Terracotta Restoration: Triglav

Our Approach to Terracotta Treatments

Although terracotta is generally more robust than unfired clay, its porosity, low firing temperatures, and sensitivity to moisture make it highly vulnerable to deterioration under fluctuating environmental conditions. Conservation treatments of these kind of objects must therefore be approached addressing both structural stability and surface preservation.

Terracotta deterioration

One of the most common forms of deterioration in terracotta is mechanical damage, including cracks, chips, and losses resulting from impact, burial stress, excavation, or past handling. Terracotta tends to fracture along planes of weakness, often producing clean breaks but also generating friable edges or granular surfaces. Before any repairs can be undertaken, the fragments must be carefully cleaned to remove loose dirt, old adhesives, salts, or accretions. Cleaning is typically carried out with soft brushes, vacuum suction, and, when safe, controlled aqueous or solvent-based methods. Care must be taken, especially with archaeological pieces, not to disturb original surface coatings, slips, pigments, or burial patinas.

Environmental factors, particularly moisture and salts, present another major threat to terracotta. Because terracotta is porous, soluble salts can migrate through the body and crystallize within the pores. As these salts expand, they exert pressure that leads to flaking, exfoliation, granular disintegration, or powdering surfaces. Desalination—through repeated poulticing with deionized water or other engineered systems—may be required to stabilize the material, though the process must be carefully controlled to avoid saturating the object. Long-term preventive care includes maintaining stable relative humidity, ideally between 40% and 55%, to slow salt migration and reduce mechanical stress.

Preservation and Consolidation of Original Surface Finishes

One of the most delicate tasks in terracotta conservation is the preservation of original surface finishes, which may include slips, engobes, pigments, burnished layers, or ancient polychromy. Many terracotta sculptures and vessels were originally painted, and those pigments—often applied without a protective glaze—remain extremely fragile. Consolidation of powdering surfaces must be performed with reversible, low-viscosity adhesives that do not alter surface appearance or gloss. In some cases, facing techniques using Japanese paper may be needed to temporarily secure flaking layers during treatment.

Structural Repairs

Structural repairs typically involve the reassembly of fragments using conservation-grade adhesives. Epoxy resins were once common but are now avoided due to their yellowing, irreversibility, and overly strong bond strength. Modern conservation practice favors reversible or easily re-treatable adhesives such as Paraloid B-72, which provides a stable, controllable bond and can be adjusted mechanically or chemically in the future. Gaps and losses are often filled using inert materials such as microballoon resins, plaster, or cellulose-based fills, shaped to support the structure but toned to remain distinguishable from the original upon close inspection. Ethical reintegration avoids overfilling or visually falsifying missing areas.

Terracottas with internal voids, thin walls, or manufacturing defects may require internal stabilization. This can involve the insertion of micro-bridges, dowels, or discreet armatures to support weakened sections, particularly in large sculptures. These supports must be made from corrosion-resistant materials and designed so that they do not place stress on the surrounding terracotta.

In addition to physical and chemical challenges, many terracotta objects suffer from previous restorations that were poorly executed or have aged badly. Old fills may have become discolored, overly conspicuous, or structurally unstable. Old adhesives may have darkened, become brittle, or expanded. Removing or mitigating such materials requires patience, controlled solvent use, and sometimes mechanical reduction under magnification. The aim is always to preserve as much original material as possible while restoring legibility and stability.

Preventive Conservation.

Finally, a critical aspect of terracotta conservation is preventive conservation. Because terracotta is vulnerable to humidity, salts, and pollutants, appropriate environmental control is essential. Display and storage conditions should ensure stable humidity, minimal handling, and physical support that distributes weight evenly. Vibration during transport must be minimized, as terracotta can fracture even from low-frequency movement.