Epolin developed an ink for Microsoft Corporation which is visibly clear but absorbs near-infrared light. The product was originally numbered DT2-74A. Today the product is named Spectre™ 340.
Spectre 340 is a solvent based screen ink which is available in standard sizes of 30ml, 100ml and 1 liter containers.
Click here to see photographs of Spectre 340 printed on clear film