A "softening agent" is something that makes something else softer.
Sentences with «softening agent»
Most commercial big - name laundry detergents contain built in softening agents, which bind to the hard water minerals, allowing the actual cleaning components to focus on fighting dirt and stains. (thinking-about-cloth-diapers.com)
If you have hard water, try adding a water softening agent like Calgon or Raindrops to your wash cycle. (nickisdiapers.com)
He washed the sheets with bleach and softening agents like glycerol. (discovermagazine.com)