The influence of additions of excess PbO to Pb(Mg1/3Nb2/3)O-3-35 mol% PbTiO3 (PMN-35PT) on {111} single-crystal growth by seeded polycrystal conversion was studied in the range of 0-5 vol% PbO. PbO volatilization and hence weight loss during annealing was controlled effectively by a double-crucible type of arrangement. PbO additions increased boundary mobility significantly in PMN-35PT, thus facilitating single-crystal growth by seeded polycrystal conversion (SPC). This is attributed to the formation of a boundary wetting PbO-based liquid phase. The growth process occurs very rapidly initially, after which it slows down. This is presumably due to both a decrease in the driving force for boundary migration because of an increase in matrix grain size, and a transition to lower mobility facets. It is also shown that for a given annealing time, the size of the grown crystal scales with the lateral dimensions of the seed crystal.