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When I add dish soap to a sponge it is able to foam up. But if I leave the sponge alone for an hour, it doesn't foam up, not even if it is wetted.

Why? The sponge should still contain dish soap an hour later.

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  • $\begingroup$ Evaporation, perhaps? $\endgroup$ – HDE 226868 Jan 22 '15 at 1:33
  • $\begingroup$ The sponge is dry up, but the dish soap should remain in. $\endgroup$ – blackcornail Jan 22 '15 at 1:57
  • $\begingroup$ When the sponge dries, there's not enough water in it to create the air bubbles that cause the foaming. $\endgroup$ – Hot Licks Jan 22 '15 at 2:10
  • $\begingroup$ @HotLicks I see it, but when it be wet again (for example an hour later), the sponge doesn't foaming. $\endgroup$ – blackcornail Jan 22 '15 at 2:17
  • $\begingroup$ I would push for the migration of this question to chemistry.se since it is concerning soaps and detergents. $\endgroup$ – Gaurav Jan 25 '15 at 8:20
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Dish soap traditionally contained foaming agents such as sodium laureth sulfate which is chemically stable over long periods of time. But more recently environmentally conscious soap companies are turning to foaming agents that have a shorter half-life. These chemicals tend to break down sooner - perhaps just by being exposed to air. This helps reduce foaming in the settling basins of wasterwater treatment plants, or storm drains that enter the ocean and it takes less water to rinse away the soap.

Read the ingredients of the soap you are using and research to see which are the foaming agents, and what the stable half-life is.

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