This instructable ties in very closely with my previous instructable, Snapple, Steel and Green Fire in which the lantern that is the base and heat source for the samovar is built using re-purposed/up-cycled materials. I will give a high-level overview of the process of building the lantern, but for details, I encourage you to look at the instructable referenced above.
In Snapple, Steel and Green Fire, one of the comments (left by shizumadrive) asked if the lantern could be used to cook food. I said I thought yes, but as they say, the devil's in the details.
The first problem lies in creating a place for the food/drink to sit while it heats. Although from the top view picture, it would appear that you could just set a small pot on the grill of the lantern, in practice, doing so would cause the carbon dioxide exhaust from the lamp to smother the lamp flame. Drilling holes in the lantern top could solve this problem, but then part of the purpose of the lantern top was to reduce the level of particulates in the exhaust for the green fire version of the lamp (diboron trioxide). Holes in the top would limit this aspect of the top's effectiveness.
The second problem is in the efficiency (or lack thereof) of the arrangement. Although the lantern, being made in part of glass, is reasonably well insulated, the top is not, and that's where we need the efficiency improvements.
Making (and using) the Lantern and Samovar involves hot things and sharp things. Be careful! Cut metal is sharp metal. You will need to exercise caution when cutting and sanding the various pieces you make. Also, do not heat food or drink using the Green Fire version of this lantern. The particulate exhaust, (diboron trioxide), will almost certainly get into what you're heating. While boron is a suspected ultra-trace nutrient, you're probably getting plenty in your diet already. To quote Wikipedia "it is necessary in such small amounts that ultrapurified foods and dust filtration of air is necessary to induce boron deficiency." There is the possibility of large doses having unpleasant side-effects.
That said, I use the non-Green Fire version of the lamp and Samovar inside, and (as long as it it not left unattended), it should be no more dangerous than any other lamp or candle. Let me reiterate, however - do not leave unattended!
Boiling water + hot glass = nothing, apparently. I started this project with the idea that, worst case scenario, a boil-over could cause the glass lantern body, or even the glass of the alcohol lamp inside, to crack due to thermal stress. With that in mind, I made the first step of the project a spill tray of sufficient size to hold any alcohol that would spill in such an event. I then spent a fairly dull hour watching the water boil in the samovar, and repeatedly spurt onto the lantern top and the glass body, but nothing much happened. The water boiled off the hot surfaces immediately, but that was it.
My temperature assessing gear is not so sophisticated, but I decided to try to check the glass temperature with a standard digital food thermometer. The highest reading I got for the glass was 250° F. While this is definitely hot enough to burn your fingers, when you take into account the near-boiling temperature of the water that hits the glass during a spurt (or "bump"), the temperature difference is not really that great - about 40° F. As you will see when you read the glass cutting section of this instructable, this is not enough to propagate a crack through glass, even when a score line has been drawn across the surface. While the lid of the alcohol lamp inside certainly gets hotter than this, the glass doesn't appear to, as evidenced by the complete lack of charring, or even discoloration of the paper seal inside. I haven't had a boil over of such magnitude that water reaches the inside of the lantern, but I suspect that in this case as well, there would be no result other than to snuff out the lamp. Cold water is probably another story. Don't spill cold water on a hot lantern.
All this said, I would ask, nay implore, that you treat this as you would anything else that you have intentionally set on fire - do not leave unattended! Do not set water to boil, and then go out to (for example) mow the lawn, take a quick nap, run out to the store, finish off that last fifth of Jim Beam, chase the dragon, or engage in any other activity which absents you, physically or mentally, from the spirit samovar. This is because it is on fire, you see.