An unconsolidated or loose core is retrieved and retained within a coring tool by wrapping the core with a resilient thin film sleeve. The sleeve is compacted and stored within a concentric cylindrical storage space outside of the core and within the tool. The thin film compacted sleeve is then drawn from the storage space and wrapped about the core. The thin film sleeve is characterized by having a longitudinal length several times greater than the corresponding longitudinal length of the storage space in which it is compacted and stored. More particularly, the thin film sleeve is compactly stored in a cylindrical space defined within an inner tubular mandrel concentric with the core and an outer tubular mandrel concentric with the core. The two mandrels are concentric with each other and spaced apart to form an annular circumferential opening through which the thin film sleeve is disposed and drawn. The thin film sleeve is coupled to a guide plug, which is axially disposed and longitudinally displaceable within the core barrel of the coring tool. When the core is disposed into the core barrel, it comes in contact with the guide plug which is then displaced relatively upward within the coring tool, drawing the compacted thin film sleeve from its cylindrical annular storage space about the concentric core within. Typically, the thin film sleeve is a 4 mil resin, plastic or rubber tubular, cylindrical sleeve.