Bioactive glass scaffolds have been developed with interconnected macropore networks, with pore diameters in excess of 500µm and apertures in excess of 100µm, by foaming sol-gel derived bioactive glasses. Bioactive glasses bond to bone by forming a hydroxycarbonate apatite (HCA) layer on their surface on contact with body fluid, which is similar to the composition of the apatite in bone. The aim of this work was to investigate the how changing the atomic structure of the glass affects HCA layer formation. Scaffolds were synthesised at 3 sintering temperatures and were characterised using 29Si and proton MAS-NMR, from which the silica network connectivity and Si-OH groups were quantified. The rate of HCA layer formation decreased as the number of Si-OH groups decreased, confirming the role of Si-OH groups in HCA layer formation.