======Growing Crystals on String======


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**Alternative titles:** Cubic Rock Salt Crystals
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====Summary====                   
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====Procedure====  
  - Heat water in a kettle, let it cool a few minutes, and pour warm (not boiling) water into a clean glass or jar.
  - Stir in table salt a teaspoon at a time until some grains remain undissolved at the bottom (a saturated solution). Let the undissolved grains settle.
  - Cut a length of cotton string and tie one end to a paper clip (this will act as the weight/seed). Tie the other end to the middle of a drinking straw so the paper clip can hang freely.
  - Bend or tape the straw so it rests across the jar’s rim and the paper clip hangs in the solution without touching the sides or bottom.
  - Add a rubber band around the jar to keep the straw in place. If loose salt is swirling, let the jar sit a few minutes so the liquid is clear.
  - Place the setup somewhere safe, warm, and still (no vibrations or direct sun). Do not disturb for several days.
  - Check after a week. If crystals are small, leave longer. If a crust forms on the surface, gently lift it off with a spoon so growth continues on the string and paper clip.



====Links==== 
Making Salt Crystals at home - Kitchen Science for Kids - Whitehorse Manningham Libraries: 
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Growing Crystals Experiment | Geology | The Good and the Beautiful - The Good and the Beautiful Homeschool Science: 
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📄 Grow Your Own Crystals - The STEM Hub: [[https://thestemhub.org.uk/stem-at-home/item/grow-your-own-crystals]]\\


====Variations====
  * Compare salts: table salt (sodium chloride), kosher salt, sea salt; observe how purity and grain size affect crystal clarity and shape.
  * Use other salts such as epsom salt.
  * Test temperature: one jar at room temperature vs one in a cooler location; record growth rate.
  * Color the crystals by adding a drop or two of food coloring to the solution (color will tint crystals but not change their cubic shape).
  * Try different seeds: rough vs smooth string, a short cotton wick, or a scratchy wooden skewer; rank which collects crystals fastest.
  * Cover one jar loosely with paper to slow evaporation and compare crystal size vs an uncovered jar.



====Safety Precautions====
  * Adult supervision required when handling hot water and glass; allow water to cool before pouring.
  * Keep small parts (paper clip, bits of crystal) away from young children and pets; do not eat the crystals from a science setup.
  * Set the jar on a stable surface where it will not be bumped; label it clearly.
  * Clean up spills promptly; wash hands and any equipment with warm, soapy water after the activity.




====Questions to Consider====
  * Why do crystals start to appear after days rather than immediately? (As water evaporates, the solution becomes supersaturated, so dissolved salt leaves solution and deposits as crystals.)
  * Why are many salt crystals tiny cubes? (sodium chloride has a cubic crystal lattice; external crystal shapes reflect the internal arrangement.)
  * What happens if the paper clip or string touches the jar wall? (Crystals may bridge to the glass, changing growth and possibly anchoring the seed.)
  * Does starting with hotter water make bigger crystals? (Hot water dissolves more salt quickly, but crystal size is mainly controlled by slow, steady evaporation and lack of disturbances.)
  * How could you grow a single larger crystal instead of many small ones? (Start with a small “seed” crystal and suspend it in a just-saturated, filtered solution; keep the jar covered to slow evaporation and remove competing crystals.)