Traditional folded wires also use lubricants that can be trapped in the folded seam and these lubricants are usually hydrocarbons and they can form porosity in the molten weld puddle. There is an article in "Practical Welding Today" Jan/Feb 1998 which addressed this form of porosity. Unfortunately the suggestion was to rebake the wire. This solution burns off the lubricant and causes wire feeding problems and is an expensive step: taking wire out of feeder each day, storing in oven, re-issue the wire before each shift. You can imagine the cost for ovens, energy, administration, manpower and the loss of productivety to incorporate such a procedure. Seamless flux cored wires such as those from STEIN are not succeptable to moisture pickup through sheath that forms a tube (there is no seam) and these wire are copper coated. The coating improves wire feeding, current carrying capability and the source of hydrogen has been eliminated.