How to Restart Fermentation (Step-by-Step Guide)

If your fermentation has stopped before your wine is finished, don’t panic.

This is called a stuck fermentation, and it’s a common issue in home winemaking.

The key is to confirm the problem, identify the cause, and then restart fermentation properly.

In this guide, we’ll walk through exactly what to do, step by step.

Step 1: Confirm Fermentation Is Actually Stuck

Before trying to fix anything, make sure fermentation has truly stopped.

A stopped airlock does not always mean fermentation is finished or stuck.

Use a hydrometer to check.

• If gravity is still high, fermentation is not complete
• If readings stay the same over a few days, it is likely stuck

You can also review our guide on stuck fermentation for deeper diagnosis.

Step 2: Check Temperature

Temperature is one of the most common causes of stuck fermentation.

If the wine is too cold, yeast can go dormant. If it is too hot, yeast can die.

Use a floating thermometer to check your fermentation temperature.

Slow or stuck fermentation often happens when conditions fall outside the ideal range, since yeast activity is highly sensitive to temperature changes. 

If needed, gently warm the wine to bring it back into a healthy fermentation range.

Step 3: Add Yeast Nutrient

One of the most common causes of stuck fermentation is a lack of nutrients.

Yeast need nutrients to stay active and finish fermentation properly.

Add yeast nutrient and gently stir to help reactivate the yeast.

Low nutrient levels are a known cause of stuck fermentation, as yeast cannot continue without sufficient nitrogen and support.

Step 4: Gently Stir the Wine

Sometimes yeast settle at the bottom and become inactive.

Gently stirring can bring yeast back into suspension and help restart fermentation.

Do this carefully to avoid introducing too much oxygen.

Step 5: Add Fresh Yeast (If Needed)

If nothing else works, you may need to restart fermentation with new yeast.

Use a strong, reliable wine yeast and prepare it properly before adding.

Many winemakers use a starter method, gradually introducing the yeast to the wine so it can adapt and begin fermenting again. 

This step is often the most effective when fermentation has fully stopped.

Step 6: Transfer if Necessary

If the wine contains a lot of sediment or stressed yeast, transferring it can help.

Use a siphon and food-grade tubing to move the wine into a clean container.

This removes inhibitory compounds and improves conditions for restarting fermentation.

When NOT to Restart Fermentation

Sometimes, restarting fermentation is not the right move.

• If fermentation is already complete
• If the wine has been stabilized with Campden tablets
• If the wine tastes balanced and stable

In these cases, it’s better to leave the wine as is.

Common Causes of Stuck Fermentation

Understanding the cause helps prevent it in the future.

• Temperature too low or too high
• Lack of nutrients
• Weak or stressed yeast
• High alcohol levels

These factors can cause yeast to stop working before fermentation is complete.

You can also review our airlock guide here: airlock comparison guide.

How to Prevent It Next Time

• Keep fermentation temperature stable
• Use yeast nutrient early
• Use reliable yeast
• Monitor progress with a hydrometer

Prevention is always easier than fixing a stuck fermentation.

Final Thoughts

Stuck fermentation is frustrating, but in most cases it can be fixed.

The key is to diagnose the issue and follow a structured approach.

With the right steps, you can restart fermentation and save your batch.