[header] How to make invisible ink with baking soda [title] Mix baking soda and water. [step] Making a solution suitable for invisible ink will take almost equal parts baking soda and water. For the best results, you want to mix as much baking soda as you can into a small bowl of water. 
Add a little baking soda at a time and mix slowly to fully saturate the water. [substeps] 1/4 cup (60 ml) of water will hold 3 tablespoons (43.2 grams) of baking soda.