Workshop on the Heat and Low-Pressure Table in the Conservation Studio

The conservation studio of The Phoebus Foundation has recently acquired a new addition: a heat and low-pressure table. This significantly expands the range of possibilities within conservation projects, while supporting an approach based on minimal intervention and maximum control.

Heat and low-pressure table in The Phoebus Foundation’s conservation studio, used for controlled conservation treatments with minimal intervention.

As the conservation team is constantly working on a wide range of treatments, the heat and low-pressure table can play a meaningful role. To explore its use and potential with due care, a workshop was organised, giving conservators insight into its operation, applications, advantages, and points of attention, with a view to its thoughtful use in practice.

For this occasion, Davide Riggiardi travelled from Italy to the conservation studio of The Phoebus Foundation for a three-day workshop, where he shared his expertise on the applications and possibilities of the heat and low-pressure table.

Professor Riggiardi teaches paintings conservation at the Academy of Fine Arts of Palermo and contemporary art conservation at the Academy of Fine Arts of Brera. He is also active as a conservator in his own studio in Milan, where he focuses on preventive conservation and minimal intervention.

Workshop in The Phoebus Foundation’s conservation studio, where participants gather around a table for a theoretical introduction to conservation techniques, with a projection of a heat and low-pressure table in the background. — The workshop opened with a theoretical introduction by Professor Davide Riggiardi

The principle behind the table lies in its perforated surface, which allows air to be distributed evenly. When a painting is placed on the table and covered with a layer of Melinex (polyester film), a vacuum pump draws the air out from beneath the object, creating low pressure. The painting is gently pulled downwards, resulting in an even tension across the entire surface, without applying direct pressure to the paint layer. Unlike the use of weights, the intervention remains highly controlled and exceptionally subtle.

Hands-on exercises during a conservation workshop at The Phoebus Foundation, where paper mock-ups with powdery paint layers are consolidated with and without a low-pressure table, using different adhesives and application techniques.

One of the practical sessions involved comparing consolidations carried out on mock-ups, both with and without the use of the low-pressure table. Both mock-ups were distorted and showed the same powdering paint flakes. Seven different adhesives were applied to the surface in various ways: using a brush, a tissue and a spray gun.

Initial observations showed that, in consolidations carried out on the low-pressure table, the solvent evaporated more quickly and penetrated the layers more deeply and evenly. Without low pressure, by contrast, ring formation and distortion occurred, indicating an uneven distribution of adhesive and a less effective consolidation in depth.

Edge lining of a canvas during a conservation workshop at The Phoebus Foundation, carried out on a heat and low-pressure table to allow controlled drying, reduce tension, and precisely apply thermoplastic adhesives.

In addition to consolidation, the workshop also addressed the execution of edge linings on the heat and low-pressure table. This relatively minimal and, depending on the adhesive used, reversible intervention reinforces weakened canvas edges and enables re-stretching, while the low-pressure function allows for controlled drying without weights and avoids direct pressure on the paint layer. By increasing the temperature, thermoplastic adhesives can also be applied.

The conservators experimented with various adhesives, including Plextol© and BEVA® 371, as well as with different application techniques. The various functions of the table were also tested during the execution of edge linings, both under low pressure and at elevated temperature.

Detail views of edge lining during a conservation workshop at The Phoebus Foundation, where thickened Plextol® is applied with a mesh screen onto canvas to achieve an even, strong bond under controlled pressure and temperature.

Applying thickened Plextol© using a mosquito net results in a chequerboard pattern. This even distribution ensures stronger and more uniform adhesion between the original canvas and the edge lining.

Application and positioning of an edge lining on the reverse of a painting during a conservation workshop at The Phoebus Foundation, followed by controlled drying under low pressure to minimise impact on the paint layer.

The edge lining is first positioned on the reverse of the painting. The painting is then turned over and placed under low pressure to dry in a controlled manner. The pressure is generated beneath the painting, while the pictorial layer remains as undisturbed as possible.

Conservators and participants gathered around paintings on easels, holding a joint discussion and evaluation of conservation treatments.

These examples represent only a small selection of the applications of the heat and low-pressure table. An entire day was devoted to discussing various case studies drawn from conservation treatments currently underway in The Phoebus Foundation’s conservation studio. The conservators exchanged views with one another and with Professor Davide Riggiardi on questions relating to challenging consolidations and the treatment of supports. Many ideas emerged from these discussions, some of which will soon be put into practice with the greatest possible care for the artworks.