The activation of thermoplastic sheet materials by means of a water bath at 65°C / 149°F goes faster than a dry heater due to the much higher heat transfer rate of water compared to air. On the other hand, those splints will cool down faster when molding due to the remaining water layer which remains present on the surface. The evaporation of this thin water layer subtracts the heat on a much higher level compared with dry heating. Another aspect which is influenced when using water is the stickiness: the small water layer also acts as a non-sticking layer; it will prevent the splint from sticking more than dry heating would.
The activation by means of a dry heater is more hygienic due to the lack of water. As there is no water layer involved on the splint, the crystallization time is longer, which gives the therapist or splint fabricator more time to fabricate the splint on the patient. The splint will also have a more sticky feeling as there is no water layer present. This additional stickiness can help the fabrication process by means of the so-called “third hand”, allowing the material to stay in place while the therapist positions the extremity and forms the design.