Vacuum-formed monument sign faces are an old art.

Before the advent of flexible sign face material it was necessary to form plastic to place reinforcement “ribs” in large faces to help prevent the wind from breaking them.  The best-looking way to do this was to raise the lettering, and to also raise the face close to its edges.

This was critically important in Lexan® or polycarbonate faces because the basic material is so soft that even light winds bow flat faces.  They blow out of the sign in one piece, but they blow out.

The vacuum-forming process is not used often in large modern signs because large modern signs do not have plastic or polycarbonate faces, they have flexible sign faces.

Except for cheap signs, where the face is “blistered” forward 2” or so to get the plastic away from the interior lamps without spending money making the metal sign frame of a sufficient thickness; to reduce cost.

Most people think that this has a “cheap” look, and therefore it is used mostly in secondary “program” signs; not business identification signs.

That said, the process can be used to create attention-getting visual effects, such as the airplane in the picture which would look cheap if it were flat!

   

Or, channel letter faces that separate the sign from the crowd even when it is not illuminated.