A method is disclosed for coating glass containers to provide improved tensile strength (hence improved resistance to internal pressure). The coatings so produced are durable and, in particular, resistant to the treatment steps associated with recycling of bottles. The method lends itself in particular to implementation as part of a continuous production process by utilising residual heat from thebottle casting step. The ability to recycle and the use of residual heat from an existing process offer considerable environmental benefits.