Watergilding

Water gilding, or water gilding, is a traditional technique for applying gold leaf to a prepared surface using a moisture-based adhesive rather than an oil-based one. The thin sheets of gold adhere to damp size and, when burnished, can achieve a deep, glassy surface that is highly reflective. It is distinct from oil gilding, which uses an oil-based adhesive and generally yields a softer, less intense glow.

Preparation begins with a solid substrate such as wood or plaster. The surface is coated with gesso (a gypsum-and-glue mixture) and smoothed to a hard, level finish. In many practices a layer of bole (a coloured clay, often red or yellow) is applied over the gesso to add warmth to the finished gold and to improve adhesion and burnishability. The bole is sealed and sanded before gilding.

Water gilding uses a water-based size, typically prepared from animal glue dissolved in water. The size is brushed onto the bole and kept damp until ready to accept the leaf. The gold leaf, being ultra-thin, is carefully laid onto the tacky surface and patted down with a soft brush. Excess leaf is brushed away, and any wrinkles are restrained. The surface is then allowed to dry.

Finishing generally involves burnishing the leaf with a smooth agate or horn tool to enhance sheen, followed by a protective coating such as a varnish or wax. Water gilding is sensitive to moisture and abrasion, so it is usually sealed or protected when the object is in use.

Historically, water gilding has been employed for picture frames, decorative plasterwork, ceilings, furniture, and statues in Europe and parts of Asia. The technique requires precise humidity control and skilled handling, and it remains valued for the depth and warmth of its gold finish.