Supplies of green copper carbonate often vary in color and density (darker and heavier, lighter and fluffier) reflecting variations in raw materials and manufacturing procedures. Despite variations in the physical appearance of the material, the amount of contained copper metal remains essentially constant. As with other metallic coloring carbonates, copper carbonate is bulkier than the oxide form, thus it tends to disperse better to give more even results. It is also more reactive chemically that the oxide form 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 colors are less intense than the oxide form.