As with other metallic colouring carbonates, copper carbonate is green in colour and bulkier than the oxide form, thus it tends to disperse better to give more even results. It is also more reactive chemically and thus melts better. As such, it is ideal for use in brush work where minimal speck is required. However it produces gases as it decomposes and these can cause pinholes or blisters in glazes. Also the carbonate form contains less copper per gram, therefore colours are less intense than the oxide form.
The hydroxyl component is an important aid in dispersing the powder throughout the glaze slurry and thus avoid specks in the fired glaze.
The raw powder begins to melt between 1950 and 2000F. At around 1500F it gases and will discolour nearby items in the kiln