What is a hot patch, and how is it done?
1.A hot patch is rarely ever used in this day in age. As mikes stated, it's mainly a vulcanization process of melting or welding the two pieces of rubber together. I've only ever used plugs to patch a hole. Larger ones may require two plugs. I have never had one fail and I've probably done well over a hundred of them.
2.I have never used any of these techniques. This is how is was explained to me by an "old guy" who by the way, had never done it either. The shop I worked in had been around for years and we had stuff that was never used. One was the vulcanization kit. Maybe it was an excuse to sell more tires or liability isses. Years ago tires were always patched.The repair was made by "vulcanization". The process was either chemical,thermal or a combination of both. In the chemical process either two chemicals were mixed and they generated heat or a rubber softening chemical was used to soften the rubber. The thermal method involved a hot metal iron. The patch is clamped in place intil it has set. The end results were all the same, rather than the repair being glued in place the repair was basically a weld with rubber. Maybe with the cost of tires it is gaining popularity again.
3.A hot patch is a round small metal cup with rubber sealient on one side and flammable material in the cup. It is clamped onto the tube or tire and the flammable side is punctured with a sharp tool and set on fire, it then bonds the rubber side to the tube or tire.
4.The hole was prepared the same as a cold patch. The hot patch was clamped in place with a special clamp. The patch was lit with a match and the patch was vulcanized to the tire.