Simply place the timer and eggs into the boiling water and slowly watch the color change from red to white, moving from the outside to the center. When the color changes to the extent you want, you can fish out the delicious hot spring soft-boiled eggs. No need for guesswork and frustration. This way you can choose how to cook soft, medium or hard eggs. Use the color change timer to enjoy your eggs just the way you like them. Our timer displays cooking levels by absorbing heat and temperature, and the color-changing patterned layer makes it easier to visually understand the doneness of your food. Monitor the hardness of the eggs at any time according to different colors, and leave the cooker timer in the pot with the eggs. Once the color reaches the desired proportions shown on the label, it's time to pack the eggs. The timer is made of food-grade resin material, safe for food. Marks left by polishing on the bottom are normal and will not affect use.