Can Fire REALLY Melt Glass?

You learned through our last article that fire can melt most types of metal if the flame is hot enough. Now you’re curious about another seemingly impervious material, and that’s glass. Can fire melt glass?

Fire can melt glass, however, glass has a melting point of only 2,552 to 2,912 degrees Fahrenheit. This means most sources of fire will not burn hot enough to reach that point. Interestingly, glass will only melt, it will not burn. That’s because glass is not combustible or flammable so it can’t oxidize.

In today’s article, we’ll talk further about what it takes to melt glass. Make sure you keep reading, as we have lots of great information to share! 

What Is the Melting Point of Glass?

Glass is comprised of sand that’s heated to about 3,090 degrees. The sand, which is typically silica or silicon dioxide, becomes less crystalline as it’s exposed to heat. 

When the sand eventually cools, its structure changes, lingering somewhere between solid and liquid. That makes the resulting product–which is glass–an amorphous solid. 

The melting point of glass is, as mentioned in the intro, somewhere between 2,552 and 2,912 degrees. If you read our post on metal melting points, then you’ll realize that glass has a moderately high melting point, but not overly high. 

Can Fire Melt Glass?

So, that naturally brings us to the question, can fire melt glass?

Well, in our post about fire melting metal, we listed the max temperatures that different types of flames burned at. Let’s now revisit those flame temperatures to determine which can melt glass and which cannot.

These Flame Sources Can Melt Glass

  • Oxyacetylene: The heat generated by oxy-fuel cutting is upwards of 6,000 degrees. Thus, oxyacetylene can melt glass several times over.
  • Acetylene: An acetylene blowtorch has what it takes to cut through metal. Its hottest flame temperature is 4,172 degrees, which is plenty warm enough to melt glass.
  • Hydrogen torch: If you’re using a hydrogen torch, you could rely on this tool for melting glass. The flames from the torch max out at about 3,632 degrees. 
  • Propane blowtorch: If not a hydrogen torch, then a torch powered by propane could get the job done. A propane torch reaches temps between 2,192 and 3,092 degrees, which can melt glass if on the higher end of the temperature spectrum. 

These Flame Sources Cannot Melt Glass

  • Candle flame: Candle flames can get hotter than most people expect, burning at about 2,012 degrees. Even the hot spots can get as warm as 2,372 to 2,552 degrees. The upper temperature limit of a candle flame is the lowest melting point of glass, so a candle couldn’t melt glass.
  • Bunsen burner flame: At their hottest, Bunsen burner flames are 2,912 degrees. At that temp, a Bunsen burner could melt glass. However, when operating at a lower temperature range of 1,652 degrees, the glass would remain intact.
  • Methane: It’s a similar story when starting a fire from the natural gas methane. At its highest flame temperature, which is 2,732 degrees, glass would melt. If methane only burns at 1,652 degrees though, then it’s not sufficient.
  • Charcoal fire: If you’re hoping a charcoal fire could melt glass, you’ll be disappointed. Charcoal flames burn at 1,382 to 2,192 degrees, which simply isn’t hot enough to liquefy glass.
  • Butane: A butane fire only burns at 600 degrees max since low gravity causes the flames to be cooler. That’s far from enough heat to melt glass, so the surface would remain intact.
  • Methanol: Methyl alcohol flames burn at 2,192 degrees max, which is hot, but it’s about 400 degrees lesser than what the glass melting point is. 
  • Wood: A wood-burning fire smells nice, but it too won’t put a dent in glass. The flames burn at 1,880.6 degrees, which falls too short.
  • Gasoline: Gasoline barely burns any hotter, as the flames are 1,878.8 degrees on average. You know what that means, you can’t use gas flames to melt glass.  
  • Kerosene: The oil kerosene also hits temperatures under 2,000 degrees, burning at its hottest at approximately 1,814 degrees. A kerosene fire wouldn’t leave glass a melted mess. 
  • Animal fat: Should you burn animal fat, the resultant fire will reach top temperatures between 1,472 and 1,652 degrees. That’s almost 1,000 degrees under the threshold that glass needs to melt. 

Can Fire Burn Glass?

We’ve established now that some sources of fire can melt glass, causing it to drip if the fire is hot enough. Will glass ever outright burn though?

Fire can not burn glass. Glass isn’t a combustible surface, and it’s not flammable either. That means it can’t oxidize. 

Fire needs oxidation to occur, and as it does, hydrogen and oxygen atoms mix with carbon to produce water and carbon dioxide. 

Interestingly, when rust develops on metal, it’s this same form of oxidation at play.

We digress though. 

You’ll recall that silicon dioxide or silica burns to make glass. Once it’s exposed to such high temperatures, the silica cannot burn further. 

Glass can still look charred if it’s exposed to high heat, but that’s from the carbon that forms when other nearby flammable objects oxidize.  

Most sources of fire can melt glass if the flames surpass at least 2,550 degrees. However, glass doesn’t burn since it isn’t flammable or combustible. 

Even still, melting glass can be highly injurious, so be safe! If your home or building is burning, call 911 immediately.