If you think this is worth it, let me know. I'll put the materials in here, and based on your feedback, I may need to tweak the info a bit by using subsequent posts.
DISCLAIMER: This article deals with modifying a propane-powered heating device. If you are uncomfortable in doing this, consult your local hearth store or a professional.
I have a propane firepit on my deck, much like this one that Home Depot currently sells. (Except mine's about five years old and I got it on a closeout sale at our local hardware store.)
Here's a link, so you know what we're starting with: http://www.homedepot.com/p/UniFlame-...vZc6naZ1z10qmr
This firepit's been mostly OK, but my nephew the glazier said, "Ya know, that lava rock stuff in there doesn't look very cool... The current trend is to have crushed glass, for a Fire from Ice kind of look. I'll get you a sample from our stock."
I must comment here that for this project, you cannot use plain glass, like bottle glass, or anything else EXCEPT tempered glass. ONLY tempered glass can stand the heating/cooling cycles safely.
And on his next visit, he brought me a sheet of Azure Blue glass in a packing box.
The first thing to do was to get the glass to break. I tried a screwdriver and a hammer in the middle of the plate, but no luck. So I asked him what to do. "Tempered glass is really strong across its surface, but weak on the edge. Hit it there." So I put the sheet of glass inside a big tub, stood it on edge, and covered it with a dropcloth. It only took a single blow, and POP, it crumbled into nice cubes.
If you don't have access to this kind of glass, you can buy 'Fireglass' online, for about $30-$40 for ten pounds.
So with the glass ready to go, the next thing is to modify the firepit.
Remove all the lava rock from the firepit and sort it for size. Set aside any pieces that are taller than the burner top. Using the remaining pieces, take the largest that will fit under the burner top, and slide them inside the crown of the burner top, so that you create spaces and voids that the burner can work through Set them tightly together so that they lock together, giving a craggy space underneath the burner top. Fill the bottom of the burner area to below the level of the burner top with the remaining pieces of lava rock.
If you don't do this step, when you pour in the glass, there won't be enough to fill the top of the firepit, and the glass will lock tightly together, making it impossible for the firepit burner to work right.
Put on gloves and pour the glass slowly into the firepit. Pick up any wayward chunks with the gloves. Look for small shards (I found a few in mine) and discard them carefully.
Once the glass is poured into the top of the firepit, (I didn't level mine - it looks better to me this way), open the door where the propane bottle is stored, disconnect and remove the propane bottle temporarily.
Now get some metallic tape - the kind used for sealing chimney ducts - and wrap it around the air intake on the bottom of the burner. Don't stick the two edges together to make a tight seal, but instead leave them apart by an inch or so. This is the starting position.
Re-install the propane bottle and hook it up. Get a blowtorch so that you can start the firepit reliably. Start it in the usual manner, by pushing the valve in.
You should have a pretty good fire in the firepit. Allow the glass to warm up for a few minutes on high, then turn it down most of the way. If the firepit doesn't blow out, then turn it down all the way and watch it. If the firepit blows out, turn off the gas, allow the fumes to clear for a few minutes, and close off a little more of the air supply to the burner. The trick is to have a little bit of air supply but not too much, because your flame front is now in the glass and not in the burner area itself.
And THIS is the result! Here's a daylight shot:
And here's a shot after dusk:
Hope you enjoyed it!