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92. The fifty paintings examined by the authors reveal a clear trend. Paintings
    belonging to the Florentine and Sienese schools showed double-structured
    grounds of gesso grosso and gesso sottile, identified respectively as anhydrite and
    dihydrate. Venetian examples showed a tendency towards single-structured
    grounds consisting only of dihydrate, as also observed in Gettens, R. E. and M.
    E. Mrose. 1954. Calcium sulphate minerals in the grounds of Italian paintings.
    Studies in Conservation (1):174-90. See in particular pages 180-83. The recent
    French examination finds that the examined paintings representing schools out­
    side Tuscany are not numerous enough in their material to conclude anything
    general about the treatment of grounds in the rest of Italy.


93. See note 2.


94. The wording of the Codex Laurentianus is quoted from Lindberg, B. 0. 1990.
    Feta och magra limmer enligt Cennino Cennini. In Meddelelser om Konservering,
    165-87. Lindberg notes that the Codex Riccardianus in this passage has a slightly
    different, but not clearer wording than the Laurentianus. Lindberg points to the
    fact that the manuscript lacks interior punctuation.


95. Cennini, 1960. Op. cit., 70.


96. Unfortunately, this suggestion by Thompson, which in the author's opinion is
    wrong, is apparently reflected in numerous texts on medieval grounds. See, for
    instance, Straub, R. E. 19 84. Tafel-und Tiichleinmalerei des Mittelalters. In Re­
    clams Handbuch der kiinstlerischen Techniken, Vol. I. Stuttgart Philipp Reclam, 156-


97. 
    


98. See note 8.


99. The various sources on gypsum are obviously not identical in their information
    on the relationship between the chemical composition of the gypsum and burn­
    ing temperatures. Rompps Chemielexicon. 1979. Stuttgart, 575-76. See also, Mora,
    L., P. Mora, and P. Philippot. 1984. The Conservation of Wallpaintings. London,
    Butterworth, 39-47. Also see The Merck Index, 9th ed. 1976, 1707.


100. Mora, et aI., op. cit. (note 12),42.


101. Lindberg, B. 0. , and B. Skans, in their experiments carried out at Institutionen
     fo r Konstvetenskap i Lund, have also observed that gypsum burned at 300 °C
     for two hours is still able to react with water. Lindberg, B. 0., and B. Skans. 1990.
     Feta och magra limmar enligt Cennino. In Meddelelser om konservering, 184.


102. See note 12.


103. Gettens, R. J. 1954. A visit to an ancient gypsum quarry in Tuscany. Studies in
     Conservation (1):4, 190-92.


104. Gettens and Mrose, 1954. Op. cit., (note 6), 185.


105. Theophilus on Divers Arts. 1979. Translated by G. Hawthorne and C. S. Smith.
     New York, Dover Reprints, 27.


106. A History of Technology, Vol. II. 1957. Oxford, The Clarendon Press, 118.


107. The Painter's Manual of Dionysius of Fourna. 1978. Translated by P. Hetherington.
     London, 6. It appears from the directions in the Athos book, that right from the
     mining, it is important to choose the right kind of gypsum: " ... see that you
     use only what is white and glistening."


108. Lindberg, 1990. Op. cit. (note 8), 184.


109. See note 6.


110. Bomford, D., J. Dunkerton, D. Gordon, A. Roy, and J. Kirby. 1990. Art in the
     Making. London, National Gallery. See in particular pages 17-19.


111. Martin, Sonoda, and Duval, 1992. Op. cit., 86-89, Table 2.


112. It must, of course, be below 650 °C, which is the limit beyond which the an­
     hydrite is no longer able to react with water.


113. Martin, Sonoda, and Duval, 1992. Op. cit ., 90. See also Dunkerton, J., and A.
     Roy. 1986. The Technique and Restoration on Cima's The Incredulity if S. Thom­
     as. National Gallery Technical Bulletin (10):4-27, especially page 5. See also Dunk­
     erton, J., A. Roy, and A. Smith, A. 1987. The unmasking of Tura's "allegorical
     figure": A painting and its concealed image. National Gallery Technical Bulletin
     (11):5-35, especially 19.


114. If a different crystal structure had existed for the dihydrate it would most likely
     have been included in the CSD (Cambridge Structural Database). This is not
     the case.


115. It was quite obvious that not only was the burned gypsum (the anhydrite) much
     easier to grind than the raw gypsum, but the anhydrite burned at 700 °C was
     much easier to grind than the anhydrite burned at 400 0c.


116. Cennini, 1960. Op. cit., 73.


117. Martin, Sonoda, and Duval, 1992. Op. cit., 90

Historical Painting Techniques, Materials, and Studio Practice