If you use tap water for tea, limescale deposits will build up over time on the surface of your electric kettle or tea maker. To remove these and keep your appliances running smoothly, scale must be removed using these descaling tablets. Simply dissolve a tablet in about 8 ounces of water, and run the appliance using its 'black' tea setting. For optimal performance, we recommend descaling your kettle or tea maker once a month. Expiration date is 2024/03/09, but will still work well.