The ways in which the fabric is presented to the action of the flame may vary depending on the
type of machine and article to be treated and is particularly important for the final result:
right-angle burn on loose tissue (see figure A) is the most common;
tangential burn (figures C and D) is used for delicate fabrics and above all to eliminate
protruding fibers (light burn);
fabrics composed of heat-sensitive fibers (such as polyester) are often protected by adopting
a water-cooled roller (fig. B, point 1);
when the fabric has to undergo the operation on both sides you will need two point-blank devices,
one for the forehand and the other for the reverse.
Some machines install four point blank devices, two for each side of the fabric.
It is very important to adjust
the gas-air mixture, so as to have a prevalence of the latter;
the flame, which must not be bright, therefore oxidizing, otherwise it leaves carbon residues
and sooty on the cloth.