Reconstruction of Brass for Tongues and Shallots from Baroque Organs
The composition and microstructure of historic tongues and shallots from reed pipes of various Baroque organs have been studied. They contain Cu–Zn solid solution (α-brass with 23-29 wt. % Zn) and lead particles. Grain size in brass scatters from 10 to 200 μm. Around 50% of all GBs in brass are Σ=3 twin GBs. The high-indexed coincidence site lattice facets were observed in twin GBs. The increase of number of various facets roughly correlates with decreasing grain size. It may indicate the variation in annealing temperature used by organbuilders in Baroque Era. New brass with 25 wt. % Zn and 2 wt. % Pb has been prepared for reconstruction of historic tongues and shallots by restoration of reed pipes in Baroque organs. The morphology of lead inclusions and twin GBs has been investigated in temperature interval from 400 to 700°C and compared with that of historic alloys. The annealing temperature has been estimated.
Andreas Öchsner and José Grácio
B. Baretzky et al., "Reconstruction of Brass for Tongues and Shallots from Baroque Organs", Defect and Diffusion Forum, Vols. 258-260, pp. 397-402, 2006