I knew the use of that dreaded cleaner with the soap in it was to be avoided if possible. I also knew the solution B with the soap in it was not easy to get off...particularly if it partially dried before quickly wiping it off with solution A...and it dries quicker than you can get a new pad with Solution B to wipe it off! So, I have used solution A often hoping to avoid solution B. All well and good, but eventually the soap must be used. What I should have known was that getting in a hurry can catch a long little fiber (and some short ones) off the pad on the housing at the edge of the sensor cover and wouldn't you know those little fibers are tenacious and always stick out on the sensor and rarely blow off! They are not easy to get off! I was able to get mine off using a very fine tweezer, a shaky hand and a large magnifying glass. I also learned to NEVER blow on my sensor with my mouth. Invariably microscopic spital will land on the sensor, and while it may not show up much THEN it will bake on leaving terrible spots over time. That is when the soap solution will be needed for sure. All ended well....but maybe these comments will help someone avoid what I should have known. Charles