The maximum allowable water and oxygen contents of the atmosphere are only one side of the successful brazing triangle shown in Figure 1.
The first leg of the triangle is the heating rate. If the heating rate is too fast, the brazement will not be at an even temperature right through when some sections reach brazing temperature. Some parts may not reach brazing temperature at all, resulting in dry joints. If the temperature is raised to compensate for this, then the hotter areas can melt. Conversely, if the heating rate is too slow, the flux will have a longer time to react with any oxygen present in the atmosphere and may become completely depleted before the brazing temperature is reached. It is generally recommended that the heating rate should be greater than 20°C (36°F)/minute, provided that a uniform temperature of ±3°C (5°F) is maintained across the brazement at the brazing temperature.