The entry in the BDB lexicon specifically states that the meaning of raquiya is an "extended surface" and a "(solid) expanse (as if beaten out)." That makes it quite clear that we have correctly derived the meaning of the word and that it does mean a solid material that has been breaten out or spread out into an "expanse" to form the heaven above the biblical earth. The second definition in the entry further confirms our understanding that the biblical firmament is a solid structure in the form of a vault—like an upsidedown howl—that supports. or holds back, the waters above it.
KB confirms that interpretation and defines raqyia' as follows: "the beaten metal plate, or bow; firmament, the firm vault of heaven...." This lexicon also equates the firmament with the Latin firmamentum and with the Greek stereoma. An etymological dictionary of the Hebrew language provides the fallowing definition of raqiya' :"1 extended surface, expanse. 2 firmament. sky. [From raqa' ; lit. 'something beaten out]'
These references thus confirm that raqiya' has the literal meaning of something "beaten out"such as a piece of metal that has been beaten out into a sheet or plate. If one continues hammering a metal plate on one side repeatedly, the plate will gradually turn into a bowl. That, in fact. was how metalworkers in some early cultures made metal bowls and is how some metalworkers still make them.
From
here, p 84