Another tool to talk about is THE BLACK LIGHT. Several hosts have referred to it, but I’m giving special thanks to @KKC for the photos, product link, and explanation of how it shows hidden biological specimens in the post titled, “Black Light Gives Big Fright.” Clearly, a bathroom or other space can appear to be clean, but this nifty gadget may show if there is actually major nastiness lurking there! By the way, a coordinating product to consider is the special UV protecting yellow glasses, which, according to reviews, increases the contrast of the black light. When my budget allows, I will add both of these to my arsenal. In the meantime, I am wiping down the walls around my toilet on every cleaning!
Black Light:
Yellow Glasses: