/ Home & Energy

Could you be damaging the glass of your oven door?

Oven door

You have to be unlucky for your oven door to shatter out of the blue. But if it does, it’s memorable – and not in a good way. While finding the root cause can be tricky, there are ways to lower the likelihood of this happening to you…

A few months ago we asked you to contact us if you’d experienced your oven door shattering.

An interesting discussion on Which? Conversation kicked off, where many of you told us about your experiences of shattering doors.

Since then, we’ve spoken to experts from the Centre for Glass Research at the University of Sheffield who have given us the low-down on exactly how strengthened glass is made, why it can shatter and the difficulties of pinning down the precise cause.

Oven doors

Ovens doors are made from tempered glass, which is stronger than normal glass. Its compressed outer surface makes it less likely to break, but if it does, pieces of glass can fly out onto your kitchen floor.

Fortunately, the individual pieces have blunt edges, so are less likely to cause a severe cut than normal glass.

The only way to be sure of the cause of failure is for the glass to undergo fractographic analysis. But this requires all the broken pieces to be gathered up to enable reconstruction. In the average home, this is next to impossible to do.

What can you do to avoid it happening to you?

Well for starters, we found that 65% of Which? members who clean their oven doors by hand use a scourer. Scrubbing at glass with something abrasive such as a scourer is tempting, especially if you have stubborn cooking grime to banish. But scouring is best avoided as it introduces microscopic scratches in the glass which can cause it to fail spontaneously some time later.

Other easy things to steer clear of is letting the door slam shut, or bash into the metal shelves. And if your door opens horizontally, it can be convenient to place a dish there, but this can compromise the glass, leaving it more vulnerable to shattering.

What to do if it happens to you

If your oven door does shatter and the appliance is out of warranty, don’t bank on a sympathetic response.

Worst-case scenarios from Which? members included long waits, pricey repairs and manufacturer apathy, though occasionally a manufacturer stepped up to the mark and supplied a quick repair free of charge.

We are continuing to push manufacturers to give a consistent and helpful response, so please tell us if your oven door has shattered and what happened next.

Has your oven door shattered? What did you do? How do you clean the glass on your oven door?


Much appreciated.

Useful science which I hope Which? will provide more often in theses sorts of cases. The horizontal glass surface is an interesting insight, and I have in the past used 0000 grade wire wool on glass as it is one of its recommended uses. Did Which? pose this question?

As I complete the annual[?] survey on major appliances what were the results from the 2015 one on shattered oven door glass?

That sort of information may provide a feel for how uncommon it is, or perhaps highlight a manufacturer. Anyway please can we have the survey information as when I complete them I do expect Which? to use the results fully.


Thanks for this follow-up Conversation, Jane.

When I was at school, I witnessed a Duralex drinking glass explode in front of me when it was on a shelf. I discovered that toughened glass can fail in this way when scratched or knocked. Since then, I have been wary of glass breakage. My approach is to do my best to try to protect doors from spatter and if this does happen to clean them as soon as they have cooled using detergent on a cleaning pad intended for non-stick pans.


Normal soda lime glass is not good at resisting sudden temperature changes – such as dropping cold liquid on a hot door. Nor is it good at resisting impact. The toughening process puts the outside surfaces into tension and makes it much more resistant in these respects. Hence its usefulness in many applications, like ovens If the surface “skin” is damaged – the edge nicked, the surface scratched for example , energy is released and the glass crazes in small pieces with safe edges. Remember what happened to older cars’ windscreens. I am surprised that they “explode” in the way described by some; normally when we tested toughened glass panels, by using a centre punch and hammer, they crazed but stayed intact, a bit like a jigsaw.

An alternative would be to use a low expansion glass to resist thermal shock, but it would need to be thicker to resist impact. Borosilicate (“Pyrex”) is commonly used, particularly where the product is not flat.

I hope this kind of excellent introduction will be repeated, where expert input is used.

I’d be interested to know just how many people have problems with shattering oven doors. This will give an idea of the size of any problem. Which? Connect is a survey group with over 30 000 members. They could be asked (I don’t remember if they have)
1. Do you have a freestanding or built-in oven with glass door(s)?
2. Has any of the glass suddenly shattered?
3. If it did break, did it stay more or less in situ or did it “explode” across the kitchen?
4. What make is your oven?

They could, in fact, ask all their members the same question through their magazine.


Borosilicate glass will indeed withstand thermal shock – for example putting a cold casserole on a hot oven door. Having had a considerable amount of specialist glassware made from borosilicate glass at work, I believe that it is the best choice for oven doors.

I presume that the reason that toughened glass sometimes remains in place and sometimes explodes results from differences in the tempering (heat treatment) used in different applications.

It would be interesting to know which type of glass different manufacturers use for their oven doors.


Sorry; correction – the outside surfaces are put into compressive stress.


More statistically based information here:

“The Results.
The answer to a) above … The total number of jobs that have been undertaken by those 97 who responded to the survey was 295,334.
On average, those who responded have been an OVENU franchisee for six and a half years. Many have traded successfully for over 10 years.
Therefore, if we divide the total number of jobs done by the length of time as a franchisee, this shows that, on average, there were 45,436 jobs completed every year.
In answering b)… there were a total of 209 incidents where an oven door glass was broken. As a percentage, this is a reasonably tiny 0.07%. Put another way just 7 breakages for every 10,000 jobs undertaken…..or one every 1,428 jobs … that’s just less than 32 a year out of an average of 45,436 completed jobs.
Leading on to the answer to c)… 152 breakages of the 209 total were accidentally caused by the franchisees. Again, as a percentage, this works out to be just over 72% of all the instances where a breakage occurred.
This leaves just 57 instances out of 295,334 completed jobs where oven door glass shattered for no apparent reason. This figure is just under 9 cases a year.
As a percentage, the 57 ‘mystery’ cases represent just 0.02% … again, put in a slightly different way, a solitary ONE instance per 5,000 jobs undertaken.

And the possible causes seem very interesting commencing with production:


Patrick, thank you! This is surely the kind of information Which? should be including in its reports and Convos so we can see things ino perspective? Do they not have the resources or the expertise to dig out such information or do they choose not to as it might spoil the headlines? They could ask their Members to help of course.

I think it is misleading to withhold useful information like this, and would like the way topics are presented to be much more balanced.


The whole report makes interesting reading: https://www.ovenu.co.uk/shattered-oven-door-glass-survey/

Toughened glass will ensure that there are no large shards to cause injury if breakage occurs, but the shock of an explosion could result in a user dropping food at extremely high temperature.

I wonder whether some manufacturers opt for borosilicate (e.g. Pyrex) glass or if there is a standard that demands use of toughened glass.


The safety standard is BS EN 60335-2-6. It specifies a test for the glass, whether curved or flat, and whether loose or held in a frame. The test requires the use of a specified punch and hammer that is used to break a test panel; it requires that if the panel is loose, the number of crack free particles within a 50mmx50mm square number not less than 60. If the glass is held within a frame, it requires that none of the glass shall become released or dropped from their normal position. A thermal shock test is also specified.

This seems to include borosilicate or similar glass as well as toughened glass, providing they pass the tests.


Thanks Malcolm. This makes it clear that on breakage, the glass is intended to remain in place, so any door that exploded sending fragments of glass round the room is clearly non-compliant with the standard.

I do not know if borosilicate glass can be toughened by heat or chemical treatment. In scientific glassblowing using borosilicate glass it is normal to anneal glass (heating it to between the glass transition temperature and the deformation temperature followed by slow cooling) to remove stresses to reduce risk of cracking in use.


The glass that is held in a frame is intended to remain in place when broken. So borosilicate say, that breaks into large shards must comply.

Boroslicate can be toughened but as it is a low expansion glass I don’t believe it will have the same characteristics as the higher-expansion soda lime.

I have never seen a toughened glass panel “explode” across a space. We used them widely, they are used a lot in larger window and door glazing, in car windows and used to be in windscreens. Whenever they broke or were broken they stayed in place, rather like a jigsaw. So “exploding” would not, in my experience, be normal. It would be interesting if Which? asked Sheffield University to comment on this.


I have seen broken toughened glass windows in cars and doors and the glass has either remained in position or mostly so. I have not seen a broken oven or washing machine door.

It would certainly be interesting to have more input from Sheffield, and Which? has already made contact here.

My experience as a schoolboy made it very clear that toughened glass can occasionally explode and I doubt that all the photos that can be turned up with a simple web search have been contrived.