This is really the first object we read about in the poem, just as we're getting settled in. It might be a little hard to even tell what it is at first. Combined with the poem's title, and the rest of the first stanza though, we figure out that this is the kind of thing you would wear to protect your eyes in a lab. Good thing, too, 'cause these two are brewing up some mean potions.
- Line 1: A glass mask is definitely not a warm and fuzzy image. Coming right at the beginning the way it does, it helps contribute to the atmosphere of coldness, danger, and isolation that runs through the poem. You'd only need a glass mask if you were working with something dangerous. Browning wants to feel how far away we are from the world of light and happiness and love.
- Line 41: Near the end of the poem, she takes off the mask. Her work here is done, and she can finally take off the mask and leave the hellish laboratory. This last bit about the mask also helps us see how reckless and obsessed she is. If the mask is a symbol of her dirty poisonous schemes, it also represents safety, caution, and protection. She's willing to toss all that out the window in order to accomplish her goal.