GLUMA Etch are etching agents based on phosphoric acid. GLUMA Etch etchants are available in two forms and two strengths to provide dentists with a choice.GLUMA Etch 35 Gel use the traditional strength of 35% phosphoric acid. GLUMA Etch 20 Gel, with 20% phosphoric acid, provides just enough conditioning of enamel and dentin, resulting in less loss of tooth structure and equal bond strength.