Why Has the Glass Cracked on My Woodburner?

Has the stove cracked on your woodburner? If so, you're probably wondering why it's happened and how you can stop it happening again.

In this article, we'll explore the top reasons for cracked glass on a logburner, tips for avoiding cracked stove glass, and a step-by-step guide to replacing cracked glass on your stove.

So, why has the stove glass cracked on your woodburner?

Reasons for cracked glass on wood burning stove

There are several reasons why glass cracks on a wood-burning stove. But all of the many reasons can be separated into two main causes:

• Impact
• Usage

Let’s look at both of those reasons for cracked woodburner glass in more detail.

Impact

As you might have guessed, impact damage to your stove glass is caused by something coming into contact with your glass more forcefully than it should.

Keep in mind that, even though you might not see the crack straight away, it is possible that the glass is weakened or that a hairline crack that is not yet visible to the naked eye has been caused. Once the stove is operating at a high temperature, the crack might worsen.

The most common examples of this are:

Overloading the firebox

Stove glass often cracks when too much fuel is added to the firebox and the door is inadvertently closed onto a protruding log.

Hitting the glass from the outside 

Banging the hoover into the stove or dropping/throwing something that hits the glass is another common reason for cracked stove glass.

Over-tightening screws and bolts

Having the screws or bolt that hold the glass in place too tight can cause problems. An overtightened screw can cause the glass to crack, especially once the stove is up to temperature and the glass expands slightly.

Contact with a cold liquid

Spilling a cold liquid on hot stove glass can cause the stove glass to crack. The sudden cooling cause by a spilt drink 

Usage

Cracks that are caused by usage or, perhaps more accurately, misusage are those that are the result of how the stove was being operated.

Some of the main causes of misusage causing stove glass to crack are:

Overfiring

This is when the stove is being operated at too hot a temperature. This could be because there is too much fuel in the stove or because too much oxygen is being allowed into the firebox.

Ironically, once the glass is cracked, extra oxygen inevitably gets into the stove, which causes even more overfiring. That’s why it is important to replace your stove glass when you first notice a crack.

Burning household coal

Standard household coal is fine to burn on open fires, but it is quite a volatile fuel. Within the confined space of a stove, this can lead to mini-explosions, which are forceful enough to crack the glass. Find out more about why you shouldn't burn household coal on a woodburner.

Burning pet coke

Burning petroleum-based fuels – whether deliberately or because your fuel supply has because mixed with pet coke – is also likely to cause explosions in the firebox than will cause the stove glass to break.

Avoiding cracked stove glass

The best way to ensure you don’t crack the glass on your wood-burning stove is to take care when adding fuel, only burn the amount and only burn the types of fuel recommended in your stove manual.

To minimise the chances of your logburner glass cracking:

• Don't burn fuel with a high sulphur content, such as pet coke.
• Avoid burning wet or unseasoned wood.
• Avoid slumbering or allowing your stove to smoulder on a low burn for an extended period.
• Check the maximum log length recommended by the stove manufacturer and stick to this.
• Take care not to overtighten the screws holding your stove glass.
• Avoid slumbering when your stove is allowed to burn low for an extended period.
• Replace stove rope at the same time as replacing stove glass.
• Consider using a fire guard to avoid impact.

If the glass on your stove is currently cracked, the good news is that it is relatively inexpensive and quite easy to replace.

How to replace cracked glass on a wood-burning stove

Is the glass cracked in the door of your wood-burning stove?

If you've noticed the glass cracked on your woodburner, there’s no need to go to the expense of buying a new wood-burning stove. Instead you just need to replace the glass.

The important thing is that you do something: the glass is coping with the extreme temperatures that your stove generates. If you spot any breaks, holes or cracks, then the glass will be weakened. It’s best to replace it as soon as possible rather than risk the whole thing shattering one day.

How to replace wood burner glass

Replacing wood-burning stove glass is a very easy DIY task. If the glass is cracked on your woodburner, you just need to follow these simple steps to get your stove up and running once again.

1. Clean the door. The inside of the stove door is likely to be covered in ash and dirt, so it’s worth brushing it down before you go any further.

2. Remove the door. This is not essential, but it’s usually easy to do and, if it’s possible on your appliance, it will make replacing the glass far more straightforward. Removing the door is usually as simple as lifting it off its hinges, but consult your stove’s manual to confirm the best way of doing this for your appliance.

3. Place the door face down. Bear in mind that the surface is likely to get dirty despite your best efforts to clean the door. With that in mind, put a sheet down or work on a surface that you're happy to get a bit grubby.

4. Release the glass. Again, the way to do this varies between different stoves, but you will usually find a metal catch that is screwed or bolted to the door. Simply loosen these – either by moving the catch to the side or, if necessary, undoing the screw or bolt – to allow the glass to be removed. These catches have to be fairly sturdy to hold the glass in place. With soot and tar deposits from using your stove, you might find they are a bit tough to loosen. In this instance, a drop of WD40 and the help of a pair of pliers should do the trick.

5. Carefully remove the glass. As you start to loosen the catches, remember that the glass may come free at any point. Take particular care with the cracked section of the glass.

6. Check the stove rope. The seal between the glass and the door is usually formed by stove rope. This might have become broken or frayed over time. If so, you'll need some replacement stove glass rope.

7. Fit the new glass. Place the replacement stove glass on the door on top of the fire rope. Then move the catches back into place, tightening any screws or bolt that you loosened during the removal process. Be careful not to over-tighten though, as this could cause a crack in your new glass.

8. Replace the door. With the new stove glass in place, put the door back on its hinges. Your woodburner will now be ready to use.

Buy new wood-burning stove glass

If you need to replace the glass on your wood-burning stove, you'll find a wide range of stove glass spares in our store.

Find replacement glass for your woodburner now.