Bole (gilding ground)

Bole is a fine clay used in the coloured ground beneath gold leaf. Traditional gilding preparations combine it with glue. Related terms include bolus and poliment. Red is common, but gilding clays occur in several colours.

Between the ground and gold

The bole layer should be distinguished from gesso, the lighter ground beneath it. The Royal Collection Trust illustrates, for example, white ground, a thin yellow layer, red bole and finally gold leaf. This is a documented example rather than a universal formula for every gilded frame or piece of furniture.

The fine clay provides an even support and influences the appearance of the extremely thin gold. In water gilding, the slightly yielding underlayer also allows the gold leaf to be burnished with an agate stone. Reflective details can consequently contrast with matt areas.

Possible confusion

A red surface beneath worn gilding is not a complete material analysis. The Royal Collection Trust also describes oil gilding with coloured underlayers, but a different structure and without the same ability to burnish. Do not determine technique or age from the ground's colour alone.

Practical suggestion: Document existing wear, loose areas and previous repairs without polishing or scraping away additional layers. Clarify conservation and restoration before treatment.

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