methods and apparatus for applying a plastic coating to woven yarn tubing to provide conduit for protecting wiring harnesses and the like . the resulting plastic coating layer is very thin so as to generally follow the contours of the woven yarn tubing , without filling in the valleys , thus minimizing the amount of plastic used . woven yarn tubing is waterproofed by impregnating with latex sealant , and is continuously pulled by a take - up mechanism along a horizontal axis through a heated die and two treating stations in tandem . each of the treating stations includes a coating pot containing liquid plastisol material and having a resilient circular exit die through which the tubing exits the coating pot to form a layer of liquid plastisol , and an infrared curing oven which heats the plastisol - coated tubing sufficiently to cure the plastisol layer . the tubing , while coated with uncured plastisol material , is not contacted by any element which would tend to deform the tubing from a circular cross section .