Why not use Sting's light?

[Morthoron]

Originally Posted by The Mouth of Sauron

When the Company left the Chamber of Mazarbul, leaving Gandalf at the top of the stairs leading away from the Chamber to try and lock the door, it was stated that the Company was in great danger because in the darkness they couldn't tell when flights of stairs started and they might fall. But surely with the close proximity of Orcs if they had taken Frodo's blade Sting it would have given off enough light to guide them?

Unreliable. It would grow dimmer the further one moves away from Orcs. Besides, they had a more reliable light source, Gandalf's staff:

As the wizard passed on ahead up the great steps, he held his staff aloft, and from its tip there came a faint radiance. -- The Fellowship of the Ring, LoTR Book 2, Ch 4, A Journey in the Dark

Gandalf walked in front.... In his left hand he held up his glimmering staff, the light of which just showed the ground before his feet... -- The Fellowship of the Ring, LoTR Book 2, Ch 4, A Journey in the Dark

In the pale ray of the wizard's staff, Frodo caught glimpses of stairs and arches and of other passages and tunnels... -- The Fellowship of the Ring, LoTR Book 2, Ch 4, A Journey in the Dark