a cylindrical mass of calcium carbonate hanging from the roof of a limestone cave: formed by precipitation from continually dripping water
a cylindrical mass of calcium carbonate projecting upwards from the floor of a limestone cave: formed by precipitation from continually dripping water
Let´s try to do our own stalactites and stalagmites, with water and salt.
At first sight may look simple and easy, but in fact is a lot difficult because it will depend on a lot of variables.
What we need:
- Epsom salts,
- 2 identical glasses,
- string or paper towel,
- 2 paper-clips or weights,
- bowl or pot,
- a good place to leave the glasses siting for a few days
- Fill a glass twice with water and dump it in the pot,
- Add 1 Epsom table spoon;
- Repeat again and again until the solution is saturated;
- Heat the heat the pot on a stove, caution!
- Add more salt and keep stirring, hot water can dissolve more salt, do not boil the water;
- Split the water for the 2 glasses, try to be the more exact as you can;
- Find the location where they will sit for the next few days...;
- Leave a 3 or 4 inches between the glasses;
- Cut a string big enough to cover the distance between the glasses and hang down to the bottom of both glass;
- Tie the paper clips in both string ends;
- Place each one on a glass;
- Wait, observe ad take notes.
After a few days we will notice a little stalactite on the string.
With a bit of luck you will be able to see a stalagmite too.
The water travels through the string and the salt goes with it. While the path is vertical the salt "plays along" with water, but when the path becomes vertical, the gravity wins and the saltwater is pulled down. The water trickle and leaves the salt behind on the string. With time the salt will form a stalactite.
If you are lucky and wait enough time you will be able to see the stalagmite formation, under the stalactite.
This demonstration is not so easy as it seams.
- You need a strong and concentrate solution of salt;
- For better results immerse the string in the solution, before you place it between the glasses.
- If the water is dripping very fast increase the distance between the cups, that will reduce the inclination angle.
- Do not use a wood surface, it may damage the wood.
- Use different strings;
- Use other salts;
- Use different concentration solutions;
- Change one thing at time;
- Register everything
Dicionário de Mineralogia e geologia ilustrado
Geology in the kitchen