Heating or cooling depends on your requirement. It is not a must.
As it has natural infrared, it is not a must to heat the bianstone, just use it to scrape immediately anytime you like.
The Yingyang Bianstone facial can be heated by hot water, hot air, or simply by exposing it to sunlight; or cooled using cold water. After being heated or cooled, it can be applied for scraping on the head or face or neck to improve your skin complexion.
Scientific Research shows that sibin bianstone has the power to remove excess toxins from our body....
A pair of Yingyang scraper
"The power of Sibin Bian stone with a Yingyang balance to give your face and body an extreme overlift."
Yingyang Bianstone Scraper