[kepano]

Not all materials are a good example of a self-guaranteeing promise because purity can't always be easily verified at home without special equipment.

In the example of stainless steel it is "stainlessness" that is the promise, and that only requires water to test.

[brookst]

> that only requires water to test.

Not really.

304 stainless is pretty stainless with fresh water. Not so much with saltwater. 316 is stainless in saltwater at normal temps, but not high temps. 400 series is both more stainless and less stainless than 300 series depending on conditions. And then there are the exotic ones.

And if all we're verifying is stainless after immersion in water, aluminum counts.

"Self-guaranteeing promise" is just a confusing way of saying "immutable properties after measurement".

[kepano]

I understand you're trying to be more precise, but what the average person cares about is whether the knife rusts easily or not.

I don't think the average person is going to understand what you mean by "immutable properties after measurement", though I'll concede "self-guaranteeing" is probably equally confusing.

"Verifiable and non-reversible" seems clear enough, but a bit long.