Question about Logitech K740

it becomes sticky over time. I completely removed the sticky surface with alcohol. The remaining hard plastic is still very pleasant to use as a hand rest.

Hello Karogowi,
I don't think the sticky feeling is dirt, but rather the "peach skin coating" that dissolves into pleasantness. I bought my K740 in May 2010 and I still type on it. I clean the keys and the palm rest twice a month with a damp cloth, sometimes with a little liquid soap / soft soap, until it no longer sticks. The Pfirtisch skin is almost no longer there. If you want to get rid of it completely, I think only pure alcohol like isopropanol or acetone will help. But I haven't tried that myself, so try at your own risk ;-)