The Custom Pan Burner on Natural Gas utilizes only secondary air for combustion, that is, there is no air mixer that mixes air with the gas before ignition.   The burner relies solely on the air that is drawn into the flame to complete combustion. The longer the burner is operating, the yellower the flame will become, especially after one hour or longer.

Blue flame indicates that a lot of air is being drawn into the flame.  A fireplace that draws very well will provide more air to the burner and result in a bluer flame.  Also, all of the gaps between the FireBalls draw air into the combustion.  To gain more yellow, you need to "choke" off the air at the burner between the FireBalls.  We recommend the following:

1. Place a layer of ember material on the sand.
2. Place the first layer of FireBalls on the embers.  Fill in the gaps between the balls with the ember material.  
3. Place the second layer of FireBalls and, again, fill in the gaps with ember material.  
4. Continue on this path until satisfied.

There is no other action that will yellow-up the flame other than to restrict the air available to the flame.

Please be aware that a yellower flame will result in more soot being deposited on the FireBalls than with a bluer flame.

To remove most of the soot, at the end of the evening’s use of the FireBalls, when they are very hot, spray the sooty area with water from a spray bottle. The soot dislodges and goes up the chimney. Repeat as needed. You may not be able to get them back to looking as they did when new, but this will help. Do this at the end of each burning to have them remain looking good until the next time they are used.