Question for Watchmakers, Re-Casing: Humidity and contamination

[Brushpup]

I have wondered about this many times and never heard it discussed much. I recently saw this video from Patek and just wondered what SOP is with most Watchmakers.

There have to be times and locations where watches are more likely to be closed with high humidity in the air or other potential for contaminating the case environment.

Here is the video for anyone interested. In this step, the watch is heated before being finally sealed. See step 6.

http://patek-institutional.com/conte...g/default.html