Immediately before bonding, aluminum sheet surfaces to be bonded are thoroughly cleaned using a suitable solvent, such as 1-1-1 Trichloroethane. This is carried out at least twice and more often if required to eliminate grease or dirt deposits. The cleaned surfaces are abraded using 120 grit abrasive paper. Metallic/silicon carbide abrasive paper is not to be used. The surfaces are thoroughly abraded and the abrasive paper changed regularly during the process to avoid clogging, which could lead to a polishing effect. Following abrading, the surfaces are thoroughly cleaned again, as above. In total, the surfaces are solvent-cleaned at least four times. All dust and deposits left as a result of the abrading process are removed, as these can adversely affect bonding. The adhesive is applied to one surface only, using a ribbed rubber roller. In cases where honeycomb is to be bonded to aluminum sheet, the adhesive is applied to the aluminum sheet only. A maximum pressure of 0.5 kg/m2 (11.9 lb/ft2) is applied evenly over the surface, giving a maximum film thickness of 0.5 mm (0.02 in).