Windows are remarkable inventions—they allow us to see the outside world while still staying warm and dry inside. The problem is that windows are not nearly as remarkable or useful when they are dirty or streaked. The solution is, of course, to clean them, but care must be taken when cleaning. Cleaning windows with an inferior cleaner can be almost as bad as not cleaning the windows at all. There are some basic factors to look for to help find the best streak-free window cleaner.