The phrase "as soft as cotton" is correct and can be used in written English. You can use it to describe something that is soft or smooth, such as fabric. For example, "This sweater is as soft as cotton.".
The cakes are deep-fried until the crust is tempura-crispy, the inside as soft as cotton, and then they are served beneath baby asparagus and poached eggs.
"Water is as soft as cotton," he told me looking out over the Channel on a sunny day with ferries gliding past.
It's as soft as cotton mixed with cashmere and that's what we use a lot. .
After slightly altering the song, as well as adding his verses, Dogg met with Carey once again for her approval on the song, "When I played [the finished version] for her, she was like, 'Oh, I love it!' I said, 'OK, give me a hug, baby.' She was just as soft as a cotton swab!
It was just too difficult to put all the pieces into place — crisp cotton sheets, comforters as soft as marshmallows and thousands of fluffy pillows — and then to keep the whole setup looking right.
He looked as soft as a sponge.
"May soil be as soft as down".
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union