Portrait miniatures: Common susceptibilities

by Satomi Kitano

RCA/V&A Postgraduate Conservation Programme
Specialism: Conservation of European Portrait Miniatures (MA)

Portrait miniatures were first painted in the sixteenth century. These early miniatures were painted in watercolour on vellum, usually stuck down onto a piece of playing card. The common problems associated with these miniatures are flaking paint and paint loss, which is often due to the use of thickly applied paints that contained low amounts of binding media. Blackening of lead white pigment and tarnishing of silver (which was used as a pigment) are also quite common in these periods. Eighteenth and nineteenth century miniatures are usually painted in watercolour on ivory. Ivory is susceptible to changes in humidity and can warp or crack when restrained in a tightly fitting locket. Crystal formation, flaking paint and craquelure in paint layers are also often found on ivory miniatures. All miniatures are prone to mould growth because of the micro-climate created in their lockets and frames. However, mould is particularly common with miniatures on ivory. These miniatures were often painted with watercolour containing larger quantities of gum Arabic, as a binding medium, which can be a source of food for micro-organisms.

Portrait miniature, untitled, formerly attributed to Samuel Cooper.

Portrait miniature
Untitled
Formerly attributed to Samuel Cooper
17th century
Watercolour on vellum

This image shows historical damage to the lead white paint in the face – the blackened areas are due to oxidation from pollution (red circles shows the affected areas). Micrograph x10.

Portrait miniature, Queen Elizabeth I by Nicholas Hilliard.

Portrait miniature of Queen Elizabeth I
Nicholas Hilliard
About 1586-1587
Watercolour on vellum stuck to playing card
Museum no. 23-1975

The simulated jewels in Tudor miniatures were normally created using silver as a paint. The diamonds on the sitter's hair have tarnished due to oxidation (circled). Paint loss and blackened lead white can also be seen on this miniature. Micrograph x10.

Portrait miniature, untitled, by T. C. Thompson

Portrait miniature
Untitled
T. C. Thompson
19th century
Watercolour on ivory
Museum no. P. 22-1928

Efflorescence of crystals on the paint layer. These crystals consist of magnesium phosphate, which is a natural constituent of ivory and were caused by high humidity. The miniature was already in this condition when acquired by the museum in 1928. The right hand side of this miniature has been treated using micro-crystalline wax to change the refractive index so that the crystals become less visible.

Portrait miniature, untitled, by Rosalba Giovanna Carriera

Portrait miniature
Untitled
Rosalba Giovanna Carriera
About 1710
Watercolour on ivory
Museum no. Evans.74

This is an image taken under ultra-violet light. Areas of historical retouching fluoresce differently from the original paint layer allowing us to pinpoint old losses/damage (red arrows show these areas).

Portrait miniature before conservation, untitled, by Rosalba Giovanna Carriera

Portrait miniature before conservation
Untitled
Rosalba Giovanna Carriera
About 1710
Watercolour on ivory
Museum no. Evans.74

This image shows an area of flaking paint and paint loss. This is a common problem with watercolour on ivory miniatures due to lack of adhesion between paint layer and support. This photograph shows the condition before treatment. Micrograph x20.

Portrait miniature after conservation, untitled, by Rosalba Giovanna Carriera

Portrait miniature before conservation
Untitled
Rosalba Giovanna Carriera
About 1710
Watercolour on ivory
Museum no. Evans.74

This image shows the same area of the paint layer after consolidation. Micrograph x20.

Portrait miniature before conservation, untitled, by Peter Paul Lens

Portrait miniature before conservation
Untitled
Peter Paul Lens
Mid 18th century
Watercolour on ivory
Museum no. P. 8-1934

Miniatures from mid - late eighteenth century are often painted on very thin sheets of ivory (the thickness is often less than 0.2 mm) and they are prone to warping and cracking.

Portrait miniature after conservation, untitled, by Peter Paul Lens

Portrait miniature afterconservation
Untitled
Peter Paul Lens
Mid 18th century
Watercolour on ivory
Museum no. P. 8-1934

After treatment, which included consolidation of the cracked ivory support and minor retouching to the background.

Fading due to light exposure is also a common problem with most miniatures because of their relatively thin paint layers. For this reason display light levels are controlled using visitor-operated lighting systems. Treatment options are decided with ethical consideration and carried out using appropriate conservation materials and techniques. A miniature conservator has to have knowledge of a wide variety of materials such as paints, parchment/vellum, ivory, paper, glass, metals, enamels, wood, textile and others as they are highly complex objects.