will be sensed and through well known means control the operation of the heater 46 a typical trash bag made in accordance with the present invention might have a bag body made of linear low density polyethylene lldpe film approximately 1 mil thick such bags popularly range from about 0 7 to 1 5 mil in thickness it will therefore be understood that relatively low temperatures around 375 u00b0 f and brief dwell times will provide an excellent seal between two thicknesses of this material contrarily the hemmed area of the trash bags will typically include a ribbon having a thickness around 2 mils and the ribbon almost always includes some high molecular weight high density polyethylene hmwhdpe as is discussed in the parent applications in order to obtain a good weld at the edges of the bag in the hemmed area it is necessary to use a high temperature around 800 u00b0 f and use a relatively large radius on the side welding blade while one radius cannot be specified for all conditions it will be understood that a typical side welding blade used for 1 mil lldpe will have a radius of about 0 016 34 by contrast a typical side weld bar for a bag hem having the four thicknesses of 1 mil lldpe and two thicknesses of 2 mil ribbon made of hmwhdpe will require a radius of about 0 062 34 it will be understood that as the materials are harder to seal and require a larger bead for the needed strength the radius of the blade will increase and as the plastic is sealed easily with less of a bead a smaller radius is appropriate variations in the radius can be made to suit the.