Why Your Fireplace Glass is Turning Black (And How To Prevent It)

A few friends and family have had problems with the glass on their wood-burning stoves starting to turn black. I did some research to try and find reasons why the glass was turning black, what they can do to prevent it and how to efficiently clean the glass.

I thought I’d share what I’ve learnt regarding fireplace glass turning black.

So why does the glass on your fireplace turn black?

Blackened or cloudy fireplace glass is caused a buildup of soot and other small particles on the glass as a result of the fuel in the fireplace not burning properly, or a lack of ventilation over the inside of the glass. One of the main causes of fuel not burning properly is an irregular fuel to air ratio within your fireplace, and a lack of ventilation can be due to air vents that are either blocked or not fully open.

It can be a nuisance having to clean your fireplace glass in order to fully enjoy the fire, so I’ve outlined what can be done to prevent blackening or discoloration of your fireplace, and the top tips for cleaning your fireplace glass.

Reasons Your Fireplace Glass is Turning Black

It can be normal to see some soot or cloudiness in your fireplace after periods of prolonged use, but there are a few things that can increase the buildup of soot leading to your fireplace glass turning black.

An irregular ratio between fuel and air in your fireplace will have an effect on how well the fire burns the type of fuel.

When a fire doesn’t burn the fuel efficiently, it can release small particles and soot, increasing the blackening of glass in fireplaces.

Gas and Propane Fireplaces

Within gas and propane fireplaces, the logs are carefully positioned around the burner ports to allow the fuel to burn as efficiently as possible.

Over time, the burner ports may get clogged up from use, or the logs may get moved.

If these logs are out of place or the burner ports are clogged, it may result in an imbalance between the fuel and air and lead to a buildup of soot developing on both the logs and the fireplace doors.

Wood-burning Fireplaces

Soot can especially be a problem when burning wood. Choosing the right logs can dramatically reduce of soot buildup in your fireplace.

Be sure to use dry and well-seasoned logs that have low moisture content. When burning logs with higher moisture content, more energy is wasted on evaporation than burning leading to an excess of smoke being produced and increased deposits of soot.

Therefore try to use logs with a moisture content of 20% or less.

Check how easy it is to wipe the dirt of the glass. If you find that it’s hard to clean off then the blackening or cloudiness is probably being caused by the logs. If you find that it’s quite easy to wipe away then you’re most likely looking at lack of ventilation within the stove.

It may be the case that your wood-burning stove is becoming outdated, and it might be worth considering investing into a newer appliance.

Most modern stoves have built-in airwash technology that uses a specially designed vent at the top of the stove to draw in air over the fireplace glass to prevent it from going cloudy or black.

Lastly, try to position your wood fires away from the glass panels, as flames too close to the glass can cause black stains that will be difficult to remove.

How to Prevent Soot on Your Gas or Propane Fireplace Glass

Ensure that the logs in your gas or propane fireplace are correctly positioned to the manufacturer’s recommendations, and aren’t obstructing either the supply of air or the supply of fuel to your fireplace.

Clean any soot that may have accumulated on the logs.

Clean the burner ports to the manufacturers specifications.

Ensure that there are no obstructions for air getting into your fireplace. Check your air vents or air shutters.

Check your chimney or flue. It may be the case that there’s a buildup of soot and it’s affecting the ability to draw air from the fireplace. You can read more information here for signs that your chimney or flue needs cleaning.

Have your fireplace inspected and serviced by a professional.

Provide plenty of ventilation for the room.

Check the manufacturer’s recommendations for your appliance to make sure that you’re following the right procedures, including breaking it in.

How to Prevent Soot on Your Wood-Burning Stove Glass

Use dry and well-seasoned logs to maintain your fire. These logs will allow for a more efficient burning process, therefore reducing the potential for soot to be released by the fire.

Use hardwood logs over softer woods such as pine, which have higher sap content. Not only do hardwoods burn more efficiently, they also produce a higher heat output.

Add the logs to the fireplace at a regular rate. Don’t pack the fireplace with a number of logs at any one time as this can smother the flames and prevent the logs from burning properly.

Ensure that your chimney and/or flue have been cleaned within the last year. A buildup of soot can reduce its efficiency at remove further smoke and soot from your fireplace. We’ve put together the most common signs that your chimney or flue requires sweeping.

Have your wood-burning stove inspected and serviced by a professional.

Ensure that the airwash vent is open when the fireplace is in use.

If you have a large stove, be sure to have larger fires to allow the airwash functionality to function properly, but don’t overfill your stove!

Ensure plenty of ventilation within the room.

Check the manufacturer’s recommendations for your stove to make sure that you are following all of the right procedures, including breaking it in.

Position fires away from glass to prevent difficult-to-clean stains forming due to the proximity of the flames.

Tips for Cleaning Fireplace Glass

Just like with an oven, it’s important to keep on top of your fireplace and clean the glass periodically so that a deep clean won’t be necessary further down the line.

Here’s a few top tips for cleaning the glass on your fireplace:

Use a wet paper towel and dip it in the cold ash found at bottom of burner.
Clean the glass in a small circular motion, making your away across the pane of glass. The ash helps to scrub away the soot and dirt.
Leave the glass to dry before wiping any excess particles down with a dry cloth or piece of newspaper.
Don’t use a sharp instrument to scrape away the as this can scratch the glass

Depending on how severe the blackening or staining of the glass in your fireplace, you may want to invest in more proprietary glass cleaning equipment such as oven cleaner.