I was not sure we could build a fire hot enough to melt glass. The typical fire burns at about 900 degrees and 1400 degrees is required to melt glass (I found out from the book - I did not know that). Gavin had a pretty good fire going when I suggested that we 'melt glass'. We constructed an 'oven' as the book suggested and scavengered our neighbors recycling bins. Gavin placed a glass bottle in the newly configured fire. We were fortunate it was such a windy day so the fire was easily stoked without us huffing and puffing.
We built up the fire on top of the bottle as the book instructed and waited.
You can see how round the mouth of the bottle is and the shoulders are so well-formed. We were supposed to watch for the glass to 'slump' because it was so hot it would lose its shape.
See the curved mouth of the bottle? The kids were poking it with sticks and it was pretty maleable. Eventually the whole bottle collapsed onto itself and it was a mushy mess!
Dangerous? Absolutely. This was one of the hottest fires we have made in the backyard. I think the specific constrution of it, the vast amount of wood we put on and the wind contributed to that factor. We tried to roast some marshmallows while waiting for the bottle to 'slump', but they kept catching fire.
Have fun melting your own glass!