Stabilisation Treatments with Aerosols: Evaluating the Penetration Behaviour of Gelatine and Methylcellulose

Abstract

In the stabilisation of unbound paint layers on paper and fragile papers with misted adhesive solutions, the distribution of the consolidant determines whether the stabilisation treatment is effective. Knowing the distribution of the adhesive throughout the pigment-paper matrix is therefore crucial. It was studied by labelling gelatine and methylcellulose solutions with fluorescent dyes. Their distribution was analysed in thin sections by fluorescence microscopy. The penetration of the misted 0.25-1% adhesive solutions into powdery pigment layers was investigated by simulating gouaches and pastels with a low ratio of binding agent vs. pigment. The penetration of these dilute adhesives into paper substrates was evaluated using four types of paper with different porosities. The following application techniques were compared: repeated applications with and without intermediate drying, applying the aerosol on the suction table and adding alcohol to the consolidant to decrease its surface tension. The results show that the distribution of misted adhesives is governed by the method of application. Drying between applications diminished the penetration of a 1% gelatine solution. The penetration behaviour of the misted adhesives was influenced by the water absorbency of the paper. Porous papers are completely saturated by 0.5% gelatine solutions. On samples with a low porosity, the adhesive was deposited mainly at the surface. Immersing the papers in 0.5% solutions of gelatine or methylcellulose always led to a full penetration of the paper with the adhesive, regardless of the water absorbency of the paper. Aerosol misting allowed a highly localized precise application, making it a suitable method for local stabilisation of media and paper.

Innovation in Green Materials for the Non-Contact Stabilization of Sensitive Works of Art: Preliminary Assessment and the First Application of Ultra-Low Viscosity Hydroxypropyl Methylcellulose (HPMC) by Ultrasonic Misting to Consolidate Unstable Porous and Powdery Media

“…Two challenging consolidation treatments were successfully carried out at the Munch Museum and the V&A Museum by misting novel, ultra-low viscosity HPMC-based solutions. In contrast with traditional consolidation media, such as Isinglass or A4C, the ULV-HPMC materials can be nebulized at considerably higher concentrations [49] The new approach, using green ultra-low viscosity materials, allows one to limit the exposure to water and reduce the risks related to repeated applications. The peel test suggests the desirable adhesive and cohesive properties of the ULV-HPMC material, and The new approach was taken using ultra-low viscosity MOBS 3P4.…”

“…While the increase of consolidant concentration from 0.1-0.25 wt% (traditional misting treatments using A4C) to 3.5 wt% (Edvard Munch treatment) or to 6 wt% (top MOBS 6P4 concentration using AGS-2000) may appear a small improvement, the major breakthrough is that the paint could be stabilized in 1-2 misting applications instead of 10 or more repeated applications, which typically are required when using high viscosity materials [10,13,14,49]. The decrease of water exposure could reach 400-900% (1-2 applications vs. 10), which is can be considered a significant improvement when treating water-sensitive surfaces.…”

Colour Stability of Natural Adhesives – Light Ageing of Adhesive Films and Colour Changes of Pigment Layers after Aerosol Application

“…Soaking or flooding of the samples with consolidation medium resulted in more changes of ΔE* ab -values than a multilayered application. However, Hummert et al (2013) studied the penetration behaviour of consolidants and showed that a single application leads to a more even distribution of the consolidant than a multilayered application. This is also dependent on the thickness of the pigment layer and should be kept in mind.…”

The case of Capogrossi in Rome: criteria and limits in the retouching process of a contemporary mural painting

“…One more natural polymer, recently re-discovered in the field of conservation, is hydrolized collagen protein or gelatine. Old and recent studies showed that this material can be a good consolidant, a good adhesive and could probably be used for pictorial reintegration too (Abrusci et al 2004;Hummert et al 2013;Azolini et al 2019).…”