| "Invisible Ink" from lemon juice...
In this activity, you will use the acidic properties in lemon juice to create invisible ink. As you may recall from "Investigating the effects of sunlight on paper.."acid weakens paper and heat accelerates the release of acid.
Procedure
1. Collect the juice from a lemon by squeezing it (you may want to wear goggles...!) or use bottled lemon juice
2. Write a message on plain white paper using a stick, paint brush or cotton bud as a pen
3. Allow the paper to dry
4. Hold the paper up to a heat source like the sun or a light globe (avoid open flames and radiators unless there is close adult supervision) 5. The heat will cause the paper affected by the lemon juice to turn brown
Some interesting facts...
Acid is a chemical substance that can weaken paper and cloth. It can cause these materials to become brown and brittle
Lignin, an organic substance present in wood pulp, becomes more and more acidic as it deteriorates. This produces the "yellowing" of newspaper. Sunlight accelerates the break down of lignin and creates higher acidity and yellowing. The cheaper the paper quality eg newsprint, the higher the levels of lignin.
PVC or polyvinyl chloride, is an unstable plastic that can emit hydrochloric acid. For this reason, photographs or paper items should be stored in ploypropylene sleeves as this is an inert plastic. Some easy steps to follow...
Acid is the enemy of photgraphs, paper items and other memorabilia. For this reason it is important that any storage or display materials are free of acid, lignin and PVC.
Do's and dont's...
- If you have, or wish to use a scrapbook, to house your keepsakes, you can test the pH of the pages and the item itself using a pH pen. The colour chart will give you a reading of the pH.
- Colour photocopy your memorabilia on to acid-free paper
- Take digital photographs of items and think about ways to "back up" this data to preserve it
- Use polypropylene sleeves to house all sorts of memorabilia from certificates to locks of hair
- Use acid free adhesives and archival mounting corners
- Don't laminate as it irreversibly traps dust and contaminants and changes the nature of the item
- Don't use "sticky tape" or other adhesives that may contain acid
- Don't put newspaper in direct contact with other paper as the acid produced by lignin can "migrate" from one to the other
Other activities...
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