I just posted a few different methods for disarming the Under Glass trap over in my traps gallery:

There are several potential methods to disarm this kind of trap, though depending on the particular trap implementation some of them may be more or less effective. I’ve only actually used the first two methods, the others are suggestions I’ve heard that sound plausible but haven’t been field-tested. Note that there are various destructive methods you could use to open this trap without setting it off, such as drilling a hole from the underside, but that’s considered cheating: the idea is to get the “treasure” out of the box without setting off the trap and without damaging either the box or trap itself.

• Strong Magnet: Depending on the strength and position of the popper, placing a strong magnet against the glass (or box bottom) can keep it in closed position while you remove the dome. My earlier prototype with the popper stuck to the glass could be disarmed by simply placing a very strong rare earth magnet against the glass, and then whacking the box, dome and magnet down on the arm of the couch so that the popper would snap shut from the inertia. Once the popper was closed, the magnet was strong enough to keep it closed such that the dome, magnet and popper could all be removed without setting off the cap. (Unfortunately for Jay, the version I gave him was simply too powerful even for the four large rare earth magnets I had brought with me.)

• Rice: The second option is to fill the dome with a substance that can fit through the small crack between the box and glass but still interfere with the firing mechanism. I used grains of rice, which could be forced under the dome using a thin piece of spring steel. After I had a decent amount of rice inside the dome itself I was able to lift it out of the box without firing the cap. The hammer sprung down, but wound up with a single grain of rice between it and the unfired cap. Water would also probably work, though it might damage the box or contents. Note that evacuating the dome of oxygen (for example by using a wine preserver gas) does not seem to work — I’m guessing the caps provide their own oxygen source.

• Wax / glue: We haven’t tried this, but it might be possible to carefully maneuver some sticky wax or glue through the crack in the side such that it holds the playing card to the underside of the glass dome, thus pulling the card up with the dome when it’s removed from the box.

• Flexible shim: We haven’t tried this yet either, but there exist metal shims that are extremely flexible, and such a shim might be able to actually bend through a crack between the glass and box side and get inside enough to block a popper from firing. This was essentially Jay’s strategy using pipe cleaners, but they weren’t quite flexible enough, and one of the poppers got free and went off.

Remember back to your misspent youth (or recent adulthood) spent playing Dungeons and Dragons, and how your adventuring party sweated as your thief tried desperately to disarm all the traps before opening a treasure chest? It’s in that spirit that my friend Jay and I have exchanged trapped presents every Christmas for the past sixteen or so years.

When people ask me how to disarm a trap I’m giving Jay I’ll often joke that “I just design them, disarming them is his problem,” but I actually like to know that I can get through it before I hand it off to Jay. This year’s trap almost had me stumped, and I spent almost as long figuring out how to disarm my trap as I did designing it. The trap is even more maddening because there’s nothing hidden about it — after you open the box you can plainly see all the trap mechanisms through a glass dome, just as plainly as you can see it’ll be almost impossible to get any tools at them without setting it off.

I’ve just added a write up and video of the design, called Under Glass, to my traps gallery, and I’ll be adding a write-up on Jay’s trap (which was quite cool this year) in the coming week or so.