What precaution should be taken when dealing with ice on sight glasses?

When dealing with ice on sight glasses, using an alcohol spray is the safest and most effective precaution. Alcohol has a lower freezing point compared to water, which allows it to melt the ice without damaging the sight glass or the surrounding equipment. This method is also safe for the materials typically used in sight glasses, reducing the risk of cracking or shattering that might occur with other methods.

In contrast to this effective approach, the use of a torch could introduce excessive heat which might compromise the integrity of the sight glass due to thermal stress. Applying excessive pressure is not advisable as it can lead to physical damage or breakage. Using mechanical force, such as scraping or hammering, also poses a significant risk of damaging the sight glass, leading to potential leaks and failure of the equipment. Thus, using an alcohol spray combines efficacy and safety in handling ice on sight glasses.