like amethysts beneath my feet

If you live or work in downtown Portland, you may have noticed the little purple glass squares and circles set into the sidewalk here and there, at seemingly random locations. If you're like me (which I admit is unlikely) you might've been curious about them. They're obviously quite old and a bit weatherbeaten, but it's not so obvious what they are or what they're for. Fortunately, in this modern era, the answers are just a few keystrokes away, out there on the interwebs.

The purple glass bits are known as "vault lights". See, a "vault" is an underground area, well, ok, a vault, situated under the sidewalk or under the street proper. If you want natural light in your vault, you install some of these. Hence the name. In Canada, they call them "sidewalk prisms", which has a more poetical ring to it. It's also a bit more informative, since the lights do have prisms on their down-facing sides, for diffusing sunlight all over the subterranean vault. Flat glass on the bottom would mean a few small pools of intense sunlight, which isn't what anyone's likely to want.

Vault lights aren't all that common anymore in Portland but underground vaults are all over the place. Some are abandoned and bricked up, while others are used for storage. If you've seen the super-cool freight elevators that pop up out of the sidewalk, they exist to provide direct access to your sidewalk vault right from the street, so you can stock up your underground storeroom without hauling everything in through the front door. This can be very helpful, since our fair city generally lacks back alleys for that sort of thing.

I can't find a comprehensive list of vault lights in Portland, but I'm making notes now when I run across them. I'm certain these aren't the only ones, but these are the ones I know of right now. The largest collection I'm aware of is around the Galleria building, which is where the top two photos were taken. The south side of the building facing the MAX tracks has an array of clear vault lights, which I'm guessing may be more recent replacements for older lights. The third photo is from outside the Dekum Building, on SW 3rd around Washington or Alder, I think. A third grouping is in front of the Clyde Hotel building on Stark St. You could also count the clear lights that serve as skylights for the visitor center in Pioneer Courthouse Square. They obviously aren't any older than the park itself, but I guess we can still count them if we want to.

[Updated 1/2/07: Two more vault light sightings to report, both on the edge of the Pearl. #1, the sidewalk outside the North Park Lofts building, on the North Park Blocks at Everett. #2, outside the office supply place at 9th & Flanders. ]

I was curious why they're always purple: If that was just an aesthetic choice, or was mandated by law, or something else. Turns out the answer is "something else" in this case; the lights actually started out as clear, but prolonged exposure to UV light caused impurities in the glass to turn purple over time. In the early 20th century, it was common to add managanese to glass, to combat existing impurities that would make the glass green. That works great in the short term, but eventually your 'clear' glass turns purple, sort of potassium permanganate colored. Manganese is actually the cause of the very similar purple color in amethysts, the only difference being that amethysts are quartz instead of glass. Still, they're close cousins, and the family resemblance should be pretty obvious. Restoring vault lights could be kind of a problem; do you restore to clear glass, or to the purple glass everyone's so used to?

As an aside, if you ever see anything advertised as "vaseline glass", with a fluorescent yellow-green color, just be aware that it gets its color from... uranium. Seriously.

Back in the Galleria's heyday, the vault area was just part of the mall, and you could stand there and look up and out. You couldn't get a clear look at the foot traffic passing overhead, but you could tell they were there. I remember thinking that was very cool. Of course, I've always had a fascination with all things subterranean, I mean, the very name of this blog refers to a 50's sci-fi mole machine, so I may think this stuff is cooler than the average person might. But really, how can you not love having another entire world directly beneath your feet. That's just cool.

I have a dream here. Vault lights are cool, sidewalk elevators are extremely cool, and I just don't think either is being used to maximum advantage. Imagine, an underground bar, purple vault lights in the roof, as many as the city will let us have. And instead of carrying freight, the sidewalk elevator is the bar's main entrance. You press a call button, the elevator pops up out of the sidewalk, you hop in, and it whisks you down to a secret space beneath the feet of passersby. Decorwise, either Art Deco speakeasy, or Victorian boudoir would seem fitting. I'm not sure what I'd call the thing; the obvious choice is something using the word "vault" or "prism", but perhaps that's just too obvious. Failing that, as a geek I've always thought "/dev/null" would be a great name for a bar, although it doesn't exactly have a retro ring to it.

Further resources about this stuff:

• An extremely thorough page about vaults (a.k.a. "sidewalk basements") and vault lights. Everything you ever wanted to know, and much, much more. Plenty of photos, too.
  
• Two pages concerning city regulations of sidewalk elevators. So far I haven't seen anything that explicitly prohibits using them to carry passengers instead of freight.
• More resources about how glass gets to be purple: here, here, and here. From the first link:
  

  
  Take a century-old glass bottle, and expose it in the desert to the ultraviolet radiation present in strong sunlight. Come back after ten years, and the glass will have acquired an attractive purple color. Heat the bottle in an oven, and the color disappears. Next expose the bottle to an intense source of energetic radiation, as in the cobalt-60 gamma ray cell of Figure 24, and within a few minutes an even deeper purple color appears, as shown in Plate XI.
  ...
  A century ago, glass used to be decolorized with manganese additions to remove the green color caused by iron impurities. It is the Mn2+ left from this process which loses an electron to form the purple Mn7+ shown in Plate XI in the solarization process described at the beginning of this section.
  

  
  
• Photos of vault lights in Portland, Astoria, Seattle, and Victoria, BC.
  
• The National Park Service considers them part of the "look" of historic Lowell, Mass., and therefore worth preserving.
• As part of an award-winning restoration of Seattle's Pioneer Square, "pre-purpled" vault lights were installed.
• And two pages touching on vault lights in New York City.
• If you need to buy modern replacements for your vault lights, here's one source for them. Not purple, though.
• A mention of underground vaults in connection with persistent stories across the Old West that they were somehow connected with secret doings in the Chinese community. Our own "Shanghai tunnel" mythology may be connected to this as well.
• Off on a bit of a tangent, a piece about obscure & unusual elevators in the state of Oregon. Sidewalk elevators get a brief mention here:
  

  
  The City of Portland in the past gave out permits for sidewalk elevators so the downtown buildings could receive freight below ground in their basements. As far as anyone knows there have been no new permits issued for a long time but there are some of these elevators used today. We will not list them.
  

• An interesting, poetic blog entry about vault lights.
• Portland's sidewalk elevators get a mention in this intriguing thread about the tech behind vaults and elevators, among other things. This post discusses how sidewalk elevators work, and has this to say about vault lights:
  

  
  The glass blocks you recall being imbedded in the sidewalk were called "vault lights". As you note, some businesses had extended their basements out past the "building line" and under the sidewalk. Usually, this was done to provide working space around a sidewalk type freight elevator, additional storage or utility space (as for water,gas and electric meters) or was done to provide space for coal bins or bunkers. I have been in a few such basements in really old buildings and walked in under the vault lights. It is a strange feeling to be "under the sidewalk" and see the changing light patterns as pedestrian traffic keeps right on walking accross the vault lights with no knowledge you are under their feet. In truth, a weak light, at best, came thru the vault lights. These were solid pieces of glass imbedded in a concrete slab which the formed the roof of the "vault" or extended basement. The glass was usually quite thick, ont he order of 2 or 3" thick. Over time, the glass became frosted from foot traffic, steel wheeled carts, and the use of sand and ashes on the sidewalks during winter weather. Typically, if you looked closely at the sidewalks where there were vault lights, you would see a strip of bronze imbedde dint he concrete- this marked off the limits of the "sidewalk vault". You might also see a small cast bronze tag imbedded in the concrete giving the name of the vault light maker. I haven't been down in the old parts of NY city in years, so don;t know if the sidewalk freight elevators and the sidewalk vaults and vault lights still exist.
  

• JSTOR has the text of a book or article titled Superstitions from Oregon, but the Google search that led me there indicates there was a superstition about walking on sidewalk vault doors. Which isn't completely unreasonable, since some of them can get pretty slippery when wet.
  
• The MySpace profile of a local guy who lists vault lights as one of his interests.
  
• From the state building codes division, we learn that sidewalk elevators now only need to be inspected once every two years, instead of annually. (It's on page 4 of the linked PDF.) An earlier doc from the same agency informs us that yes, you do need a permit for a sidewalk elevator, and the pertinent safety regulations may be found in the American Society of Mechanical Engineers' A17.1 Part IV. Unfortunately I'd have to pay money to find out what that says. So first, I guess I need to find someone to fund my latest "coolest bar ever" idea, and then find out whether it'd actually be legal or not.