Overflow can be a pain to deal with when brewing large batches of coffee. Generally, this issue comes down to three variables: grind, dosage, and filter type. There are a few important notes to consider if your experience ever leads to overflow.
The first variable to pay attention to is your grind. Your grind consistency determines how quickly or how slowly water moves through your coffee bed. Depending on your grinder interface, you should see numbers, letters, and/or tick lines that represent grind size. You should have an adjustment collar at the bottom of your hopper (the whole beans holder on top of your grinder). This adjustment will determine the particulate size you’ll see in your grounds bin. If you adjust finer, water will take longer to drip through the grounds. If you adjust coarser, water will drip through the grounds faster. The Ratio preferred ground size is similar to raw sugar.
The second variable to pay attention to is dose. This refers to the weight of grounds you place in your filter medium. Once you find the correct grind size, you must experiment with your dose and adjust to taste. For half batch (20 oz. brew; half fill line indicator on the water tank), we suggest dosing between 35-42 grams. For a full batch (40 oz. brew; full line indicator on the water tank), we suggest dosing between 68-75 grams. Be sure to level out the grounds bed before brew.
The third and final variable that can lead to overflow is your filter use. We send every Ratio Eight with four sample Chemex FC-100 circle paper filters. This is our go-to paper filter for its ability to produce a clean cup and fit nicely with our glass carafe. When placing into the glass carafe, be sure to face the three folds toward the pour channel. This will prevent air-lock from occurring due to filter collapse into the channel. When using the Ratio Kone reusable stainless steel filter, you do not have to pay attention to orientation but it is still important to level the grounds bed before initiating the brew process.
As always, we are happy to help any time if you send us a note at firstname.lastname@example.org.