Crumbwise

Guides

Is my sourdough starter moldy? When to throw it out

Most scary-looking starters are fine. A few signs mean it must go in the trash — here's how to tell.

Throw it out if you see

Pink, orange or red streaks or tint; fuzzy, dry or furry patches of any color (white, green, blue, black); or spots that sit on top like tiny islands. Don't scrape it off — mold roots go deeper than you can see.

Usually harmless

Grey or dark liquid (hooch), a dry crust on the surface, a sharp vinegar or nail-polish smell (acetone means hungry), and bubbles or foam.

Start fresh safely

Use a clean jar, fresh flour and water. If you have dried starter or a friend's starter, you'll be back to baking in a couple of days.

When unsure

Take a close photo in daylight and run a starter check in Crumbwise. If it's still unclear, the safe choice is to discard.

Crumbwise is an AI bread coach: photo checks for starters, dough and loaves, a baking planner and reminders.