Uncovering lead formate crystallization in oil-based paintings

Abstract

Lead formate was found in oil paint systems, crystallizing in the early stage of polymerization of oil paints and playing the role of an intermediate in the degradation of lead pigments.

Reconstructing Reliable Powder Patterns from Spikelets (Q)CPMG NMR Spectra: Simplification of UWNMR Crystallography Analysis

“…Trimesitylaluminum—AlMes 3 —and Trimesityl-tetrahydrofuran-aluminum—AlMes 3 ∙THF—were prepared and handled as described in [ 30 ]. Lead diformate—Pb(HCOO) 2 —was obtained according to the description provided in [ 35 ]. Cesium silver(I) bismuth(III) bromide—Cs 2 AgBiBr 6 —was synthetized by the procedure described in the literature data [ 41 ].…”

“…The spectra profiles based on the literature data ( Figure 1 , lit. data) were simulated in Bruker TopSpin software as fitting curves which corresponded to NMR parameters presented in respective scientific articles (see Table 1 , [ 29 , 30 , 32 , 33 , 34 , 35 ]).…”

The formation of formates: a review of metal formates on heritage objects

“…Formic acid also occurs as a by-product of the oxidation of unsaturated aldehydes: These are formed by the decomposition of primary unsaturated ester hydroperoxides from the autoxidation of oils [5] used as binding media. The acid can then react with pigments in paint layers [6].…”

“…Drying oils are another source for formic acid: Evaporation experiments proved the emission of formic acid from drying oils during their autoxidation by a tailored GC/MS procedure [6]. During the curing of model paints, lead formate was identified unambiguously by powder diffraction as a secondary product of the interaction between minium pigment and four different drying oils.…”

Long-chain mercury carboxylates relevant to saponification in oil and tempera paintings: XRPD and ssNMR complementary study of their crystal structures

“…10 Furthermore, various drying oils (linseed, poppy-seed, walnut and stand oil) were found to exhibit a different tendency to form an ionomeric soap phase as well as lead formate upon reaction with minium (Pb 3 O 4 ). 11 Moreover, the emulsifiers in egg are suspected to favour the formation of well crystalline lead carboxylates in egg-based tempera and emulsion paintings. 1,7 While the attention is predominantly paid to the investigation of the main paint components responsible for saponification, i.e.…”