Inside CR Test Labs: Measuring washing machine performance

It’s one thing to wish away stains that are both metaphorical and real, as in Lady Macbeth’s tormented line, “Out, damned spot! Out, I say!” (Macbeth, Act V, Scene I). But in the Consumer Reports test labs, we do our darnedest with literal spots and stains in our assessments of how washing machines remove grime from a variety of common sources.

For our washing-performance test, we use industry-standard strips of sewn-together six-patch swatches (shown). Before washing (top swatch), each patch gets soaked in either cocoa, wine, sebum—that’s human sweat—or oily charcoal dust. For the Lady Macbeths out there, there’s even a blood patch, along with an untreated control patch. Several strips go into each of various normal and heavy-duty cycles in both an 8-pound and a maximum-size load.

After washing, our technicians analyze the swatches and compare the results using a special instrument, called a colorimeter. (They use the same device to analyze the swatches before washing, too.) The middle swatch shown was washed in the front-loading Kenmore Elite HE5t Steam 4778, without steam; this model scored excellent for washing. The bottom one is a reference swatch indicating how a model that rated a poor in wash performance would do. Compare that swatch to the unwashed sample at the top, and it’s nearly, well, a wash.—Ed Perratore

Essential information: Read our February 2008 report on washers and dryers, then refer to our Ratings of front- and top-loading washers and dryers to find the model that’s right for your family. And if you’re having trouble with spots, see our washing tips and laundry detergents coverage. Finally, watch how we tests washers in our labs.