Spy Training

Every spy needs a good recipe for making his or her own invisible ink. Here are two tried and true recipes that will help you in writing all of your secret messages. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003239178/f932c3cd-843a-41cf-b19a-636fdef9a979/content/fig4_26_76.jpg"/>