How to Make Rock Salt

Co-authored by wikiHow Staff

Last Updated: March 29, 2019 References

Rock salt is just coarse-grained table salt. Many stores sell it by the pound in bags. If you can't find any, then with a little work it's not hard to make your own. You can use these crystals as garnish for food, or you can keep them and add them to your personal rock collection.

Method 1

Method 1 of 2:

Making Basic Rock Salt

1
Boil some water in a saucepan. You need enough water to fill your jar. How much water you use will depend on how large your jar is.
2
Stir some salt into the water and let it dissolve. Keep the water boiling at this point. You can use any type of salt, such as: iodized salt, uniodized salt, sea salt or Epsom salt.^{[1]
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Research source} If you plan on eating the salt crystals, do not use Epsom salt.
- Uniodized salt will give you the best-shaped crystals.
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3
Keep adding salt until no more will dissolve, and a few grains remain at the bottom. If you want to make colored rock salt, add a few drops of food coloring. The more food coloring you add, the darker your crystals will become.^{[2]
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4
Take the saucepan off heat, and pour the salt water into your jar. Be careful not to get any of those extra salt grains into your jar.^{[3]
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- Some people find that placing a spoon into the jar first helps keep the jar from cracking.^{[4]
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5
Tie a string to a pencil. The string should be long enough to fit inside your jar, but not so long that it touches the bottom. About 1/2 to 1 inch (1.27 to 2.54 centimeters) from the bottom of the jar will be plenty.
6
Lay the pencil across top of jar and dip the string into the water. The string should be suspended in the water. If string won't stay down, tie a bead or paper clip to it.^{[5]
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Research source} Again, the bottom of the string should not be touching the bottom of jar. If it is, cut the string shorter.
7
Place the jar someplace where it won't be disturbed. If you can, try to keep the jar covered, such as with a box. You want the water to be able to evaporate, but you don't want any dust to get inside the jar, which can prevent the crystals from forming.^{[6]
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Research source} The room temperature should also remain consistent.
8
Wait for the crystals to grow. As the water evaporates, it will leave the salt behind. During this time, the salt will begin to come together and form crystals. Most of the crystals will grow on the strong, but you may also get some growing on the walls of the jar.
- It will take a few days for the crystals to grow. The longer you wait, the larger they will become. If you want really large crystals, you will need to use a crystal seed. Click here to learn how to grow and use a crystal seed.
9
Use the crystals. Once the crystals get to the size you want, carefully pull the string out and pour the water out of the jar. If you want to use these crystals to eat, carefully break them off the string. You can also use a butter knife to pry them away from the walls of the jar.

Method 2

Method 2 of 2:

Making Extra-Large Rock Salt

1
Boil some water in a small saucepan. You do not need a lot of water at this point, but you need enough to create a concentrated solution. Aim for about 1 cup (240 milliliters) of water.
2
Stir some salt to the boiling water and let it dissolve. Keep adding salt until no more will dissolve, and you see a few grains of salt at the bottom of the pot.
3
Pour the water into a small saucer or dish. Once no more salt will dissolve, take the saucepan off the stove, and pour the water into a small dish. You are only using a little bit of water for now, so that it can evaporate faster. You will likely have a lot of water left over. Either save this water for later, or pour it out.
- Be very careful not to get any salt grains into the dish. If you get any salt grains, your salt crystals won't be very big.^{[7]
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4
Wait until the water evaporates and crystals form. Put the dish someplace where it won't be disturbed. It will take a few hours to a day for the water to evaporate and tiny crystals to form.
5
Pick out a crystal. The crystal should be well-shaped, and not have any smaller crystals attached to it.^{[8]
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Research source} This is known as a "seed crystal." The rest of the salt crystals will cling to this, and create a perfect, cubic crystal.^{[9]
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6
Tie a piece of thread to the crystal. Tie the other end of the thread to a pencil. You can also use a popsicle stick or chopstick instead.
7
Fill a jar with more salt water, and let the water cool. Boil some more water, and add some salt to it. Keep adding salt until no more will dissolve, and you see a few grains at the bottom of the pot. Take the pot off the stove and let the water cool.
8
Place the pencil over the mouth of the jar, and slowly lower the crystal into the water. Don't let it splash into the water, if you may trigger the growth of smaller crystals.^{[10]
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Research source} The water must be cool, or the crystal may dissolve.
9
Place the jar someplace where it won't get disturbed, and wait. If you can, try to keep the jar covered, such as with a box. You want the water to be able to evaporate, but you don't want any dust to get into the jar. The temperature in the room must also be consistent.^{[11]
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Research source}
10
Use the crystal. As the water evaporates, the salt will stay behind, and collect on your seed crystal. The longer you wait, the larger your crystal will become. Once it reaches the size you want, pull the crystal out of the water, and cut the string off. Pour the salt water out. You should now have an extra-large salt rock.

Community Q&A

Question

Is it safe to eat?

Community Answer

Yes, it is safe to eat (unless you use Epsom salt).
Question

Do I have to do step 5?

Community Answer

Technically no. You will still form crystals, however they need something to grow off of. This is the use for the string.
Question

What type of salt do I need to use?

Community Answer

Any type of salt should work well.

Warnings

Make sure that the temperature where you leave the jar is consistent. A windowsill is a poor choice, because the temperatures change too much. A desk or shelf would be better.

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If you are going to keep the crystals to use for display, don't get them wet or they will dissolve.

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Don't let any dust get into the jar, or the crystals won't form properly.

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Don't disturb the jars while the crystals are forming.

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