Depth of water incorporation into float glass surfaces studied by neutron reflection

Specular neutron reflection is used to depth profile noninvasively water in corporation into float glass surfaces as a function of immersion time. The effective nanometre resolution of the technique, allied with the contrast v ariation method, has uniquely revealed the presence of two layers containin g water. The first layer occurs at the glass surface and has a thickness th at remains constant at 30 Angstrom under conditions of 100% relative humidi ty. The second layer penetrates ever deeper into the glass as the time of i mmersion lengthens, and is accompanied by a loss of material from the glass itself.