Abstract: Sympathetic ink compositions particularly adapted for use with high speed, non-impact ink printing equipment are disclosed, together with methods of use and development thereof. The inks of the invention are water-based and include of from about 4-20% by weight of a water soluble transition metal salt (e.g., nickel sulfate), together with of from about 2-4.5%, by weight of n-butanol or 2-butanol. After application using, e.g., ink jet printing equipment, the resulting inked images are invisible to the naked eye, and can be selectively developed through use of color-forming developers such as dimethylglyoxime- or oxalic acid-type aqueous compositions.

Abstract: A sharp imaging, non-smearing system for latent imaging and subsequent visual development of printed text or the like is provided which can be used on a variety of substrates (e.g. paper, metal, cloth, synthetic resins) and is extremely stable and easy to use. The system involves first imaging a substrate with an invisible non-blurring, non-sublimating ink containing a dissociable nickel salt such as NiSO.sub.4, with subsequent application of a liquid developer containing a dispersed color precursor such as dimethylglyoxime which reacts with nickel ion to give a sharp, long lasting red color. The developer preferably includes an accelerator such as NaOH for accelerating the above reaction so as to make it virtually instantaneous. The system of the present invention can be used in a variety of contexts, such as in self-testing materials or novelty items.

Abstract: A sharp imaging, non-smearing system for latent imaging and subsequent visual development of printed text or the like is provided which can be used on a variety of substrates (e.g., paper, metal, cloth, synthetic resins) and is extremely stable and easy to use. The system involves first imaging a substrate with an invisible ink containing a dissociable transition metal salt such as CuSO.sub.4, with subsequent application of a liquid developer containing a solubilized color precursor such as thiooxalic amide which complexes with dissociated transition metal ion to give a sharp, virtually instantaneously developing, long lasting color. Depending upon the metal salt selected, different colors can be obtained upon development. The system of the invention can be used in a variety of contexts, such as in self-testing materials or novelty items.