Mineral consolidants

Inorganic consolidants, such as ethyl silicate, nanolime and ammonium oxalate, have proven to be effective for certain materials, but each has its drawbacks. This has recently led to the investigation of hydroxyapatite (HAP) as a novel inorganic consolidant, which demonstrated excellent performance on carbonate stones. Considering that a mineral that matched calcite crystal lattice parameters even more closely than HAP would be expected to provide a consolidating action even greater than HAP, in this study aluminum phosphate (AP) was investigated as a potential new consolidant. Indeed, AP has lattice parameters differing from those of calcite by only 1%. The consolidating ability of AP was preliminarily investigated here in comparison with HAP. Both treatments were tested on artificially weathered marble samples, in the view of their application for conservation of sugaring marble. A novel method is also proposed for producing samples with near-surface damage similar to that of sugaring marble in the field. The results of the study point out that the novel weathering method is able to provide samples with tailored gradient in dynamic elastic modulus, closely resembling naturally sugaring marble. The AP treatment was found to significantly improve the dynamic elastic modulus of weathered marble, at least as efficiently as the HAP treatment investigated in this study. This confirmed the high potential of AP as a new inorganic consolidant

Electrical microfluidic pressure gauge for elastomer microelectromechanical systems

We report on an electrical microfluidic pressure gauge. A polydimethylsiloxane microvalve closes at a characteristic applied pressure determined by the material's properties and the valve's dimensions. Hence, when the same pressure is applied to all valves of a heterogeneous valve array, some valves close while others remain open. The state of the array is combined with knowledge of the respective characteristic closing pressures of the individual valves to yield an estimate of the applied pressure. The state of each valve is obtained by electrical measurements, since the electrical resistance of the respective underlying fluid-filled channel increases by at least two orders of magnitude as the valve closes and its insulating elastomer material interrupts the electrical circuit. The overall system functions as a pressure gauge with electrical readout. This device would be a critical component in active pressure-regulation loops in future integrated microfluidic systems

Preliminary study on the use of ammonium phosphate for the conservation of marble-imitating gypsum-stuccoes

In this study, a novel method for consolidation and improvement of resistance to water of gypsum-stuccoes was preliminarily investigated. The idea is treating gypsum with an aqueous solution of diammonium hydrogen phosphate (DAP, (NH4)2HPO4) to form hydroxyapatite (HAP, Ca10(PO4)6(OH)2), which has much lower solubility than gypsum. Tests carried out on gypsum paste samples, manufactured to resemble historic stuccoes, showed that, after treatment with the DAP solution, a significant improvement in mechanical properties was achieved and brushite (CaHPO4∙2H2O) was formed (alongside some other by-products, that can be removed by an additional poultice treatment). Even if brushite is more soluble than HAP, still its formation is expected to be beneficial for stuccoes conservation, as brushite is significantly less soluble than gypsum

Consolidation of sugaring marble by hydroxyapatite: some recent developments on producing and treating decayed samples

Consolidation of sugaring marble (i.e., marble affected by granular disaggregation) still lacks fully effective solutions. Consequently, the use of an innovative phosphate-based treatment, aimed at bonding calcite grains by formation of hydroxyapatite at grain boundaries, has recently been proposed. In this paper, firstly a novel method for producing artificially decayed marble samples, by contact with a heating plate, is proposed. Then, some results are presented about the effectiveness and the compatibility of two different formulations of the phosphate treatment, differing in terms of concentration of the phosphate precursor (3.0 M or 0.1 M aqueous solutions of diammonium hydrogen phosphate, DAP), possible ethanol addition to the DAP solution and number of DAP solution applications (1 or 2). The results of the study point out that the new weathering method allows to obtain specimens with a gradient in microstructural and mechanical properties with thickness, just like naturally weathered samples. Both phosphate treatments were able to significantly improve marble cohesion, without causing significant changes in thermal behaviour and aesthetic appearance after treatment. The addition of small quantities of ethanol to the DAP solution seems to be a very promising method for favouring HAP formation and improving the treatment performance

Stone consolidation: a critical discussion of theoretical insights and field practice

Stone consolidants have been extensively used for the preservation of historical structures since the 19th century. However, their true effectiveness in practice is often a source of debate, largely because of known cases where badly chosen treatments were unsuccessful, or even caused an accelerated degradation of the substrate. Researchers have therefore strived to better understand, and possibly predict, the behavior of consolidants on-site, in order to assist practitioners in their decision making. Despite the large number of publications available on the subject, however, the contribution of scientific research for practical applications remains scarce. Reasons for this include the limited accessibility of scientific publications and the lack of documentation or preparatory studies from the field. This unfortunately compromises the knowledge exchange between researchers and practitioners, which we consider to be a main challenge that this field must overcome. The target of this letter is to reconnect the critical problems identified on-site through practical experience with the conceptual research outcomes that could help solve them. For this, we present an informed evaluation of the most needed research, along with a synthetic overview of the insights that scientific research can offer in terms of consolidant selection, application and monitoring

The Validity of Studies with Line of Business Data: Comment

In the March 1985 issue of this Review, George Benston found fault with Federal Trade Commission Line of Business (LB) data generally and singled out for extended criticism thirteen LB data-based papers written by the authors of this comment. Even by the pre-Queensberry rules governing eco- nomic disputation, Benston\u27s article is one- sided and negative. Moreover, it is marred by numerous errors in characterizing our work. We wish to set the record straight