Others ( glass - glass ) are made with a double layer of glass fused together at one .
Both ends with a vacuum between the layers ( like a vacuum bottle or flask ) , with the absorber and heat pipe contained at normal atmospheric pressure .
Others ( glass - glass ) are made with a double layer of glass fused together at one or both ends with a vacuum between the layers ( like a vacuum bottle or flask ) , with the absorber and heat pipe contained at normal atmospheric pressure .