its surface needs re-leafing if the aim is to recover the depth of real water gilding across large areas.

Apply the cream sparingly with a fingertip or a cotton bud. Work it into the filled area, then feather the edge into the sound old gold. A heavy load looks like paint. Let it stand for the time given on the tin, commonly around twelve hours, then buff gently with a soft cloth to raise the metallic sheen.

Matching two-hundred-year-old gold often takes two shades. Start with the paler one, buff, then touch a trace of a deeper tone into recesses where dirt and age would naturally have darkened the original.

Colour matching against old gold is the difficult part. Regency gilding has usually oxidised and picked up grime, so it reads warmer and less brassy than fresh metallic powder. Test the mix on an offcut of gessoed board carrying the same bole before applying it to the frame. Once the cream has cured and been buffed, a thin wax over the whole frame helps the new work age at the same rate as the old.

Cleaning sound gold gently

Before retouching, the sound gold usually needs some cleaning, and this is where frames are often damaged. Water gilding is water-soluble in the most literal sense. A damp cloth can lift the gold clean off the bole.

For surface grime, use a barely moist cotton bud rolled lightly. For dust caught in carving, use a dry soft brush. For heavier deposits, conservators sometimes use saliva on a swab because it contains mild enzymes and is gentle, or they make a solvent test in an inconspicuous corner.

Household cleaners, white spirit used as a general wash, and abrasives should stay away from the surface. On oil-gilded sections, which some later Regency frames used on flat areas, the gold sits on a size and is a little more robust than water-gilt burnished passages. The difference is difficult to see by eye.

Test any cleaning approach on 1 square centimetre in a hidden spot and wait to see whether colour transfers to the swab. If it does, stop and clean dry only.

How far to clean has to be decided case by case. A frame stripped back to bright gold loses the patina that marks it as old and often looks worse than it did with two centuries of settled tone. The same darkened residue that looks like dirt under a swab can also be the depth that makes the frame read as old from across the room.