Our Austrian salt deposits were formed around 250 million years ago. But how exactly did this "white gold" end up here in the Alps? The explanation dates back to 1877, with Swedish geologist Carl Ochsenius' "bar theory":

Experiment: Water Dissolves Salt

Materials:

• Glass plate or low bowl
• Salt
• Semolina
• A magnifying glass or microscope

Procedure:

• Add water and some salt crystals to glass container.
• Using the magnifying glass or microscope, observe as the salt crystals shrink in size until they fully dissappear.
• Try the same method with water and semolina. What do you observe?

Experiment: Physical Separation Methods

Materials:

• 1 glass of water
• 1 spoonful of salt
• 1 spoonful of semolina
• Coffee filter
• Cooking pot

Procedure:

• Pour salt and semolina into glass of water, stirring well, until salt has fully dissolved.
• In order to separate this solution of salt, water, and semolina back into its component ingredients, various filtration and seperation methods are required.
• Semolina can be filtered out of the solution by pouring the contents of the glass through a coffee filter; the semolina is visibly separated out and left in the filter. Taste the filtered water. Was the salt filtered out as well?
• In order to separate the salt from the water, a different phyiscal method of separation is necessary. Pour the salt solution into a pot and bring to a boil until the water has evaporated. In the bottom of the pot, a white residue will remain - give it a taste!

Experiment: 3 + 1 = 3 ??

Materials

• Lidded glass jar
• Salt
• Semolina

Procedure

• Fill the glass jar to approximately 3/4 full with water, and mark the level of the water.
• Add your salt, mixing well, until it has fully dissolved. Check the water level after adding and dissolving salt.
• For a comparison, try the same procedure with an equal amount of water and semolina (in the same quantity as the salt in the previous steps). What do you conclude?

Explanation

A salt crystal is composed of many extremely small pieces that are not visible to the naked eye. When a salt crystal comes into contact with water, these little pieces of the salt crystal slowly crumble apart.

In order to understand how this works, it helps to imagine water having little "spaces" or "gaps" between the miniscule components of water. The dissolved salt pieces fit perfectly into these little gaps. Because the salt pieces fit between the water molecules, they seem to dissappear, and the water level remains the same!

Before the invention of canning and refrigeration, one of the most common methods of preserving food was salting. Salt was traditionally used to preserve meats (salting, pickling), fish (eg. salted herring), vegetables (sauerkraut, kimchi), and more. This trick to extend the lifespan of foods dates back as far as Ancient Egypt, where it was used to preserve food for seafaring journeys.

Experiment: Make Your Own Pickles

Materials:

• 1/2 kg small cucumbers
• 1/4 Liter vinegar
• 1/4 Liter water
• 1 tbsp. salt

Procedure:

• Place cucumbers in a bowl and cover with cold water, then let rest overnight. Rinse and dry the next day.
• Add cucumbers and herbs (eg. tarragon, dill, grapeleaves with whole peppercorn) in a clean jar or container in layers.
• Mix your vinegar and water and pour into the container to fully submerge cucumbers.
• Cover the container with a plate, weighed down by a rock or other heavy object.
• Allow the cucumbers to pickle for at least 4 weeks, with regular monitoring. In the case of a layer of yeast or mold forming on the surface, remove and rinse the pickling cucumbers and replace the vinegar solution.

Tip:

To prevent mold and yeast, the pickling solution can be topped with a neutral cooking oil. The oil can later easily be removed from the surface with a spoon.

As far back as 1500 years ago, people in Eastern parts of the globe were already capable of cooling food and drinks. Using crushed ice sprinkled with salt, they created a sort of cooling solution that was able to cool to temperatures as low as -21° celsius. 

This method reached Europe hundreds of years later via sea trade. In winter, blocks of ice were cut from frozen lakes and streams to be stored in cellars with straw as insulation in order to save the ice to cool drinks in the summers. When extreme cold was required, the ice could be crushed and mixed with salt to achieve colder refrigeration.

Experiment: Refrigerating Solution

Materials:

• ca. 1/2 kg ice or snow
• 150 g salt
• Glass jar or other container
• Mixing spoon
• Hammer
• Kitchen towel

Procedure:

• Fill kitchen towel with ice cubes and place on a sturdy, shatterproof surface. Using the hammer, crush the ice into small pieces.
• Fill your jar or container with 2-3 cm of crushed ice, topped with a 1 cm thick layer of salt. Repeat this process until full.
• Stir thoroughly, and insert thermometer in the solution before it solidifies to watch the temperature sink.

Explanation:

When salt and water are mixed, the salt will always want to dissolve in  the water. In order for this to happen, the water must be liquid, and in the case of this experiment the ice must melt.

The salt begins to melt the surface of the ice, where it immediately dissolves in the resulting water. This reaction requires heat in order to function, and the necessary heat is absorbed from the surrounding environment. As the heat is absorbed by the reaction, the surrounding environment is cooled, reaching temperatures as low as -21° C!

This technique has been used as far back as ancient Roman times. The Romans used salt that built up on the walls of their stables, known as saltpetre or nitrates, primarily Ammonium nitrate. Ammonium nitrate is formed when manure is broken down by bacteria. This technique was also used by Napoleon's armies, though primarily as a byproduct of the production of gunpowder, which consisted of Saltpetre, charcoal, and sulfur.

In order to reach Salzwelten Hallstatt, you will first have to ride the scenic funicular up to Hallstatt high valley. Then, on the “pathway through time”, you will pass through the world-famous burial grounds, have an opportunity to visit a reconstructed grave and attend a Celtic burial ceremony, finally reaching the Knappenhaus at the entrance to the salt mine. After your guided tour of the world’s oldest salt mine, you will stroll along the footpath back to the mountain terminal. Before riding back down, we highly recommend paying a visit to our spectacular Hallstatt Skywalk “World Heritage View” lookout platform, from where you will be treated to amazing panoramic views of Lake Hallstatt and the surrounding mountains.

The themes covered in the “Underground Classroom” are perfectly suited for children 6 to 15 years of age.

The guided tour through the salt mine lasts approximately 1 ½ hours. In total, you and your class will spend around 3 hours at Salzwelten Hallstatt.

In order to give you and your students the best experience possible, we limit the maximum group size to 70 people.

Temperatures inside the Salzburg salt mine constantly hover around 8°C year-round. Regardless of the weather outside or season, inside the mountain is always cool. Which means, always ensure your pupils are wearing warm clothes and sturdy shoes. If you do, nothing will get in the way of exciting hours spent inside the salt mine!

The guided tours are in German or English. However, other languages are also available using the "Salzwelten Destination Guide", which you can download for free from the App Store or Google Play Store. 

Due to the relatively restricted local circumstances, the only parking for buses is a municipal bus parking area in Hallstatt. Please park here. That said, you must reserve a bus slot in advance by going to www.hallstatt-parking.com. Without a bus slot, you will be unable to enter Hallstatt. Furthermore, you cannot drive up to the entrance of the salt mine directly. PASSENGER ALIGHTING AND BOARDING: AT THE BUS TERMINAL