Classroom Lessons

A Spy or Not a Spy
By the mere virtue of being an American in Paris in 1776, before there had been an official alliance between France and the colonies and actually before the colonies were recognized as a sovereign nation, it can be argued that Silas Deane was, in the broadest sense, an early spy for the colonies. He pretended to be a private merchant in Paris while in actuality he was procuring, at the behest of the Second Continental Congress, war supplies for the colonies’ conflict against Great Britain. He was also in possession of a recipe for invisible ink (ingredients for which included cobalt chloride, glycerin and water) for use in reporting his activities to Congress. It is also true that Silas Deane was thought by his enemies in Philadelphia to have become a traitor to the Revolutionary fight for liberty, thus having him accused as being a British spy as well. Your own research into this topic may convince you one way or the other. We have not reached any concrete conclusion but do believe that he was always a patriotic American who probably did inform his comrades across the Atlantic important information for the war effort. Let us know what you conclude about his “spy” activities on the “Feedback” section of Silas Deane Online. A CIA website is a good place to start if this is where your interests lie. Good luck!

How To Make Invisible Ink
From Anne Marie Helmenstine, Ph.D.,
Your Guide to Chemistry.
These are instructions for making non-toxic invisible ink using baking soda (sodium bicarbonate).
Its easy and takes just a few minutes.

Here's How:
1. There are at least two methods to use baking soda as an invisible ink. Mix equal parts water and baking soda.
2. Use a cotton swab, toothpick, or paintbrush to write a message onto white paper, using the baking soda solution as 'ink'.
3. Allow the ink to dry.
4. One way to read the message is to hold the paper up to a heat source, such as a light bulb. The baking soda will cause the writing in the paper to turn brown.
5. A second method to read the message is to paint over the paper with purple grape juice. The message will appear in a different color.

Tips:
If you are using the heating method, avoid igniting the paper - don't use a halogen bulb.
Baking soda and grape juice react with each other in an acid-base reaction, producing a color change in the paper.
The baking soda mixture can also be used more diluted, with one part baking soda to two parts water.
Grape juice concentrate results in a more visible color change than regular grape juice.

What You Need:
Baking Soda
Paper
Water
Light Bulb (heat source)
Paintbrush or Swab
Measuring Cup
Purple Grape Juice (opt.)

Although we would have loved to pass on to you the recipe for invisible ink used by secret agents during the Revolutionary War, the CIA has locked that recipe away in its vaults and does not want it shared. If you type “invisble ink” on your search engine, you will find many recipes and many stories about its uses throughout the ages, but no recipe that Silas Deane may have used. Maybe time will change this policy. Let us know.

Silas Deane

Congress, 1774

Benjamin Franklin

Benjamin Franklin letter