< APPLIED PATINATION PROCESSES
SURFACE CONDITION
The quality and overall condition of the cast’s surface will usually have a significant influence on a patina’s development. A cast’s surface finish is dictated in part by the textures which are transferred to the cast from the original MASTER PATTERN, and in part by machining operations carried out on the cast during the chasing and finishing stages.
When preparing models and master patterns for the art foundry, an experienced artist will be aware of the influence that texture and form has on the outcome of a patina. With this in mind, a skilled artist will manipulate the master pattern’s surface in the studio to ultimately enhance, or mute, or otherwise influence the patina later applied to the cast version.
As a general guide, cast surfaces that are smooth and flat encourage a uniform patina deposit, so any variegated effects are usually imparted deliberately by the patineur. In contrast, cast artworks with surfaces that are uneven and heavily textured tend to encourage a more spontaneous and varied patina effect. A chemical solution applied to a heavily textured surface tends to collect in undercuts and other depressions, thus depositing a heavy patina and strong colouring. On the corresponding high points of surface detail the deposited thickness patina can be comparatively light. This combined heavy and light patina deposit can have the effect of throwing textures into sharp relief, ultimately enhancing the overall effect of depth and texture across the sculpture’s surface.
The precipitated deposit of an applied chemical solution also has some effect on the visual qualities of the patina. Compounds which leave a thick and opaque surface deposit over the cast (copper nitrates and iron oxides for instance), can have a ‘flattening’ visual effect on the artwork – even if applied to a heavily textured work surface. Patination preparations that tend to deposit thin, translucent layers (ferric nitrate and potassium sulphide for instance), usually pick up underlying surface details and subtle textures with little in the way of incidental masking by the deposited compound’s precipitate.
Because a patina deposit can influence the viewer’s perception of underlying surfaces and textures, a sculptural master pattern should ideally be constructed in the studio with some idea of how the eventual patina will influence modelled surfaces. Experienced foundry personnel can normally give quite specific advice on how their various patination preparations respond to differences in cast textures and forms.
SURFACE PREPARATION >
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