It's very easy to make your own natural brown ink for writing, drawing, or crafts. Here is a brown ink recipe you can try.
Thames & Kosmos Chem C1000 Chemistry Set, Science Kit with 125 Experiments, 80 Page Lab Manual, Student Laboratory Quality Instruments & Chemicals
Lemon Juice Secret Writing: DIY Invisible Ink Science - Team Cartwright
Science Notes Posts - Page 169 of 248 - Science Notes and Projects
Fun Chemical Reaction Experiments - Little Bins for Little Hands
Use chemistry to make writing inks of many colors.
Fizzing Colors, DIY for Beginners
Secret Messages With Invisible Ink!
How to Make Ink and Paper At Home
Science Notes Posts - Page 169 of 248 - Science Notes and Projects
Science Notes Posts - Page 169 of 248 - Science Notes and Projects
Make DIY Invisible Ink! Neat Chemistry Experiment to make Science Fun!
Experiment: How to make invisible inks from a lemon, milk and baking soda
Invisible ink - Wikipedia