Multitouch display, build your own: paper on the silicone rubber layer

Thanks to the first great suggestions from Cirrus and Cerupcat from NUI Group, this morning I tried an early workaround to solve my problems with the silicone rubber. Some indications came out also from Gravano and, actually, we're quite sure that the silicone rubber failure is most probably due to its excessive stickiness.

This silicone rubber stikiness is the cause of the high cohesiveness of the rear projection surface on it and this frustrate the whole screen surface setting off the FTIR effect without any finger touch. Most probably this is why any other touch is not detected and why it seems there is low IR light: because it exit the plexiglas on the whole surface and not only in the touch spots.

To confirm those assumptions, as Cirrus suggested, I tried to place a paper sheet on the silicone rubber and tested it with and without the rear projection film on it. Cirrus rightly suggested to use tracing paper but, unfortunately, I don't have it at home and today is sunday, so I gave a try with normal A4 printing paper. Here are some pictures:

The above picture is the IR camera view that shows good blobs of my fingers on the bare silicone rubber layer. This is a little bit more than what I should have also with the rear projection film on it. But unfortunately this is (still) not happening.

The above picture is made placing a paper sheet on the silicone rubber layer. It is sticking anyway but really less than the rear projection film. The stiked paper makes a noisy pattern and just around the three fingers touches.

Last picture is with the rear projection film on top, so the paper is laying in beetween the silicone rubber and the projection film. As you mai notice, the paper is adhering not only around the three fingers touch but in the large area where it is covered by the projection film, this is because the (even small) weight of the projection film is pressing it on the silicone.

This result is really really more relaxing than what I got on the first silicone rubber test. The blobs are slightly visible using a sheet of paper beetween the two layers! This means, of course, that tomorrow I will run to the shop to buy a piece of tracing paper big enough to cover the whole screen. The tracing paper should work better than the normal one, so I hope to get brighter blobs.

I don't want to consider this issue closed and run too further but, if the tracing paper will work, next step will be to build an holding structure for the screen, so I can avoid to use the kitchen chairs to hold it and switch to a pretty stable and fine-tunable setup.