1. Choose the appropriate sponge: Factors such as the material, shape and size of the sponge will affect its water-blocking effect. Choosing a sponge with higher density and better elasticity, and choosing a suitable sponge according to the size and shape of the test tube can improve the water blocking effect.
2. Weighted sponge: Adding some heavy objects inside the sponge, such as small stones, iron pieces, etc., can increase the weight and density of the sponge, thus improving its water-blocking effect.
3. Use a sponge clamp: The sponge clamp is a tool specially used to fix the sponge. It can clamp the sponge on the outside of the test tube mouth to prevent it from shrinking inward.
4. Use multi-layer sponges: Stacking multiple layers of sponges at the mouth of the test tube can increase the density and effect of water blocking. At the same time, you can also add some glue or other adhesives to the sponge to increase its adhesion and prevent it from shrinking inward.