From my experience and what I’ve been reading on hydroponic forums, people all around are having faster cloning rates using a humidity dome. Humidity domes come in many forms. A simple dome is a clear plastic structure with just a few holes for oxygen exchange. The structure sits so that it is covering all the plants without smashing them. Spraying a fine mist along the walls of the dome will help boost the humidity. The more plants per sq. inch of space will also increase the humidity, but having clones packed in too tightly could cause them to fight for light, air, and moisture. The struggle may cause unnecessary stress instead of beneficial humidity. Make sure to keep an eye on the temperature when the humidity dome is on. It may lock in heat in its enclosed structure. Simply remove the dome for a few hours so the temperature can lower and fresh oxygen can be swept to the leaves. This is a good time to re-mist the dome so the humidity is high when you put it back into action.