Melting wine bottles without using a kiln is no easy task, for the simple reason that glass has a melting temperature of about 1400 – 1600 degrees Celsius, and you’d be hard-pressed to generate that amount of contained heat without a kiln. Here is the guide for How to Flatten Wine Bottles without a kiln. There are theories and speculations about using a microwave oven to do the necessary healing. Still, the first obstacle to that idea is that domestic microwave ovens top out at slightly under 300 degrees Celsius. That temperature barely gets us a quarter of what we need to melt the glass, so how do we get the rest?
The thing is, we don’t, or rather we can’t unless we choose to rely on specialized equipment. And what better-specialized equipment can we rely on other than a kiln made for the purpose? However, since we are avoiding using the kiln, we’ll explore the other possibility of relying on a blowtorch to generate the required heat for our experiment.
Depending on the type of blowtorch you have at hand, you will be able to achieve temperatures of about 1100 degrees to 1900 degrees, which should be more than enough to melt down the glass for you. It now comes down to application and whatever other problems one might run into in the process of melting down the glass with a blowtorch. It cannot definitively be said whether using a blowtorch to work on a wine bottle will suffice to do the job, but we will melt one part of the bottle time, going by the achievable temperature. Would that suffice for your purpose?
It might be possible to flatten a wine bottle without a kiln if you heat it with a microwave oven for a while and then continue the process with a blowtorch, it will, at the very least, be a long task, and the success of it is not guaranteed.