A physico‐chemical elucidation of the first photographic technology that allowed manifold reproduction is presented. An etched daguerreotype manufactured around 1840 in Vienna, preserved by the Technisches Museum Wien, served as a case study. Surface analysis showed that the photographic process involved the formation of colloidal Ag nanoparticles with sizes of 30–120 nm with shell layers consisting of Ag2O, Ag2S, and some AgCl. This breakthrough photographic technique provided a hitherto unachieved high sensitivity because of various halogenide mixtures without the use of Hg. The image development consisted of the reduction of the Ag halides by H2SO3 created by the hydrolysis of S2Cl2 leading to the formation of Ag nanoparticles adjacent to the Ag nuclei of the latent image. The fixing of the image was performed either by KCN or by Na2S2O3. The investigated plate exhibits etched areas with Ag2O conversion layers and no Cl or S. The gum arabic use for etching preferentially wetted the exposed Ag nanoparticle regions so that unexposed areas could be etched by HNO3.
The nature printing technique was designed for the electrotyping reproduction of leaves and other natural products. Authentic impressions could be performed by inserting leaves between two lead plates or pressing leaves into the lead plate by a press. The impression obtained in the soft lead plate could then be further reproduced by copper electroplating. Electrochemically deposited copper is hard-wearing and therefore very suitable for the production of printing plates. However, depending on the technical implementation and the choice of the materials used, decisive differences in the faithfulness of reproductions of original motifs may occur during the electrochemical deposition. A central topic in electroforming of printing plates is the choice of the conductive layer on the mould. In the present study, it has been shown that graphite powder represents a conductive phase on the siloxane mould superior to silver and copper powder. The grain size of the copper electrodeposit depended on the powder grain size. The copper plate deposited on graphite powder showed the lowest grain size (5–20 µm) and the highest homogeneity of the print background. Hand polishing of the printing plate resulted in a much better faithfulness of the motif details than that of the machine polished version. However, the background of the print derived from the machine polished plate was the most homogeneous. Electrochemical investigation showed that remnants of the silver powder could result in local elements that could enhance corrosion and thus impair the durability of the printing plates. This phenomenon was negligible with the conductive layers consisting of graphite and copper.
U sklopu izložbe Making Marvels: Science and Splendor
at the Courts of Europe („Stvaranje ushićenja: znanost i raskoš na europskim
dvorovima“, koja se održavala od 25. studenoga 2019. do 1. ožujka 2020.) u The
Metropolitan Museum of Art u New Yorku, SAD, izloženi su umivaonik i vrč iz
vlasništva Dubrovačke biskupije – Dioecesis Ragusina. Ta dva dragocjena
primjera renesansne zlatarske umjetnosti njemačkoga grada Nürnberga izradio je
oko 1550. godine Peter Kuster. Iako se radi o stolnom uresu i jedinim
predmetima bez vidljive liturgijske namjene, umivaonik i vrč su do navedenoga
projekta bili spremljeni i izloženi u Moćniku dubrovačke katedrale Uznesenja
Blažene Djevice Marije. Posudba predmeta iskorištena je kao prilika i povod za
opsežne znanstveno-tehnološke analize materijala i primijenjenih tehnika izrade
tih iznimnih djela nirnberškog renesansnog zlatarstva. Na temelju istraživanja
i stečenih informacija o tehničkom sklopu, upotrijebljenim materijalima,
njihovu zatečenom stanju i prijašnjim zahvatima osmišljen je koncept za daljnje
konzervatorsko-restauratorske zahvate. U radu su predstavljeni rezultati
opsežnih istraživačkih radova. Njihova interpretacija donosi nove spoznaje o
tehnici izrade naturalističkih odljeva biljaka i životinja, kao i o životu,
stilskim obilježjima, tehnologiji i značenju rada Petera Kustera. Također je
dan uvid u nirnberško zlatarstvo 16. stoljeća, te djelovanje njegova
najpoznatijega predstavnika – Wenzela Jamnitzera.
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