Sugar syrup repels standing water. The single most common cause of sweating, sliding tanghulu is surface dampness on the fruit. If skin retains moisture, steam forms the second the 300°F syrup touches it, separating the candy shell from the fruit and liquefying the interior layer within ten minutes.
Wash your strawberries, grapes, or kumquats thoroughly, but leave stems attached until cleaning is finished to keep water from seeping into internal cavities. Lay the fruit across paper towels and air-dry for at least 45 to 60 minutes at room temperature until the outer skins feel completely dry and slightly tacky.
When threading fruit onto bamboo skewers, pierce through firm central cores without puncturing all the way through the top. Puncturing the outer wall releases fruit juice that ruins the dip. Work in small batches of two to three pieces per skewer to keep the center of gravity low and coating motions swift.
