Crystal Formation Plan


- Two 250ml beakers
- A filter funnel and filter paper
- A source of hot water
- A stirring rod
- Tweezers
- Tongs
- Spatula or plastic spoon
- Some fine nylon thread
- Watch-glass or paper hat to fit on one of the beakers Ruler
- Smart phone or digital camera
- Diary or log book to record observations.


Tuesday - Day 1

1.  Make sure all equipment is clean and dry.

2.  Place approximately 25g of potash alum in a beaker and add approximately 170 ml of hot water. Stir the mixture until all the crystals have dissolved. The solution may have a slightly cloudy or milky appearance.

3.  Filter the warm solution through a filter funnel (in which filter paper is inserted) into another clean beaker. Cover the beaker of solution with the watch glass or fresh filter paper and set aside in a cool sheltered place and allow it to stand undisturbed overnight.

Wednesday - Day 2

4.  The next day, observe the beaker of solution. The bottom should have become covered with a layer of smallish crystals which formed spontaneously as the solution cooled. Carefully pour off the clear solution above the crystals into a clean beaker and set it aside for later, leaving the crystals behind in the other beaker.

5.  Let it stand overnight again and observe the formation of crystals.

Thursday - Day 3

6.  From the crystals, one symmetrical crystal or group of crystals needs to be selected to act as “seed” for your big crystal. Using a plastic spoon, spatula, tongs or tweezers, to move the selected crystal to the beaker containing the solution, trying to place it centrally in the beaker.

7.  Take a picture of the crystal, rather closely to a ruler so that you can measure its size, and mark the level of the liquid in the beaker. Record the date in your diary.

8.  Cover the solution with a loose-fitting paper hat that allows water to evaporate slowly whilst keeping out dust. (Keep the temperature as constant as possible)

Thursday onwards

9.  Once a week, record in your diary the level of the solution in the beaker and take a picture of it close to a ruler so that you can estimate how much it has grown. Avoid disturbing crystals during the growth phase.

10.  If small isolated crystals appear, you have to carefully remove them with tweezers. Be careful not to disturb your big crystal. If small crystals grow on the main crystal, remove it, dry it with tissues, and carefully remove the buds. Do not touch the crystal with your fingers. The crystal is likely to be quite fragile, fairly brittle, and easily damaged.

11.  Allow the crystal to grow. Continue to monitor progress by reporting in on the drop in water level, and estimate the size of the crystal.

12.  When no further growth is obvious, a new solution may be prepared as before (dissolving the crude alum in warm water, filtering off any impurities, and decanting the solution after it has cooled overnight).

13.  When the new solution is cool enough, your crystal may be transferred into this new solution and may then continue to grow as it takes up more of the aluminium potassium sulphate salt from the solution.

14.  When it is decided to finish the experiment, remove your crystal very carefully from the beaker, dry it with tissues and with a ruler measure its length, width and height.

15.  Compare the measurement with the size of the original crystal. Take a photo of completed crystal