Abstract: The invention is a black-in-back backlit sign substrate that has an eradicable ink. The substrate is constructed of a scrim coated on the front-side and back-side with an extruded translucent PVC, and a back-side coating of an eradicable ink. The scrim is a polyester yarn having a count of 12×12 to 20×20, with a more preferable count of 18×15 to 18×18. The weight of the backlit sign substrate is in the range of 14 to 28 oz./sq yd, with a nominal weight of about 16 oz/sq yd for the 18×15 scrim and about 24 oz/sq yd for the 18×18 scrim. The tensile strength of the 18×18 scrim sign substrate is about 270 lbs/in in the warp direction and about 220 lbs/in in the fill direction. Overall, the weight of the front-side coating is preferably slightly heavier than the back-side coating to ensure that the face of the sign is very smooth. The substrate is calendered to enhance smoothness, reduce coating profile imperfections, or to add embossing.