Tea?

Nikon D2Xs and Nikkor 70-210mm f/4-5.6 AF lens. The lens dates from circa 1987. It is sturdy and - for a lens of this type - fairly lightweight at 665g (24 ounces). But mysteriously it increases in weight as I proceed through my planned photographic explorations of distant parts. If it keeps pulling this trick it will have to stay at home and be used only for photographing nearby domestic objects.