View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by AMS Acta - Alm@DL - Università di Bologna HMC 2016 4 th Historic Mortars Conference Preliminary study on the use of ammonium phosphate for the conservation of marble-imitating gypsum-stuccoes Enrico Sassoni 1, Gabriela Graziani 2, George W. Scherer 3 and Elisa -ranzoni 4 0Tmh dqrhsxneAnknfm+)skx+
[email protected] 1Tmh dqrhsxneAnknfm+)skx+ faqhdk-fqyhmh1.tmhan-hs 2 OqhmbdsnmTmh dqrhsx+MI+TR@+ rbgdqdq.oqhmbdsnm-dct 0 Tmh dqrhsxneAnknfm+)skx+ dkhr-eqmynmh.tmhan-hs Abstract6 In this study, a novel method for consolidation and im rovement of resistance to water of gy sum-stuccoes was reliminarily investigated. The idea is treating gy sum with an aqueous solution of diammonium hydrogen hos hate (DAP, (.H 4)2HPO 4) to form hydroxya atite (HAP, Ca 10 (PO 4)6(OH) 2), which has much lower solubility than gy sum. Tests carried out on gy sum aste sam les, manufactured to resemble historic stuccoes, showed that, after treatment with the DAP solution, a significant im rovement in mechanical ro erties was achieved and brushite (CaHPO 4ì2H 2O) was formed (alongside some other by- roducts, that can be removed by an additional oultice treatment). Even if brushite is more soluble than HAP, still its formation is ex ected to be beneficial for stuccoes conservation, as brushite is significantly less soluble than gy sum. Introduction Since antiquity, gy sum-based stuccoes have been frequently used to imitate recious white or colored marbles, when the use of real marbles was not ossible, because trans ort from faraway quarries was too costly a1,2b.