Korean grandmothers stay in tubs seemingly for hours.
But the optimal length for a pre-scrub soak is 30 minutes.
Soaking in hotter water causes the skin to wrinkle faster (a good thing), but according to a gaggle of ddemiri (scrub mistress) at Geumgansan Sauna in Hapjeong, customers should stay in the water temperature they're most comfortable with, instead of attempting a hotter tub and calling it a day after a few minutes.
"Staying in the water to prune is most important," says one ddemiri.
3. Be completely bare
This one may seem obvious, but scrub mistresses say many of their customers come to them without removing everything.
This includes rings, earrings, glasses and other accessories.
Those with long hair should bring their own hair-tie -- the ddemiri will tie their hair in a perfect bun.
4. Seriously, relax
"Relax!" is the instruction issued most often by the ddemiri.
If the body is too rigid, the scrub mistress can't contort it into the positions necessary to get at every nook and cranny.
It's awkward and painful at first, but forcing the body to relax its muscles allows the ddemiri to get things done most effectively.
"Usually customers listen and then they end up having a lot of fun," says Jung.
5. The fun should come afterward
This one surprises locals as well as foreigners.
Though some think sitting in a spa's various hot rooms before a scrub is an effective way to get the skin ready, ddemiris advise getting scrubbed before relaxing.
"If customers get scrubbed first and then go to the hot rooms, they'll feel more refreshed, since the sweat isn't blocked by dirty pores," says Jung.
"Then all they have to do after is rinse off in the shower."
6. Scrub weekly
Scrubs should be booked once a week.
Any more often, and there's danger of over-exfoliation.
But according to Jung, weekly scrubs improve skin vibrancy and blood circulation, as well as muscle relaxation.
Jjimjilbangs to hit up for the best scrub
Dragon Hill Spa, 40-713 Hangangro 3-ga Yongsan-gu, Seoul; +82 2 797 0002; open 24 hours; ?11,000-?13,000 ($10-$12)for admission, scrub prices vary
The Spa in Garden 5, 5/F 10, TOOL Da-dong Garden5, 292 Munjeong-dong Songpa-gu, Seoul; +82 2 404 2700; open 24 hours; ?6,000-?8,000 ($5-7)for admission, scrub prices vary