This engobe has high plasticity and is sticky, it is intended for use on leather-hard ware. The leather hard clay resists absorbing the water from the engobe (although it does soften somewhat) and just waits for it to catch up. Then the two shrink and dry together, forming a good bond. If the piece is dry, however, the wet engobe quickly slakes and wets the surface, pulling pieces away as it shrinks.
Engobes are high-clay slurries that are applied to leather hard or dry ceramics and fire opaque. They are used for functional or decorative purposes.