How To Use Fire Pit and Fireplace Glass?

Utilizing Fire Glass and Lava Rock
Table of contents

How To Use Fireplace Glass?

Fire Pit Media is a coverall term for Fire Glass, lava rock, fire logs, and any other type of decorative feature that can be added to your fire pit or fireplace.

Follow our tips below and you can save some money and get great flames in your fire pit or fireplace.

Fireplace glass is available in a large variety of colors, and can be used in both fire pits and fireplaces, both indoors and in outdoor fire pits with any either propane or natural gas.

It is not safe however to use ordinary ‘domestic’ broken glass such as beer or wine bottles, food containers, etc in a fire feature, in fact, it is potentially dangerous, with sharp edges notwithstanding. Good quality fireplace glass does not emit toxic fumes, or smoke nor does it explode.

Some manufacturers do use offer a product produced from recycled glass

Fireplace glass should never be used on a wood-burning fire pit.

Zion Pre Mixed Fire Glass
Zion Pre Mixed Fire Glass

Good quality fireplace glass will last a lifetime under normal conditions and should carry a lifetime warranty. It is also very easy to maintain. Depending on whether you cover your fire pit when not in use, it may only need to be washed once per season. Use a 50/50 mix of water and vinegar to wash it, and then rinse thoroughly, and allow to dry before using.

Before lighting your fire pit, remove any debris that may have accumulated in the fire pit tray before lighting.

We’ve put together this quick guide so you can easily calculate how much fireplace glass you will need, and how to use fireplace glass in your fire feature. People are often surprised at how much they will need and the added expense to their fire pit project. So to begin this guide we will show you how you can easily reduce the amount of media you need.

How To Use Fireplace Glass

What Size Should I Use?

The vast majority of fireplace glass purchased falls into the 1/4″ or 1/2″ category. But what does that actually mean and how should you choose?

These irregular-sized ‘chips’ of glass are initially produced from a large plate of tempered glass that is smashed into pieces. So the only consistent dimension is the thickness of the original plate of glass, and that is most commonly 1/4″ or 1/2″ thick.

There is no technical issue to use one size or the other it is really only about aesthetics. In a large fire pit, 1/4″ fire glass may look a little overwhelmed, and conversely in a small fireplace 1/2″ fire glass may look a little chunky.

American Fireglass indicate the relative size of their glass as follows:

Image Showing Comparison Of 1/4 and 1/2 Inch Fire Glass


How Much Do I Need?

Many people are surprised to learn that gas coming out of a fire pit burner should not immediately ignite adjacent to the burner. The gas should percolate up through the fire pit media and ignite just as it reaches the top of the fireplace glass/lava rock, which could be up to 2″ or more above the burner!

To reduce the amount of fireplace glass you may need you can use a ‘filler’ from the base of the fire pit tray up to just above the level of the burner. Depending on the manufacturer of the burner/tray that may be about an inch in depth. This could reduce the amount of fireplace glass you need by almost half!

How To Use Fire Pit Glass and Lava Rock as a filler

For most cases, we recommended using small-sized lava rock as your filler ( 1/4 – 1/2 inch ).

Let’s take as an example a 12-inch square fire pit tray which is 2 inches deep and the burner stands up just under one inch above the base of the tray.

The glass should, at the very least be flush with the top of the tray.

Using our Fire Glass Calculator we are first going to calculate how much lava rock we need to just cover the burner. We have measured the height of the burner and seen that 1″ will be enough to cover it. So enter 12 inches in the calculator for both length and width of the fire pit, and enter 1 inch as the depth of fire glass. ( see screenshot below )

Fire Glass Calculator Example

The result is 8 pounds.

However this is the result for Fire Glass, and we are doing this calculation for the Lava Rock filler. Lava Rock has twice the volume-to-weight ratio when compared to Fire Glass. So if we need 8 lbs of Fire Glass then we will only need half of that for Lava Rock 4 lbs. We now know that we need about 4 lbs of Lava Rock as the filler.

Calculating how much fire glass you need to put on top of the Lava Rock will depend on the depth of the tray you are using. For example, a typical tray is about 2″ deep and we have already filled it up to 1 inch with the filler to cover the burner. Therefore we know that we need a minimum depth of fire glass of 1 inch to fill the tray, more if you wish to build up the fire glass level.

The calculation for the quantity of glass required will, therefore, be 12 x 12 x 1 inch, which is the same calculation as we did for the lava rock, only this time we do not halve it, so the result will be that you need 8 lbs of fire glass.

In total, in this example, you would need about 4 lbs of Lava Rock and 8 lbs of Fire Glass to fill this 12 x 12 Tray.

( If for example the tray was 3 inches deep and 1 inch was the height to cover the burner, then the first calculation would remain the same, but for the second calculation you would be entering 2 inches into the calculator for the glass depth )

This method of using small lava rock works well for most colors of glass, however, if you are using a ‘clear’ glass then there is a risk that the lava rock color beneath it will to some degree show through and spoil the purity of color. In this case, we would recommend using a ‘clear’ colored fire bead as the filler but you won’t save as much as using the lava rock.

Different manufacturers have slightly different recommendations about the quantities required, and how they should be used. The figures above are according to the recommendations from American Fire Glass which are probably the leading manufacturer in the US. Below are the recommendations from Firegear Outdoors another leading manufacturer in the industry.

fire glass quantities chart

 how to use lava rock as a filler

At The Magic Of Fire, we only offer our customers the highest quality fire glass that has a Lifetime Warranty. Every order no matter how small is Shipped Free on the US mainland.

If you need any assistance calculating how much glass you may need, please do not hesitate to contact us on our Toll-Free Advice Line at 866 244 9982. Alternatively, use the chat line on any page of the website.

See what Wikipedia has to say about Fire Pit Glass