Our guide to the Roman Baths in Aqua Sulis is explaining the function of the implement she is holding.
Apparently, naked Romans, after enduring the equivalent of a sauna while covered in olive oil (albeit scented with, eg, lavender), would scrape the resulting 'gloop' of sweat, dirt, and olive oil from their skin into a bucket using the scraper.
If you were a famous gladiator, or a rich society lady, the ubiquitous slaves would sell those buckets of gloop to others further down the social pecking order, who would use the gloop as face masks and lotions. Presumably in the hope that a little of that success would rub off on them...?
Which explanation might explain the look on Rong's face?