How to Make and Develop Invisible Inks

How to Make and Develop Invisible Inks

The speaker who makes use of chemical experiments often has occasion to use invisible inks for secret mes­sages which he wishes to develop before an audience. For this reason I shall give several methods by which you may make and develop invisible ink. In experi­ments which require such an ink, you may add novelty by using different colors. This increases the interest of the audience, and also adds to your reputation as a speaker who has a wealth of chemical illustrations.

Type of Inks and Developers

  1. Use iron chloride as the ink, and develop it by a solution of potassium ferrocyanide. This gives a deep blue color to the developed writing.

  2. Use copper sulphate as the ink, and develop it by a solution of potassium ferrocyanide. The writing will be red or gold. By combining No. 1 and No. 2 in the invisible writing, you will develop a two-toned message.

  3. Use a solution of iodide of potassium as the ink, and develop the message by a solution of corrosive sublimate which is poisonous. The writing will be scarlet. By combining No. 1, No. 2 and No. 3 inks, you may draw pictures which, when developed separately, will be three-toned.

  4. "Write with potassium iodide, and develop it by using chloride of mercury.

  5. Make an ink by dissolving two lumps of sulphate of iron in two tablespoons of water. This may be developed by the use of prussiate of potash, or potassium ferrocyanide, made by dissolving a few crystals in a bottle and shaking well.

  6. Dissolve a teaspoonful of chloride of cobalt in two ounces of water and use as an ink. This may be developed by heating the paper.

  7. Use a strong solution of saltpeter as your writing fluid. It may be developed by the use of heat or a match, which will burn out the words of the written message. Care must be taken not to burn the entire paper.

  8. Use a mixture of starch, moistened with iodine, as your writing fluid. It may be developed by heating the paper.

  9. Make a strong solution of ammonium chloride in hot water and use as an ink. Write with a clean pen. When the writing is dry, it may be developed by pressing the paper on which the message is written with a hot iron, or by holding the paper over a fire.

  10. Dissolve a few crystals of copper sulphate or bluestone in a cup of warm water. This may be used as a writing or drawing ink, which may be developed by holding over a bottle of ammonia.

  11. Use an ink made from sulphuric acid mixed with five times as much water. This may be developed by holding over a gas flame or other kind of flame.


  1. Be sure that your solutions are strong enough; this can be ascertained by experimentation.

  2. You may make inks and developers for future use.   Put them in bottles and label each one carefully.

  3. Make a list of inks and developers and key them with numbers for quick reference.

  4. When you develop a message by the heat method be careful that you do not burn the entire paper.

  5. Be sure that the ink is dry before you develop the writing.

  6. The effectiveness of the use of invisible inks is heightened when you ask someone from the audience to look at the paper to see that there is no writing on it.

  7. You may also write messages with ordinary ink, and then, when it dries, write between the lines with invisible ink. When developed the secret message is revealed. This is used by spies and government agents in sending messages from one country or person to another. However, it is always necessary to know what particular method to use in developing the invisible writing.

Types of Uses

The Sunday school teacher may use invisible messages, written with various inks, as instructions for the members of the class. Or, he may use different invisible inks to write memory verses for the children, and then develop the verses for them one by one.

For younger groups, several invisible inks may be used for drawings, which when developed will show different colors. This requires careful preparation and experimentation before hand, so that the color effects will be harmonious. In telling Bible stories to primaries and juniors, you may draw your pictures in different invisible inks before coming to the class. Then, as you talk, develop the inks one by one so that the picture which is your illustration appears as if by magic.

The story of David and Goliath, Jesus and the little lad's loaves and fishes, Jacob's ladder, etc., are suitable for these illustrations. You may also illustrate songs, such as "The Sheltering Rock," "Rock of Ages," and others that lend themselves to graphic presentation. Be sure that your drawings will develop properly and that the colors are harmonious. You may draw in outline with a thin brush, and color by brushing the proper developer over the ink.

Be very careful that you key your inks and devel­opers on the paper, so that you will know where the ink lines are that are to be brought out by certain developers or processes.

These invisible messages may also be used as the basis for programs in young people's meetings, or those of other youth groups. This is the method to follow: (a) Write in invisible ink the various items that make up your program, such as Lead Singing, Lead Prayer, Talk Three Minutes (on an assigned subject), etc. (b) Key these items with a visible number, (c) Pass the supposedly blank slips to various members of the audience, (d) As the meeting proceeds call for these numbers one by one as they appear on the program, (e) Develop the invisible-ink instructions before the audience, so that they may enjoy the novelty, (f) Be sure to match properly the inks and their developers by the use of the key numbers.

You may give these invisible inks and their developers—with instructions—to children as prizes for certain achievements in Sunday school or in children's group activities.  Children enjoy such novelties.

An interesting children's program may be worked out by writing the entire program in invisible inks and then developing it during the meeting. For instance: (a) Write the verses of Scripture which are to be read, (b) Write the names of the songs which are to be sung, (c) Write a poem to be read by one of the children, (d) Then develop these items one by one and have different children read them. Be sure to vary the inks as this adds to the children's pleasure.

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