Ingredients
- 2 cups baking soda
- 2 tablespoons water, plus up to 1 additional tablespoon only if needed
- 8 small waterproof treasures, each about 1/2 inch to 1 inch wide, such as plastic gems, small toy animals, polished stones, or large beads
- 1/2 cup white vinegar for the fizzing activity
- 8 small cups or bowls, one for each treasure
- 1 medium mixing bowl, at least 2 quarts
- 1 measuring cup
- 1 tablespoon measuring spoon
- 1 silicone spatula or sturdy spoon
- 1 baking sheet or tray, about 9 by 13 inches
- 1 sheet parchment paper, about 12 by 16 inches
- 1 small funnel or spoon for pouring vinegar, optional
- 1 box of disposable gloves, optional for sensitive hands
- 1 washable table covering or drop cloth, about 3 by 4 feet
- 1 old towel, for wiping hands and spills
- 1 pair of child-safe safety goggles for each child helping with the fizzing, optional but useful
Instructions
- Cover the table before you begin, because the drop cloth catches powder, drips, and the enthusiastic little spills that happen when children squeeze their first rock.
- Set up the work area. Place the drop cloth on the table, then set the parchment-lined baking sheet in the center. Arrange the treasures, mixing bowl, measuring tools, and small cups where you can reach them without crossing over the wet mixture.
- Choose and inspect the treasures. Set one waterproof object into each of the 8 small cups. Avoid anything sharp, hollow, fragile, or small enough for a young child to swallow.
- Measure the dry ingredient. Add 2 cups of baking soda to the mixing bowl. Break up any compacted lumps with the back of your spoon so the water distributes evenly instead of forming wet pockets.
- Add the water slowly. Stir in 2 tablespoons of water. If it will not hold together when squeezed, add the remaining 1 tablespoon of water in small portions, stirring after each addition.
- Test the texture. Pick up a small handful and squeeze it firmly. It should hold the shape of your fingers like damp sand.
- Make the first half of each rock. Scoop about 2 tablespoons of the mixture into your palm and press it into a rough mound. Place one treasure in the center, then add enough mixture to cover it completely.
- Pack the mixture firmly. Close your hand around the mound and press from several directions. Rotate it gently as you compress it, allowing your fingers to smooth the outside.
- Shape the rock. Place the covered treasure on the parchment and pat it into an uneven oval or rounded rock.
- Repeat the pattern for all 8 treasures: about 2 tablespoons of mixture underneath, one treasure in the center, and enough mixture on top to cover it.
- If a rock cracks, press the loose edges together with damp fingertips and add a pinch of mixture over the seam.
- Leave the tray uncovered in a dry room for 24 to 48 hours. Turn each rock gently after about 12 hours if the underside still feels damp.
- Place the dry rocks in a shallow tray or washable baking dish. Pour 1/2 cup of white vinegar into the small cups or use a spoon to drizzle it over one rock at a time.
- Add vinegar slowly and pause when the fizzing becomes strong.
- Once the treasure shows, rinse it with clean water, dry it with the old towel, and discard the remaining slurry in the trash after it settles.
- Wipe the work surface with a damp towel, then wash the bowl and tools with warm water.
Notes
This project suits children around 3 years and older with close adult supervision. Keep the activity outdoors or on a washable tray to mitigate mess.
- Cook Time: 35 minutes
