The technology used by Gruppo Sanpellegrino to provide an inner protective coating on 50 cl PET bottles, entailing the application of an extremely thin (0.0001 mm) layer of silicon oxide, acts as an additional barrier against the loss of carbon dioxide.
Thanks to this technology, half-litre Sanpellegrino bottles are able to ensure a constant level of effervescence of their contents even under conditions of stress during transport, such as temperature changes, long bottling-to-shelf times, and climatic differences in the various countries of destination. 
Bottles processed using this technology are still 100% recyclable. Furthermore, the bottle producer estimates that the inner coating will make it possible to reduce the weight of the PET bottle by 17% with respect to the current version.