Neutron tomography for the assessment of consolidant impregnation efficiency in Portuguese glazed tiles (16th and 18th centuries)

Neutron tomography (NT) has been applied to visualize the inner structure of ancient Portuguese glazed tiles undergoing conservation treatments. Neutrons have the advantage of interacting strongly with hydrogen, so NT is able to map hydrogenous compounds with high sensitivity. The present study explores its potential for assessing the distribution of the consolidant Paraloid B-72 inside tiles, to evaluate the efficiency of two different methods of treatment: brushing and immersion in solution. Using a prototype NT setup at the Reactor Português de Investigação (Sacavém, Portugal), each two-dimensional image is obtained from a 90 s exposure, at a thermal neutron flux of 2 × 10⁵ n cm⁻² s⁻¹ at the irradiation site. The neutron beam has a diameter of 5 cm, so fragments with outer dimensions up to 4.8 cm can be inspected. Samples are automatically rotated by an angle of 0.9° between successive images. Images were obtained before and after the application of the consolidant. The results obtained show that: (i) NT is a useful tool for visualization of the inner structure of ancient glazed tiles, and to assess penetration depth of consolidant and its distribution inside the tile; and (ii) brushing with 10% Paraloid^® B-72 in acetone solution appears to be more efficient than immersion. Neutron tomography showed a greater and more uniform retention of resin inside the tile if the brush is used to apply the consolidant, to increase the cohesion of the object.     

Experimental Research with Salt Crystallization in Historical Portuguese Azulejos

The most serious form of degradation of historical azulejos is the spall of the glaze and it is widely accepted that the crystallization of salts dissolved in water circulating in the masonry is its main cause. This article reports the results of an accelerated aging test aimed at studying the physical deterioration of azulejos caused by cycles of dissolution and re-crystallization of sodium chloride (NaCl). Experiments were carried out on 26 Portuguese azulejos from the 17th–19th century, some of which with original manufacturing defects or with varying degrees of previous decay.

The results of 75 cycles over 18 months did not verify that the action of NaCl could trigger an accelerated loss of glaze in a healthy azulejo. Furthermore, the results lead to the induction that there must be other, eventually concurring, causes for the spall of glaze than a simple challenge with salts that crystallize by evaporation.     

Radical Environmentalism and “Commoning”: Synergies Between Ecosystem Regeneration and Social Governance at Tamera Ecovillage,Portugal

This article explores the scope and limitations of Radical Environmentalism as a source of practices of “commoning”. The application of the radical environmental “Healing Biotope” model in Tamera, an ecovillage located in southern Portugal, further expands the understanding of “commoning” as a social process, as well as of Radical Environmentalism as a cognitive framework. This article distinguishes between the technical and political dimensions of “commoning”. It also identifies two structuring dimensions of Radical Environmentalism, hereby called integrative rationality and the experiential action research and learning methodology. These dimensions support the technical aspect of “commoning” in Tamera by promoting epistemic and methodological coherence between social and environmental technologies. Despite their contested scientific validity, they contribute to the sustainability of the project by promoting synergies between ecological regeneration and social governance. However, they have limited capacity to address the political dimension of “commoning”, related with rank and socio‐economic inequalities among members.