[article]
Titre : |
Lime speck |
Type de document : |
texte imprimé |
Auteurs : |
Mary Dempsey, Auteur ; I. R. Hughes, Auteur |
Année de publication : |
1974 |
Article en page(s) : |
p. 12-15 |
Note générale : |
Bibliogr. |
Langues : |
Anglais (eng) |
Catégories : |
Chaulage Chaux Cuirs et peaux Taches
|
Index. décimale : |
675 Technologie du cuir et de la fourrure |
Résumé : |
Lime speck, which is first clearly recognised in the pickled pelt as white spots or areas, was experimentally shown to originate in the painted skin According to X-ray analysis and microscopical examination the defect is due to gypsum (CaS042H20) within the grain layer. While painted skin piled for one day before pulling remained clear, skin piled for three days or four days developed speck. The effect was aggravated at raised temperature and by drying, though skin which was still moist at the end of piling could also become speckled. X-ray analysis of limed, bated, and pickled pelts showed that calcium carbonate (in the form of calcite) was the precursor in the limed pelt of speck in the pickled. Nevertheless, calcium carbonate present as calcite in the lime used for the paint did not affect the incidence of speck. It appears that calcite as precursor is formed in situ and, so long as sufficient calcium ions and carbon dioxide are available, will form if, during piling, water is extracted from the system by the collagen fibres (tending to plump under the alkaline conditions) or by the fleece (competing with the pelt for water) or by evaporative drying.
The small amount of calcite found in the clear limed pelt appeared to have been directly transformed into gypsum in the clear pickled pelt, but an intermediate, vaterite—another form of calcium carbonate—occurred in the affected bated pelt: its role in the transformation to gypsum is not understood.
The practical implications of the work are: duration of piling should be kept short, skins should be piled cool and in a cool place, conditions encouraging skins to heat in pile and conditions that could allow evaporative drying to start should be avoided. |
Note de contenu : |
- EXPERIMENT I : The effect of drying and duration in pile - X-ray diffusion analysis - Results
- EXPERIMENT II : The effect of composition of the lime used, duration and temperature in pile, and position of the pelt in pile - Results
- Table 1 : Composition of lime (Exp. II)
- Table 2 : Effect on duration and temperature on incidence of speck
- Fig. 1 : Section through grain of speckled pelt, where the spots were discrete. Photographed between partially
- Fig. 2 : Diagram to show the piling of pieces in Experiment I, B and C |
En ligne : |
https://drive.google.com/file/d/14h849ao9XmG_6ZyJI6mHyymq23GVqeb4/view?usp=drive [...] |
Format de la ressource électronique : |
Pdf |
Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35481 |
in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 58 (Année 1974) . - p. 12-15
[article]
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