First, a handpan will begin as two flat sheets of steel; one for the bottom half of the handpan, and the other for the top half. The steel chosen is dependent on what the builder prefers. Some choose low carbon steels, while others may use stainless steel. Other metals have been used as well.
These metal sheets are formed into bowls by a process called ‘sinking’. How this is done varies across the industry, but the most popular methods include hammering with pneumatic hammers, hydro-forming via water pressure, deep drawing via a large press, and rolling. These methods will not be discussed in detail here.
Once the bowls are formed, some builders choose to heat treat them. Most opt for a process known as nitriding. The nitriding process effectively hardens the steel, and when done properly, will make it more efficient to tune later on in the building process. Nitriding also creates a rust resistant layer on the surface of the steel as well.
At this point in time, the layout of the instrument will be decided upon. Magnetic templates are commonly used to layout the arrangement of notes in the inside of the top shell and are subsequently traced with a marker.
At this point, the dimples (dents in the center of each tone field) will be formed into the instrument. How this is done is dependent on builder preference. Some builders use presses, while others hammer them in manually. The function of the dimple will be discussed in a later article.
Following dimple forming, most handpans are then shaped using pneumatic hammers. This shaping process creates the tunable note areas (tone fields) in the top shell. Shaping is very similar to sculpting, and care must be taken to not over-shape the metal as it will eventually tear.
Once the instrument is shaped, the next step is commonly a stress reduction process to reduce the introduced stresses caused by all the prior hammering. The stress reduction is carried out by heating the steel in a kiln or using a large torch. The temperatures used for this stress relieving process vary widely in the industry, ranging from 300 Fahrenheit to 800 Fahrenheit or more.
Following stress relieving comes the step that makes the instrument sound the way it does; rough tuning. Up until this point, the top handpan shell may look like a finished product, but it will not sound like anything at all. The tuning process is extremely complex and takes decades to truly master. An entire article has been written on the overview of tuning, so be sure to check it out here. Most builders will perform several rounds of tuning, and between each round will stress relieve the handpan in a kiln.
Now, the bottom shell of the instrument must be made. For a traditional handpan, a port is formed in the center of the bottom shell, and its final diameter is around 3 inches. Generally, a smaller hole is first cut in the center, and then a press is used to stretch it inward at the same time widening the hole. Lastly, the sharp metal edge is usually rounded over, either by manual hammering or a machine assisted process. Some handpans will have notes on this bottom shell as well, in which case the dimpling, not shaping, and tuning process will also occur just as on the top shell.
Now that the top shell is rough tuned, and the bottom shell has been completed, the two halves are ready to be joined. The most common way to join the two halves is by gluing. Various different glues are used in the industry. Softer, more rubber-like glues will help yield a softer, less-metallic sound. However, harder epoxy-type glues have been used, and result in a more metallic sound when the instrument is played. Welding has also been used to join the shells but is generally not preferred.
After sufficient time is given for the glue to dry, the instrument must undergo several rounds of fine tuning. Over the course of a few days, or even weeks, the tone fields may drift in pitch due to the steel attempting to relax itself (a process known as strain aging). The handpan will continue to be tuned every few days until this strain aging effect largely subsides. Gently heating the nearly-completed handpan can help speed this strain aging process but must be done with care as to not degrade the glue.