Mattster:

Every time I go to the Laundromat, I see this sign that says the dryer works better if you put in three loads of wash instead of one. Of course I ignore the sign because it doesn't make any sense. So why is it there?

-- DJ, San Diego

So if you're only washing one load, should you borrow wet clothes from one of those people with garbage bags full of what is clearly a semester's worth of reeking Levi's? Maybe so, according to the experts. The key to the mystery is not so much the dryer but the dryer's exhaust port that vents the air to the outside. In all commercial dryers and some bottom-of-the-line home dryers, there's a moisture detector in the port that measures the air's water content as it whooshes past. As long as damp air is being vented, the thermostat keeps the heat up inside the dryer drum. But the dampness-measuring gizmo can be fooled into thinking your clothes are dry if you don't have a good tumbling action going inside the dryer. This requires a sufficiently large quantity of clothes ad a good mix of sizes and weights. Too few items will tend to clump together and stick to the drum. Air will just slide by your lump of duds and food the moisture sensor into thinking everything inside is dry. You also have problems if you put in, say, four sheets ad a pair of heavy cotton socks. The sheets will dry much faster than the socks, ad the minuscule amount of dampness remaining in the dryer drum will be the sensor's signal to cool it. The you'll pull out dry sheets and soggy socks. Another dryer mystery unraveled. Moisture sensors inside the drum eliminate the necessity of catering to the dryers wants and needs. As if life weren't difficult enough.