Some time back, I’ve bought some infrared blocking foil for the Virttable from the German foil store Ifoha. Infrared blocking foil is an approach for the blocking of ambient infrared light (e.g. from a light bulb or daylight) ONLY in a FTIR multi-touch setup as it blocks light that comes from above the table. I.e. in DI your hands reflect light that would be blocked by an IR blocking foil.