Why thermoforming took over
Wrapping the face around the core and injecting foam into the perimeter makes the whole paddle act as one piece. The edges stop being dead, which enlarges the area that plays well, and the extra stiffness returns more energy to the ball.
For a couple of seasons this was simply better, and every brand that could do it did. The paddles that defined that period are all thermoformed: the JOOLA flagships, the Six Zero Double Black Diamond, the later Selkirk Luxx runs.
The failure mode, which is the whole point of this page
Thermoformed paddles fail by delaminating: the face separates from the core, usually at the perimeter, and it happens inside where nothing is visible. The paddle looks immaculate.
Worse, delamination frequently makes a paddle hotter rather than deader. There is a trampoline effect that reads as free power, so the owner often believes it is playing better than ever and says so honestly when selling it. This is why delaminated paddles are banned from sanctioned play rather than simply treated as worn out.
A traditional paddle does not do this. When one dies it goes dull and quiet, which is obvious to anyone holding it, and the failure is slow rather than sudden.
How to check before you buy
Hold the paddle loosely and tap slowly around the whole perimeter with a knuckle, listening rather than looking. A sound paddle gives a consistent tone with a predictable change at the very edge. Any section that rings differently from its neighbors is the signature.
Then press firmly on the face in several places. Softness, give or a faint crunch underneath is core crush, and that applies to both constructions.
Every thermoformed paddle that reaches this shop has had that check run by hand, and one that fails is declined rather than graded down and listed cheaply. A dead paddle is not a cheap paddle.