Here's a great explanation of traditional attar making from the internet:
Attar-making is a labor-intensive process, requiring great talent, skill and patience. It can take over two weeks to make a small batch of a single attar. Anywhere from twenty-five to three-hundred and fifty pounds of flower petals are collected and placed inside a deg. From the deg, a long bamboo pipe leads downward to a copper recepticle that contains sandalwood oil. Water is added to the deg, and the lid is sealed down with a mixture of cotton and clay. The deg sits over a fire and contains no modern guages or thermostats. As the steam collects, it condenses and flows into the receiving vessel.
The fire must be constantly monitered to keep the correct temperature. Too much heat will burn the flowers. It will also create too much pressure which can explode the clay seal around the deg. The low heat and pressure preserves the fragile fragrance oils better than the hotter steam distillation method used to obtain essential oils.
The receiving vessel sits in a pool of water and is continually rotated by hand to blend the oils and keep them from overheating. Throughout the day, the master distiller monitors the deg and receiving vessel by feeling them with his hands and listening to the sounds from inside. When necessary, wet towels are rubbed over the vessels to cool them down.
At the end of the day, the distillation is stopped. Overnight, as the oil cools down, the water separates from it. In the morning, the water is poured off from the oil and put back into the still. Freshly picked flowers are added, and the process begins anew. This process will be repeated for fifteen to twenty days, until the sandalwood oil is completely saturated with the fragrant oil of the flowers.