What are pinholes? Pinholes are miniscule holes or porosity in the aluminium foil, There are European guide lines as to size and quantity of pinholes tolerated (see NEN-EN-546)
Various causes for pinholes in the aluminium foil are slag in capture from the supplier, impurities in the ingots (Direct Casting) and coils (Continuous Casting ), mill filter installation malfunction or impurities entering the mill, wrong combination or percentage of rolling oil additives, too high reductions, just to mention a few.