Pretend you’ve been recruited as a member of the Culper Spy Ring, and you need to know how to decipher a message written in invisible ink. Supplies include a paint brush, water, drying cloth, vitriol (diluted sulfuric acid), Thomas Jefferson cipher and “furnace box.” Read the clues to find the coin with a hidden message, reveal the message using the brush and vitriol, then use the cipher to decode the message.

Contact: Nancy Locquet Absillis, nancy.locquet@naturalsciences.org