After viewing a
web video showing the boiling of water in a plastic bottle in a fire without melting the bottle, I decided to try it. Of course it's a variation of the same trick, performed with a paper cup in which the cup won't completely burn until the water is gone via evaporation.
What interested me about this is the survival implications. "Boiling water" has long been part of standard survival advice and fire-making a key survival skill. Most survival kits include firemaking equipment so you could boil water - if they also included a container.
Per the directions in the video, I began by trying to completely fill a 20 oz. Poland Springs bottle after removing the label (I speculated that the label might catch fire). I was unable to get it filled without an air bubble but this might actually be easier in a survival situation. If taking water from a stream, one could submerge the bottle and squeeze it to force out any air bubbles and then cap the bottle before removing it from the stream.
I then placed my bottle in the side of a hot fire pit with a lot of coals but only a few flames. After a number of minutes, the water inside the bottle began to boil. The bottle itself was doing ok with the exception of the cap which began to melt from the outside when licked by a tall flame on one side. Note that this was the location of the small air bubble. Finally, the bottle began to bulge and I removed it from the fire chopstick style using two pieces of wood. After cooling, the water tasted flat as boiled water should.
Later, I reenacted the famed high school physics experiment and boiled water in a paper cup. Since that campout, I've repeated the experiment using an unopened bottle of water with similar results although this time I did not remove the label. The fire burned it off. The water boiled. The cap, the interface between the air bubble and the flame, melted.
But what about disinfection and chemical safety?
Disinfection: What temperature was the water inside? I'm assuming that it reached 212 F (100 C) because it boiled. It should be noted that when allowed to cool, the water inside remained much hotter than the plastic outside for quite some time. While older recommendations were to boil water for 20-30 minutes for disinfection, more up to date recommendations are to bring the water to a boil. Once it reaches boiling temperature it is disinfected. So my water would have been disinfected and safe to drink from that standpoint.
Chemical Safety: Was the plastic evaporated into the water? I'm not sure but don't think so. Frankly though, in a survival situation I would accept what might be a minor increase in long term cancer risk to avoid the risk of debilitating sickness due to microorganisms.
Tips For Enhancing The Process
- Allow no air in the bottle. No air bubble means no melting.
- Do it in hot coals or very low flames to further avoid chance of melting.
- Remove bottle if it begins to bulge.
- Use tongs made from green wood or two long sticks as "chopsticks" to remove the bottle.
- Allow the water inside to cool.
- Although the paper cup trick shows that you could use an open container, the advantage of a lid is that you won't spill your precious disinfected water.
There is plenty of room for further experimentation. For example, how would a ziploc bag fare? A turkey bag? A Nalgene bottle?