A hard crust is the result of a burn test conducted by Navy Capt. Lynn E. Welling, the 1st Marine Logistics Group?s surgeon, in an effort to study how polyester materials, commonly found in high performance wicking material, react to fire. A concern among commanders is these types of fabrics will melt to the skin of servicemembers when exposed to extreme heat or flames, commonly encountered during roadside bomb attacks. Currently, wearing polyester materials, which includes some types of Marine Corps issued clothing and undershirts, off forward operating bases in Iraq is prohibited because of the burn hazard. - A hard crust is the result of a burn test conducted by Navy Capt. Lynn E. Welling, the 1st Marine Logistics Group?s surgeon, in an effort to study how polyester materials, commonly found in high performance wicking material, react to fire. A concern among commanders is these types of fabrics will melt to the skin of servicemembers when exposed to extreme heat or flames, commonly encountered during roadside bomb attacks. Currently, wearing polyester materials, which includes some types of Marine Corps issued clothing and undershirts, off forward operating bases in Iraq is prohibited because of the burn hazard.