To test the sponges, we made scrambled eggs with no oil so the eggs would stick to the skillets. We then washed the skillets with the sponges. Some sponges were effective, but others never got the job done.
We grouped the sponges in our lineup into three categories: cellulose or soft foam rectangles with abrasive pads attached to one side, soft foam cores encased in semiabrasive fabrics of different materials, and two outliers. One of the outliers was made entirely of silicone and covered with tiny bristles on two sides. The other was made of foam: the disk-shaped Scrub Daddy of Shark Tank television fame, with cutouts forming two eyes and a smiling mouth (to wipe silverware clean) plus ridged “hair” for scrubbing.
Four of the kitchen sponges we tested were made from cellulose, a material derived from wood pulp. The wood fibers are softened with chemicals to create a viscous slurry. Salt crystals are added and the mixture is poured into a mold and set. Next, the salt is washed out, leaving behind the holes that make sponges porous. Before packaging, the sponges are usually treated with magnesium chloride (a kind of salt), which keeps them moist.
Five of the sponges in our lineup were foam, mostly polyurethane, a type of plastic often used in paint and varnish. To make them, two liquid chemicals are pumped into a large trough, along with a catalyst. As the components mix, they foam up and expand dramatically in size. The mixture is set into buns, cut into sheets, and then cut into individual sponges.
Silicone is an unusual material for a sponge, yet we were intrigued by the manufacturer’s claims that this “stay clean” sponge dried faster and harbored less bacteria than traditional sponges. Most silicone sponges are injection molded. The liquid silicone rubber is mixed with a catalyst and injected into a mold, where pressure, heat, and the catalyst cause the rubber to solidify.
Our top sponge, which is made of cellulose with an acrylic foam scrubbing surface, was very absorbent and durable.
We preferred sponges that were easy to wring out and dried quickly. To see if some were drippier than others, we submerged the sponges in water, wrung them out thoroughly, and then placed them on skewers above small bowls so we could monitor how much water accumulated.
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