Free cold brew timer for overnight steeping. Smooth low-acid concentrate perfect for iced coffee. Wake up to ready-to-drink cold brew.
The sweet spot is 12-18 hours for balanced flavor - beyond 24 hours you start getting woody bitter notes that aren't pleasant. At 8 hours it's under-extracted and weak but at 16 hours it's smooth sweet and fully extracted. Unlike hot brewing where over-extraction happens in minutes cold water extracts slowly so you have a much wider window. Most people do overnight 12-14 hours which is convenient and gives consistently great results. If you like it stronger use more coffee not more time.
You can do either but they give different results - room temp extracts faster so you only need 8-12 hours while fridge temp needs 12-18 hours. Room temp risks bacterial growth if you go too long so fridge is safer especially in summer. Fridge cold brew tends to be smoother while room temp can be slightly more acidic. Most people prefer the fridge method because you can do it overnight and not worry. Just know that temperature directly affects extraction time so adjust accordingly.
Standard concentrate ratio is 1:8 or 1:4 coffee to water by weight - so 100g coffee to 800ml water or 250g to 1000ml. This makes concentrate that you dilute 1:1 or 1:2 with water or milk when serving. Using less coffee means weaker brew that can't be diluted. The concentrate approach is better because you can control strength when serving and it keeps longer in the fridge. Don't try to make ready-to-drink at full strength - concentrate and dilute gives better results.
Use coarse grind similar to French press or even slightly coarser - you want grounds that won't pass through your filter. Fine grounds over-extract and make your cold brew bitter plus they're impossible to strain properly leaving sludge. The coarse grind is forgiving because cold water extracts slowly so you need that large surface area for 12-18 hours of contact. Consistency matters too so burr grinder is worth it for cold brew just like any other method.
Undiluted cold brew concentrate lasts 7-10 days in the fridge sealed in an airtight container. Once diluted with water or milk drink within 2-3 days. The concentrate is essentially preserved by its strength but once you add water or milk it becomes perishable. Pour concentrate into smaller containers so you're not opening the main batch daily which extends life. If it smells off or tastes sour it's gone bad - trust your senses.