Thanks, everyone! Particularly to those who had logical reasons for why they might have excluded it and to those who listened to the commentary. Mystery solved!
If you want to dispute this, take it elsewhere.
You could interpret that as either:
We knew it was supposed to glow, but someone screwed up and it didn’t glow.
We forgot (or didn’t know until after the fact) that it was supposed to glow, and therefore didn’t tell the fx guys to make it glow.
Either way, they acknowledged that it was supposed to glow, but didn’t, so someone dropped the ball. Not that big of a deal IMO. I agree that non book reading audiences might’ve been a bit confused to see it glowing, since there was no explanatory bit in the movie about why Glamdring glowing when orcs were near.
How about… As a wizard, Gandalf exercises a greater degree of control over magic items than non-wizards. The glowing of swords near orcs is like an early warning system. Once Gandalf knew there were orcs around, there was no point in having his sword glow other than to attract unwanted attention, so he turned it off.
It’s like if you wake up before your alarm clock goes off and turn it off.
Clearly Gandalf did this off frame.
Maybe Gandalf with all his power could control the glow?
I think the “someone forgot it” explanation is better but I’ll throw that one out there too.
Well, it would have been visually distracting. (Not as distracting as Aragorn not getting Anduril until the 3rd movie under the circumstances he did, but still, it would be distracting.) It’s one of those things that works great in a book but not so well in a visual medium. I agree that it sounds cool but I think it would have to be very carefully done to succeed.
For what it’s worth, Tolkien appears to indicate that Glamdring glows even more strongly than Sting in the presence of Orcs. When the company is attacked at the Chamber of Mazarbul, “Glamdring shone with a pale light, and Sting glinted at the edges.”
I am, at best, ambivalent about the movies as a whole, and that makes perfect sense to me. I also think it was a mistake to have Aragorn yelling “Elendil” when he leaps to attack the Orcs at the end of the first movie. It’s distracting and contributes nothing to the overall movie-watching experience.
I thought not having Glamdring glow was a deliberate change from the book, in order to make Sting more unique.
I can’t remember where I heard that, though. One of the DVD commentaries? An online interview? My own crazed imagination?
lissener, let me politely suggest that you missed the point of the thread. You’re talking about consistency on the part of Tolkien, the author of the book. The OP is in fact talking about the movie. The question is not “Why did Tolkien break his own rules and have Glamdring not glow?” which is the one you seem to be replying to. (I take your reply to mean: “Tolkien just made a mistake because he’s not perfect – it is not necessary to create a bogus in-universe explanation so we can pretend he is perfect.”) Rather, the question the OP is asking is “Why did the makers of the FOTR movie not have Glamdring glow, as we were told in the book that it should?”
In other words, it’s a question about the movie makers’ choices in adapting the book, not an attempt to solicit a “fanwank” explanation (i.e. retroactive in-universe explanation) to explain a consistency error by the author.
Hopefully I’m not out of line here . . . I’m taking Marley’s above comments to mean “This is not the place to argue whether lissener’s comments/tone are appropriate for the CS forum”, not “No further response to these comments is permitted in this thread”. I’m responding to the substance of lissener’s comments (in a hopefully uncontentious way), not the tone or appropriateness.
My suspicion is that it didn’t further the plot to have Gandalf’s sword glow.
It seems to me that, when we see Sting glowing in the movies, it’s doing so specifically because the characters need a warning of orcs in the area.
We were watching The Two Towers on TNT on Saturday night. When Frodo and Sam are in Osgiliath, Frodo pulls out Sting, and threatens to stab Sam in the neck. Osgiliath’s lousy with orcs at that moment, and Sting should be glowing…but it isn’t. I theorize that, because the “spidey-sense” aspect of that glow didn’t further the plot in that scene, it wasn’t added.
Taking that logic further…in scenes when Gandalf draws Glamdring, it’s usually already obvious that orcs are about. Thus, Glamdring glowing would add nothing, except for fanboy appreciation. 
This, really.
They didn’t want to risk confusing the audience with more than one glowing sword. It was deliberate. I took definitely have the sense of having heard this somewhere, probably on the DVD commentary.
Also, WRT to yelling “Elendil!” I disagree - it’s a fan nod and does no more harm to people who have no idea what he’s saying that having him yell “YAAAAAAA!”, “GERONIMO!” or “GRMFRBLMAAARG!” as he makes the jump.
I beleive that in the Book, Gandalf also has Frodo pull out Sting to check it for “Orc detection”?
Think back on the whole series. Does Gandalf have any power other than sometimes causing a glow? :dubious: 
He rarely displays his power, because doing them is contradictory with the overall mission of the Valar & Ainur at this point in Arda’s history. I mean, if the Valar thought it was best to remove Sauron by superior force, they could have sent Tulkas over to bitch-slap him and be done with it.
Oh please. This is just the line that Gandalf uses when he’s trying to pick up women at the Prancing Pony. 
Come to think of it, the “Prancing Pony” doesn’t really sound like a place to pick up women, does it?
Ah yes. Bree.
Where “the Men are Men, and the animals are a-skeer’d”.
Gandalf never states that he is an agent of the Valar. (Sorry, I left my sense of humor in my other suit.)
I thought it was “Where men are men, and sheep are nervous.”
I t was, but the quote said “Prancing Pony” (notice lack of sheep). I tried changing the old saying to fit the quote better. 