Ingredients
- Alum powder, preferably potassium alum
- Water
- Heat-safe cup or small saucepan for preparing the solution
- Clean glass jar or clear container for growing the crystals
- Spoon for stirring
- Coffee filter or fine filter, if available
- Cotton thread or fishing line for suspending a seed crystal
- Pencil, skewer, or craft stick to support the thread across the jar
- Small dish or shallow container for forming seed crystals
- Scissors
- Paper towel for wiping drips
- Optional: safety glasses and disposable gloves
Instructions
- Prepare a clean work area. Set out the jar, stirring spoon, filter, and other supplies before heating the water. Keep the growing container away from pets, small children, and places where it might be bumped.
- Heat the water. Warm water in a heat-safe container. An adult should handle the hot water and the saucepan or cup. Hot water helps dissolve more alum than cool water, but it does not need to be boiling vigorously.
- Dissolve the alum. Stir alum into the hot water a little at a time. Give each addition time to dissolve before adding more. Continue until the solution is very concentrated and a small amount of alum no longer dissolves. Do not put undissolved powder into the growing jar if you want a clear solution.
- Filter out particles. Carefully pour the solution through a coffee filter or fine filter into a clean jar or dish. Filtering removes leftover grains and dust that could interfere with growing a clear seed crystal. Take care: the liquid and container may still be hot.
- Let the solution cool undisturbed. Place the container on a stable surface and leave it alone while it cools. As the solution cools, small alum crystals may form. Avoid moving the container during this stage.
- Choose a seed crystal. Once small crystals have formed, select one with a clear, sturdy shape. If several crystals form in a shallow dish, choose one that is not attached to the container and can be handled without breaking.
- Attach the seed. Tie the chosen crystal gently to a piece of cotton thread or fishing line. Keep the knot secure but avoid crushing the crystal. Tie the other end of the thread to a pencil, skewer, or craft stick so the seed can hang freely in the jar.
- Prepare a fresh growth solution. Make another concentrated alum solution using the same careful method: dissolve alum in hot water and filter out any undissolved particles. If the solution contains visible grains, filter it before using it for the growing stage.
- Suspend the seed crystal. Rest the pencil or skewer across the top of the jar. Adjust the thread so the seed hangs in the middle of the liquid without touching the bottom or sides. Contact with the glass can cause the crystal to grow onto the container or develop an uneven shape.
- Leave the jar in a quiet place. Choose a location with a steady room temperature and little vibration. Do not place the jar in direct sunlight, near a heater, or somewhere it will be frequently moved. Covering the top loosely with a paper towel can help keep dust out while still allowing some evaporation.
- Check the crystal periodically. Observe the crystal without stirring or shaking the jar. If it appears to be growing onto the bottom or side, carefully lift it and reposition the thread. Avoid frequent handling; crystals can be fragile, especially as they grow larger.
- Remove and dry the crystal. When you are happy with its size, lift it out carefully and let excess solution drip back into the jar. Set it on a paper towel in a safe place to dry. Do not pull hard on the thread; cut or untie it gently if it is stuck.
Notes
Use clean equipment so dust, crumbs, and other particles do not become unwanted starting points for crystal growth. The amount of alum and water needed depends on the water temperature and how much alum dissolves.
