Yield and quality in the production of cork stoppers

Abstract

Bottle stoppers of natural cork are produced from cork planks as cylinders which are bored in the axial direction. The process was followed for the production of 38 mm×24 mm (length×diameter) stoppers, using cork planks of different quality grades. The mass yield is on average 24% of the initial cork with net productions of 98 stoppers/kg and 747 stoppers/m2. The net yields are higher when using the best quality raw-material due to an increasing number of refused stoppers with the decrease in quality of the cork planks. The quality profiles of the stoppers are determined by the quality of the raw-material: i.e. ist grade cork planks produce 82% of high quality stoppers (superior and 1st class) and 5th grade planks only 22%. The results obtained allowed to establish correlations between the number of stoppers produced and raw-material parameters, namely the area and dry weight, which can be used to estimate production from a given lot of cork planks.