Abstract: An electric iron for heating and releasing the adhesive of a bonding tape used to join fiberglass panels for insulating heating and air conditioning ducts includes a generally S-shaped resistance heating element disposed in a recess on the upper side of a planar sole plate of the iron. A body section is secured over the upper side of the sole plate and covers a layer of refractory material continguously covering the sole plate and heating element to prevent heat dissipation upwardly therefrom. Additional thermal insulation in the form of planar gaskets and layer of spun fibrous material is provided above the refractory layer and the body section is vented by openings through the walls thereof. The heating element is thermostatically controlled and is protected by a high temperature limit fuse as well as an excess current fuse. The sole plate may be made V-shaped so as to engage inside or outside corners formed by abutting panels being joined.