We worked on the BSC-4 dome today. Removal of the conflat, assessment, wipe down of welds, a light vacuum and restoration of the conflat all took place before lunch. There was one troublesome spot: please see picture below and note the beautiful grass-green color. The spot did not come of with an isopropanol wipe so John advised using a stainless steel brush on the spot and then some acetone. This seems to have worked well: please see second picture below. We took an FTIR of the spot and will post results when they arrive.