Patents Assigned to Alex Wilson Coldstream, Ltd.
  • Latent image ink
    Patent number: 5443629
    Abstract: A latent image ink particularly for use in printing forms such as games or coloring books. An offset lithographic press is used for imprinting a substantially invisible image on a sheet of standard paper. The latent ink used to form the latent image is a mixture of potassium ferrocyanide or other suitable color foxing iron complexing compounds, white ink and varnish. A developing solution such as ferric chloride or ammonium sulfate is subsequently added to the paper to render the image visible.
    Type: Grant
    Filed: May 27, 1994
    Date of Patent: August 22, 1995
    Assignee: Alex Wilson Coldstream, Ltd.
    Inventors: Jacqueline M. Saville, William G. A. Ferguson