Via Mom4Real: Home Tips and Tricks for Busy Moms, mom4real.com:
You’ll need liquid dish detergent (any brand will do), baking soda and citric acid, usually found in the grocery store near the canning jars. Castile soap can be substituted for liquid dish soap.
You’ll also need silicone ice molds (any shape will work, but squares seem to make sense) or regular plastic trays.
Be aware that the recipe foams quite a bit once the ingredients are mixed together.
This makes it difficult to pack the mixture into the molds. Wait until the foaming has stopped, wipe away the excess and use it to fill another tray. Different dish liquids can foam more than others, so mixing and filling times may vary.
If your molds make tabs too big to fit the dispenser, just toss a tab onto the dishwasher floor before you start your machine.
HOMEMADE DISHWASHER DETERGENT TABS
Yield: 20-24 tablets
— 1 cup baking soda
— 1/4 cup citric acid
— 1 tablespoon dish liquid
Add all three ingredients to a large bowl. Mix well using a whisk or your hands.
When mixed, push the mixture into your molds. Wait about 10 minutes and level them using a butter knife or your hand (the tabs will slightly expand).
Let them sit for at least 4 hours or overnight. They will harden like store-bought dish tablets.
Once hardened, flip your molds over and push the tabs out. Store in an airtight container and keep dry until ready to use. They will stay potent for up to 6 months.
— Cook’n