Once you decided how much saffron you are going to use in your recipe, before adding it to anything else or powdering it, place your saffron threads in a clean flat dish and separate the threads by your finger and look carefully. Anything that does not look like a saffron thread, pick it out and throw it away. Often there are foreign particles mixed with the saffron threads, not intentionally but by accident. Cleaning saffron is a very labor intensive process when you deal with pounds of saffron. Saffron packers do their best to ensure the saffron is free from any foreign particles, but sometimes they miss. Since you only use a small amount of saffron, it will only take few seconds to scan the threads with your eyes. For your safety and the safety of others who eat your cooking please take this tip seriously. This is another disadvantage of powdered saffron as everything gets ground.