One of the more interesting aspects of iodine is its unusually high vapor pressure. To the lay person, vapor pressure can be crudely summarized as the ‘willingness’ of a substance to evaporate. Pour out a puddle of alcohol, water and oil and you’ll see that the alcohol disappears quickly, the water dries later and the oil seemingly refuses to ever dry out. This rate of evaporation is the vapor pressure and believe it or not even the strongest steels, all materials in fact, will evaporate given enough time.

Iodine is on the extreme quick side of the equation. If outside of a sealed glass dome like this one it will race with that alcohol mentioned above into who disappears into thin air fastest. It will turn into a beautiful purple fume that will make you choke like you just took a lungful of strong pool chemicals too. But, back to the topic at hand: iodine is in fact so difficult to keep in its pure form that even when stored in a non-glass container or a liquid that dissolves it it will find the smallest, microscopic fissure to sneak out and break free.

For this reason these domes were made a little differently than the rest. Note on the photos that to one side there’s a curious nipple. This was actually a glass tube that was fused to the dome where the iodine vapor was piped in and then allowed to condense along the sides. A flame then severed and fused shut the dome as a final step. This differs from the other domes on this page which, if you look carefully, all have bases that are glued on. Making iodine in this standard method might work on the short term but eventually it would eat through the glue - maybe years later - only for you to one morning wake up to find your dome magically empty. So with this method there’s no way of that happening. Well, so long as you take care of the glass not breaking of course!

Each dome will have an array of crystals splashed across the internal walls of the dome. You can, if you are feeling adventurous, gently heat the dome to the lowest setting in your oven for a few minutes and the crystals should turn into that deadly-but-beautiful purple haze. As it cools down you will get a different arrangement of crystals. The rate of cooling dictates the shape and size of the crystals; something best done in a lab so don’t pout if your crystals aren’t quite as big or nice as the originals ;-)