Because putty with high moisture content (about 25% or so), curing and drying with the loss of moisture, will cause contraction, putty layer thicker, shrinkage is larger, therefore, putty layer too thick will cause putty layer cracking phenomenon, so we asked the Nizi batch blow each batch scraping can not be too thick, if the required number of scraping thickness is larger, the need for construction of a number of. Conversely, if the putty layer number of scratch thin, it will cause the excessive moisture loss, putty layer of binder can not be fully into membrane to bonding, leading to dry off after the phenomenon of powder. Therefore, we require control of putty scraping monolayer thickness in 0.5-1 mm.