Free chemistry investigation for STEM, gifted, and mixed-ability classrooms (grades 2-8). Teach invisible ink with real acid chemistry (pH). CER scaffolds, differentiation, workbook pages. THE CIPHER LAB FREE SAMPLER Invisible Ink & Acid Chemistry — Investigation 1 Try Velvet Rigor before you buy. This free 12-page Sampler contains one complete investigation from The Cipher Lab Bundle — ready to teach Monday morning. WHAT'S INSIDE THIS FREE SAMPLER: ✓ Complete teacher script for Investigation 1