The holding time for the materials with length of 15mm or longer will extend by one hour on the basis of 3 hours for every 15mm or less increasement ; and the holding time will extend 13min for every 0.3 inch increasement on thickness.
on the basis that 3-hour heat-preservation is available, the material with the length being larger than or equal to 15mm is subjected to heat preservation by more one hour once the length is increased by 15mm or is less than 15mm, and is subjected to heat-preservation by more 13min once the thickness is increased by 0.3in.