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The pastels were moved to the paper conservation studio to be treated, which provided an excellent opportunity to examine them more closely. The first task was to remove the frames and glass.

Find out more about the conservation process:

Tear repairs

The most striking damages found on these four pastels were large and visible tears to the paper support, particularly at the edges. Whilst the wooden strainer and the canvas can expand and contract with changes in environment, the blue paper is less flexible and loses strength over time, causing it to split at the corners. Additionally, the metal edge tacks had corroded through the paper, causing tears and further weakening the structure of the paper support.  

After being removed from their frames, pastels cannot be placed face down. Their delicate, powdery surfaces would be disrupted causing irreparable damage. This means they need to be treated face up or upright at all times.

These images show the conservators treating the works facing up on a flat surface, using solutions such as toned Japanese paper with a controlled amount of adhesive, and antistatic tools to avoid media offset (transfer of the powdery pastel media) and darkening. The partial repairs secured the paper support with a small amount of adhesive whilst allowing the works to move and expand with the strainer and canvas, without causing further damage.

The expansion of the strainer caused the paper to fracture resulting in an open tear at the corner. A strip of Japanese paper was toned (repair papers are sometimes painted with watercolour or acrylic paint, or dyed, to match the repair to the colour of the artwork so it blends in well) and carefully inserted beneath the tear to reduce the visibility of the facture.

The repair was lightly adhered to provide support and flexibility against any further movement. Teflon™ sheets were placed on less friable areas as an interleaving layer and the repair was left to dry with very small, light weights. Conservation methods today aim to be as non-invasive and reversible as possible, whilst being sympathetic to the original materials and the artist's intent.

Surface cleaning

Eighteenth-century pastels were intended to be framed like oil paintings, with glazing to protect the powdery surface. However, over time sealing tapes on the backboards and the expansion of the frames allow dirt and debris to make their way through crevices and gaps around the glazing. Any gaps or fractures in sealing tape or glazing makes the works more vulnerable to changes in the environment, which can cause damage to the pastel structure and the media.  

After unframing each pastel, conservators lightly surface-cleaned the verso of each artwork, first with a specialist chemical sponge and then using a piece of filter paper to gently clean in the narrow space between the canvas and strainer.

During the cleaning of the pastel of Winter the conservation team was thrilled to discover a tiny etching of the Three Kings tucked behind one of the strainer bars. Carriera is known to have placed these prints inside her pastels as a lucky charm to protect the fragile pastel from harm during transit. Examples have been found with her works in other collections, so it was very exciting to find one in one of these four pastels, hidden from view since the artist placed it there in the 1720s!

When the conservation team found it, they debated what to do with it – perhaps it should be pasted to the verso of the pastel? After extensive discussions with curators it was agreed that Carriera’s original intention should be honoured. The print was photographed and documented and then it was placed exactly where it was found.

Over time, fine surface dirt particles had deposited on the media of all four pastels. Mould growth is often encountered on pastels, as the small amount of binder present in pastel sticks does not protect the pigment. To remove the mould conservators used a brush consisting of a single hair, working painstakingly slowly under magnification. A special suction tool made up of a hair and needle was used to remove debris and mould particles without disturbing the pigment. Conservators also wore face masks to prevent disturbing any loose media by breathing over the surface.

The removal of dirt and debris on the recto (front) significantly improves the appearance of the pastel, and keeps it safe from the abrasive nature of the debris.


Over time, many of the pastel colours are prone to fading because of their characteristics and exposure to light; the pigments used are not lightfast and they usually lose their brilliance and intensity as they are not protected by a varnish or resin. This means that the appearance of pastels today, often with soft delicate tones, is not how they would have looked when they were originally made 250 years ago. The brightness of Carriera’s original colours was revealed during the conservation of the pastel of Winter. The wooden fillets tacked to the edges of the canvas were removed, revealing a bright fuchsia colour along the bottom and right edges beneath.

The fillet had protected this bright colour from light exposure. Small pigment particles offset on the fillet were sampled and then analysed at the Rijksmuseum in Amsterdam, the Netherlands. They identified the red pigment as a carmine lake pigment, which was commonly used in the making of pastel sticks. Carmine is obtained from a cultivated scale insect, the cochineal. This pigment, like many reds, is particularly prone to light fading. It is clear that Winter originally wore a bright pink wrap, with a matching ribbon in her hair.

Microclimate package and framing

Before each pastel could be put back inside its frame, a microclimate package was created to protect the work from environmental changes, dust and dirt, and to dampen vibrations that can cause dislodging of the media. This separately sealed package could be positioned safely within the newly conserved frame. The package system also makes it easier to unframe the work when need be, and gives extra protection for the work during transport. 

In order to keep the glazing away from the surface of the pastel, small tacks, pieces of cork or wooden fillets were often used to create discreet spacers. In the pastels of Spring and Autumn, small tacks are still present at each corner. The design of the conservation package incorporated these existing tacks, with a barrier made from layered mountboard to cover the tack to keep it away from the glass and preserve the original structure of the pastel.

Each pastel package was then inserted into its recently conserved and refurbished frame, with a sheet of polyester to act as a barrier and sealed with paper tape. The original, historic backboards with any labels or markings were secured with bendable plates to maintain the integrity of the object.