WOOD
Wood has always been the main material for the realization of objects or products, from furnishing to structural elements production. Natural and valuable, it requires special care to maintain its aesthetics and mechanical properties. The problem of preservation and restoration of wood – more simply, of restoration – is a modern concept, though in the past the problem of endurance was dealt with by using techniques that, even if empirical, are still applied and valid to date. As an example, in “De re aedificatoria” Leon Battista Alberti recommends various remedies to prevent ageing and deterioration of wood, among which the use of oil deposit against woodworms or the application of Greek tar to prevent moisture. In order to understand the behavior of wooden structures, the nature of this material itself has to be taken into consideration. Water is a key factor for the preservation of wood; being a component of wood itself, water is at the same time the recurrent cause of its deterioration. Moreover, this material’s high hygroscopicity can cause remarkable dimensional modifications, which are not homogeneous due to its anisotropy. The modern approach to wood restoration and consolidation is based both on scientific grounds – products for wood restoration are part of this branch – and on the restorer’s skills. In any case, protection from moisture and woodworms – wood’s major enemies – as well as from fire remain the major issues. The PHASE wood line offers a wide selection of products for sanitisation, consolidation and protection treatments, easy to apply and very effective.
Historical overview
Wood has been one of the first building materials used by man thanks to its availability in nature and its properties of resistance, workability and versatility which favoured wood’s extensive use in the realization of structures and various other type of works (architraves, slabs, trusses, assembled beams, sculptures, furniture). As for artefacts, wood has been subject to changing luck over the centuries and, after being widely used in ancient times – painting on wood panels was common in Egypt already in the 13th and 12th centuries B.C., while in the Middle Ages wood was used for panel painting and wooden sculpture –, was progressively replaced by painting on canvas as well as stone and metal sculpture.
Compared to these materials, wood properties make it necessary to apply a polychrome layer as finishing of the artefacts. Most frequently, the limited dimensions of the tree trunks require several number of pieces to be prepared individually, then assembled together with joints which are difficult to hide. In addition, the very same nature of wood with its veining, knots and color variations interferes with the representation if the artwork is not painted. In the same way, its structure of parallel fiber bundles imposes a type of manufacturing that cannot mimic the nature of the material. The problem of polychrome coating is one of the crucial issues in the historical-critical and preservation debate on wood and stone sculpture: without doubt, most of the ancient sculptures and architectures were vividly polychrome, but the neoclassical theories introduced the habit of considering such artworks as monochrome. Until the first decades of the Twentieth century and beyond, their restoration, dependant on the aesthetic concept, the place and the worker of the time, often resulted in the destruction of polychrome traces, due to the modern aesthetic taste which fostered unrefined materials. This attitude also influenced the restoration of wooden artefacts: lacunae of painting layers on a wooden sculpture do not entail the total loss of a part of the artwork and may be more easily and extensively reintegrated than lacunae on wooden panel paintings. The most common essences used in fine arts in Europe and Italy are the broadleaf trees:
- Poplar: one of the most commonly used species, being it easy to find and work, although non-resistant and non-durable, and easily subject to xilofagus insect attacks. Lime is extensively used in wooden sculpture. Compared to poplar, its fibers are more compact but easy to work, and is also subject to xilofagus attacks.
- Walnut: mainly used for panel paintings of small dimensions, it is compact and resistant although subject to xilofagus attacks.
- Oak: employed in all its varieties, it is strong and resistant, extensively used for panel painting and furniture manufacturing. It is resistant to xilofagus attacks although, shrinking highly when aging, it is not suitable for wood sculpture.
Wood essences from fruit-bearing trees were not used as supports for panel painting but were extensively employed for woodcut-blocks and small sculptures due to their optimal hardness and compactness. Among conifers, the most widely used for panel paintings was the European silver fir, easily attackable by xilofagus insects. Less used is the Norway spruce, more compact than silver fir. Larch has a good durability, regular and very compact fibers, and is anyway easy to work. Other species such as pine, cypress, cedar were used less frequently, despite having a good resistance to xilofagus attacks, but being less easily-processed. Usually, the selection of wood was entrusted to the artist, according to the rules stated by his corporation. The most suitable species for carving are those with a compact structure, regular veining and medium hardness, though actually all types of locally available and handed-down-by-tradition timbers were used. Unseasoned empty trunks, then dried prior to the application of the polychrome coating, were used for wood sculpture. Fully seasoned timber, sometimes “cooked” in boiling water to limit dimensional variations when drying, was used for artworks of small dimensions, panel painting and decorative elements. Once the wooden support completed, pieces of canvas or parchment paper were applied on junctions or cracks to absorb wood movements on the finishing layer, which was applied by the same engraver or entrusted to a different artist.
