Chemistry
 

Question: How Does Stainless Steel Remove Odors?
Answer: One household tip for removing odors from fish, onions, or garlic from your hands is to rub your hands across the blade of a stainless steel knife. In fact, you can even buy stainless steel 'soaps', which are just hunks of stainless steel that are about the same shape and size as a bar of normal soap. Does stainless steel remove odors? If so, how does it work?
There isn't a lot of hard scientific data (that I have seen anyway) concerning stainless steel odor eaters. However, you can test this kitchen wisdom yourself, using your nose to take data. Better yet, get someone else to smell your fingers, since your own sniffer will have odor molecules inside it already from exposure to the food.
My experience has been that the knife trick works, but only up to a point. If you have been working with onions, garlic, or fish long enough for their 'perfume' to be absorbed into your skin, the best you can do is to diminish the scent with the steel. Other types of odors are not affected by contact with the metal.
How It Works
This is speculation on my part - if you know more about the chemistry behind this phenomenon, please feel free to write me. It makes sense to me that the sulfur from the onion/garlic/fish would be attracted to and bind with one or more of the metals in stainless steel. Formation of such compounds is what makes stainless steel stainless, after all. Onions and garlic contain amino acid sulfoxides, which form sulfenic acids, which then form a volatile gas (propanethiol S-oxide), which forms sulfuric acid upon exposure to water. These compounds are responsible for burning your eyes while cutting onions and also for their characteristic scent. If the sulfur compounds bind to the steel, then the odor is removed from your fingers.

How To Make Invisible Ink - Baking Soda?
 

How To Make Invisible Ink - Baking Soda?

There are at least two methods to use baking soda as an invisible ink. Mix equal parts water and baking soda.

Use a cotton swab, toothpick, or paintbrush to write a message onto white paper, using the baking soda solution as 'ink'.

Allow the ink to dry.

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.

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.)