There was a bit of a debate on G+ about the merits of our IR sensor & the benefits of painting the back of the glass black to ensure the sensor is not misled by PCB warp. Just launched a print that makes use of most of the bed and, must say the first layer went down perfectly Nevertheless it occurred that, in fact, it's only necessary to put a splash of paint under the exactly places where the IR sensor does it's thing. Perhaps no more than a square centimetre each time? (In the doc. https://miscsolutions.wordpress.com/mini-height-sensor-board/ no mention of the area the sensor scans, but seeing that it's 1.5mm from the bed it must be less than a square! ) Anyone know the bed coordinates that the IR takes it's measurements at? (Pro and Dual are different.)
It actually can see through glass if the surface under the glass is strongly reflective in the IR range. Some explanation here: https://miscsolutions.wordpress.com/mini-height-sensor-board/