Description Using Antithesis

In some of my reading, I have come upon a style of describing situations that I find fairly interesting.The authors use the antithesis or an anti-description as creating something that is very vivid.

For example, from a recent reading:

“The words seemed to drip from her mouth, not like water, but like mayonnaise”

Or another one:

“The plane was packed, not like a sardine can, but like an ER and with the same smell”

By using a negative description first, it creates a mental image (since as people we don’t do well with negatives – i.e. don’t think of an elephant), and the following clarification then replaces something in the image in a vivid way. Not a break through, but I do find this effective.  Something to think about when we are trying to create a vividness in a story.