Ground spices release their aroma more quickly into a dish as all the flavour compounds and volatile oils are exposed. First choose the texture you want. For a fine, even grind, an electric spice grinder is best. Using a pestle and mortar gives you more control, so is good when you want cracked spices or a coarser grind, and is also convenient for small quantities. Adding a little sugar to act as an abrasive and an absorbent can be helpful, especially for oily cardamom seeds and cloves or sticky mastic.