Keratex Hoof Hardener strengthens, hardens & protects hooves. Keratex Hoof Hardener strengthens weak, worn and cracked hooves by improving the molecular structure of the horn itself. Keratin is the main protein constituent of horn and is best described as the building block of the horn structure. Keratex Hoof Hardener works through a cross-linking process that results in additional atoms being distributed between the keratin molecules to produce a tougher and stronger horn structure. Keratex Hoof Hardener works by actually improving the structure of the horn itself. Since Keratex Hoof Hardener is neither a varnish or resin layer, it leaves no visible coating therefore the treated hoof is able to breathe and function naturally.