title: Early stage of weathering of medieval-like potash-lime model glass: evaluation of key factors.
abstract: OBJECTIVE
  Throughout history, a consequent part of the medieval stained glass windows have been lost, mostly because of deliberate or accidental mechanic destruction during war or revolution, but, in some cases, did not withstand the test of time simply because of their low durability. Indeed, the glasses that remain nowadays are for many in a poor state of conservation and are heavily deteriorated. Under general exposure conditions, stained glass windows undergo different kinds of weathering processes that modify their optical properties, chemistry, and structure: congruent dissolution, leaching, and particle deposition (the combination of those two leading together to the formation of neocrystallisations and eventually crusts). Previous research has studied the weathering forms and the mechanisms from which they are originated, some others identified the main environmental parameters responsible for the deterioration and highlighted that both intrinsic (glass composition) and extrinsic (environmental parameters) factors influence glass degradation. Nevertheless, a clear quantification of the impact of the different deterioration extrinsic factors has not been performed.
  
  
  METHODS
  By analysing the results obtained with model glass (durable and nondurable) exposed in the field, this paper proposes a simple mathematical computation evaluating the contribution of the different weathering factors for the early stages of exposure of the stained glasses.
  
  
  RESULTS
  In the case of non durable glass, water runoff was identified as the main factor inducing the leaching (83.4 ± 2.6% contribution), followed by gas (6.4 ± 1.5%) and particle deposition (6.8 ± 2.2%) and adsorbed water (3.4 ± 0.6%). Moreover, it was shown that the extrinsic stimuli superimposes with the impact of glass composition to the weathering.
  
  
  CONCLUSIONS
  Those results show that the role played by dry deposition, even if less important than that of the wet deposition, cannot be neglected.
authors.affiliation: Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), Universités Paris-Est Créteil et Paris Diderot CNRS, 61 Avenue du Genéral de Gaulle, 94010 Créteil, Cedex, France. lucile.gentaz@lisa.u-pec.fr
authors.forename: Lucile
authors.initials: L
authors.lastname: Gentaz
authors.forename: Tiziana
authors.initials: T
authors.lastname: Lombardo
authors.forename: Claudine
authors.initials: C
authors.lastname: Loisel
authors.forename: Anne
authors.initials: A
authors.lastname: Chabas
authors.forename: Marta
authors.initials: M
authors.lastname: Vallotto
mesh_terms: D001154:Art; D017610:Calcium Compounds; D055598:Chemical Phenomena; D045424:Complex Mixtures; D005740:Gases; D005898:Glass / Q000737:chemistry*; D008956:Models, Chemical; D010087:Oxides; D052638:Particulate Matter / Q000737:chemistry; D013499:Surface Properties; D014867:Water / Q000032:analysis; D014887:Weather
chemical_list: D017610:Calcium Compounds; D045424:Complex Mixtures; D005740:Gases; D010087:Oxides; D052638:Particulate Matter; C518454:potash; D014867:Water; C016538:lime