(under subclass 41) Processes in which the voids are formed by subjecting embedded solids to a treatment which changes the physical dimension or state of the solids and causes the space the solids previously occupied to be left as voids.
(1) Note. If the occluded solid is removed by changing it to a gas the process is here if the void is produced by the solid, rather than by the expansion of the gas. See subclass 51 for processes in which a generated gas forms the voids.
SEE OR SEARCH THIS CLASS, SUBCLASS:
51+, for processes in which embedded solids are changed to a gas and the expanding gas creates voids and see (1) Note above.
