Loose surface dirt can generally be safely removed from a gilded surface by carefully brushing with a soft-haired brush. Tate uses goat's hair brushes for this, purchased from a conservation supplier.
Ingrained surface dirt can be considered to detract from a frame's original condition. Tate conservators clean gilded surfaces using a variety of techniques, either dry or with solvent mixtures, depending on the type of gilding scheme and its general condition. Prior to any such treatment the nature of the scheme has to be understood by examination and cleaning tests.
Beyond gently dusting gilded frames, owners should seek the services of a specialist conservator to work on these often fragile surfaces which can be very quickly damaged.
Traditional gold leaf that is laid onto frames is very rarely 100% gold; in fact, to make the gold more malleable during the beating process and to improve strength and handling qualities when it is paper thin, a proportion of up to 50% of pure silver or up to 3% of pure copper is added. The addition of even tiny proportions of silver and copper can dramatically alter the appearance of the gold; silver making it lighter in colour and slightly 'colder', copper making it darker and tending towards a 'warmer' tone. Various effects can be created by using gold of different colours on the same frame.
Frames can also be decorated with metal leaf other than gold; these can be in a combination of various metals, such as copper and zinc, to create an imitation gold leaf, sometimes referred to as Dutch metal or schlagmetal, or single metals, either copper, aluminium or brass. Metal leaf (other than gold) is usually produced in sheets approximately 13 x 13 cm in size, whereas gold is produced in sheets approximately 8 x 8 cm. A worn area of a frame sometimes reveals the overlapping metal leaves and can therefore be useful in identifying the materials used.
In the case of frames that are not decorated with gold, a layer of varnish or lacquer is applied, both to prevent the surface oxidising and to give some physical protection to the surface. This lacquer layer often darkens dramatically over a long period of time. If this layer is accidentally scratched or partially removed, the underlying metal leaf will oxidise very quickly, disfiguring the surface. Real gold is often protected with a thin layer of weak parchment size, or size combined with shellac, known as ormolu. Since the oxidising components of gold leaf alloys are relatively small, this layer usually performs the task of toning down the bright nature of the new gold, and often contains small quantities of ochre or burnt umber pigment dissolved in the ormolu solution for this purpose. Very bright or burnished gold areas of a frame will have little or no additional layers applied; this is to retain the polished appearance, creating contrast with matt areas in a different part of the frame.
Firstly, look at the period/date of the frame, a pre-nineteenth century date may suggest a carved method of ornament, although frames have continued to be carved up to the present day. From the late eighteenth century English Composition started to be used as a quicker and less expensive means of recreating the effect of hand-carved ornament. English Composition (or 'compo' as it is often called) is a putty-like material pressed or rolled from metal and wooden moulds and applied to the surface of the frame for decorative effect. It can then be painted and gilded.
Secondly, look at the surface of the frame. Areas of wear and damage may well reveal the timber substrate very near to the surface, possibly indicating carving. Carved frames are sometimes 'whitened-up' prior to gilding with only a few layers, thus allowing heavy grain and knots to echo through to the gilded surface, which is all part of the frame's integrity.
Thirdly, by the nature of the constituents of composition, cracking occurs, to a greater or lesser degree, throughout the frame's life. If left untreated, the mouldings affected may eventually delaminate from the frame and leave unsightly gaps. Composition is generally a buff-grey colour, but usually was placed on a white layer. As well as composition, we see plaster and various other recipes using a plaster base being used. Plaster is more stable, but is prone to damage through impact, leaving areas which appear white. Frames are sometimes found to be made from papier-mâché, which may be indicated by the presence of fibres in any areas of damage.
February 2007
