Stuccatura di una lacuna

In-filling of a lacuna

The in-filling of the lacunae in the pictorial layer is the first step in the pictorial reintegration. The intervention is carried out using materials that are capable of filling and adhering to the support without greatly reducing in volume during the drying process. In addition, it is preferable that the material be easy removable and, in any case, softer than the surrounding paint layer in order to avoid damage to the original material.
The composition of the fill or putty is extremely variable, and its application must be limited to the area of the lacunae. In addition, it must be level with the surface of the painting and imitate the surface structure.


Gypsum preparation

The fill is a mixture made up of a binder and powdery or granular filler. The most traditional and usual fill is made of animal glue and gesso (but also hydrated lime, marble dust, sand etc. can be used). These materials are dissolved in different proportions in water as required. Casein, oils, waxes, resins and gums are other typical binders that have always been used in order to vary the characteristics of the mixture. Today, more modern materials can be found such as vinyl, acrylic or other synthetic polymers commercially available and ready to use. In the past, fills based on white lead were very common. The white lead was often mixed with a drying oil. Today they are no longer used because they become too rigid and are not easily reversible.

Colatura del gesso su una lacuna

Gypsum dripping on a lacuna

Before applying the fill, the restorer-conservator must verify that the original paint is perfectly stable. The damaged area must be prepared by removing dirt and residue of old fills with solvents or scalpels. (At times, the area to be filled must be treated with substances that can assist in the adhesion of the fill, such as ox gall). The fill can be applied with a spatula or dripped on using a small brush.
A spatula is most indicated for small areas filled with a wax-resin. Instead, in those areas where the lacuna is larger, it is preferable to fill slightly over the margins of the lacuna with a mixture based on gypsum and heated animal skin glue.

Levigatura del gesso

Sanding of the gypsum

Once the fill has dried, it is brought to the same level as the pictorial surface by scraping away the excess with scalpels or by rubbing with a piece of chamois skin (slightly damp), abrasive sponges or a nylon stocking wrapped around a finger. The chamois is particularly useful for removing fill residues in the proximity of the lacunae.

Imitazione della superficie

Surface imitation

The fill is then “sculpted” in order to create an imitation of the relief and the imperfections of the pictorial material that surrounds the lacuna. This can be accomplished by various methods such as impression, etching, and hatching; all using appropriate instruments. To create the sense of very unusual surfaces silicon molds can be used. The liquid fill can also be applied by using the appropriate type of syringes.
The brushstrokes of the original surface are usually imitated by trying to repeat the gesture of the artist with a brush loaded with diluted fill.

Manfredi Faldi – Claudio Paolini

ArtisEstratto da: Artis (Art and Restoration Techniques Interactive Studio), Direzione scientifica: Manfredi Faldi, Claudio Paolini. Cd Rom realizzato da un gruppo di istituti di restauro europei, con il determinante contributo della Commissione Europea nell’ambito del programma d’azione INFO2000.

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