Asakiyume mita

Anaïs Mitchell's version of "Riddles Wisely Expounded" has these questions:

“What is greener than the grass?
And what is smoother than the glass?”
“What is louder than a horn?
And what is sharper than a thorn?”
“What is deeper than the sea?
And what is longer than the way?”

And these answers:

“Envy’s greener than the grass
Flattery’s smoother than the glass”
“Rumor’s louder than a horn
Slander’s sharper than a thorn”
“Regret is deeper than the sea
But love is longer than the way”

So here is a twofold task for you. First, can you answer one or two of the following, in comments? And then, can you add a question or two of your own, on this pattern? And, if you stop by and others have already commented, feel free to answer one of their questions rather than one of these.

What is blacker than coal?
What is more slippery than oil?
What is faster than lightning?
What is more bold than a lion?
What is more fragile than a bubble?
What is colder than ice?
What is hotter than the sun?

sovay asks,
What is sleeker than the silk?
What is harder than the stone?

sartorias asks,
What is purer than the spring waters?
What is sweeter than blossom honey?

pjthompson, commenting on Twitter, asks,
What is slower than an old woman's step?
What is more barren than an icebox? a cabinet of ice?**
What is more crowded than the head of a pin?
(She supplies answers too, but I want to see what you'll supply)
**I misremembered--this latter is her actual wording

marycatelli asks,
What is earlier than a crocus?
What is later than an aster?

pigshitpoet asks,
What is loftier than a cloud?

cmcmck asks,
What is fouler than a swine?
What is deader than a nail
What deeper than a mine?
And what is slower than a snail?

khiemtran proposes some questions that can all be answered with "Holyoke Voles." (This makes more sense in the context of this thread.)
Who are faster than lightning?
Who are blacker than coal?
Who are bolder than a lion?
(Yes!) It's the Holyoke Voles!

Who are sleeker than the silk?
Who are tougher than the Moles?
Who are harder than the stone?
(Yes!) It's the Holyoke Voles!

marycatelli has a new question duo:
What is more silver than silver?
What is more gold than gold?