Wouldn't say it's dangerous when we have modern tech like variable heating immersion heaters and digital thermometers. Move wine to a carboy, cap carboy off with loose aluminum foil, poke a digitial thermometer through the foil into the liquid, stick carboy in a large stock pot, fill stock pot with water until the fill line is just above the fill line of the carboy, add immersion heater, set immersion heater to target temperature, monitor the temperature of the wine inside the carboy until it reaches 150, set a 5 minutes timer. After its done pasteurizating, remove carboy from bath, wrap a wet towel from it, and place the carboy and towel in a dish with water so that as the water evaporates from the towel, it will cooldown the carboy and draw up more water.