3:1, 1:1, 3:2? What’s the right ratio for burn juice? If you don’t have an opinion on drip mix you must not be very cool. The more adamant you are the more likely you are to talk loud about how everyone else does it wrong – no matter the topic. Wait…what were we talking about? Oh yeah…drip mix. Amanda Stamper shares her view on the matter, and gives us a bit of a history lesson as well.
By Amanda Stamper – Oregon Fire Manager, The Nature Conservancy
A recent podcast about drip torch leg burns got me thinking about drip torch fuel mix ratios. It is no coincidence that I make this association. Last October my pants caught on fire while I was burning gamble oak in New Mexico. After having learned during briefing about how to properly extinguish Nomex on fire by grabbing your pants with a gloved hand and pulling them away from you to extinguish rather than smothering the burning fuel against your skin, and just before my pants combusted, we engaged in lively debate about the proper drip torch mix ratio. And I thought the mix was too cool!
So what is the proper drip torch mix ratio? Does the likelihood of one’s pants catching fire change with different fuel mix ratios? Have you ever wondered how bio-diesel might work in a drip torch? How were burns ignited before the various combustible liquids were at our disposal? These and other questions arise the further one probes.
Ask Ten Fire Managers
Ask ten fire managers from across the country for the ratio of diesel to gasoline in drip torch or slash fuel mix, and you are bound to get at least two if not three or four different answers. Not sure about the ratio of agreement vs disagreement, but suffice to say that drip torch mix ratios depend on the fuels, burning conditions, and perhaps nothing more than past practice of the organization or local area.
Where longevity of combustion is more important than temperature, as in pile burning or broadcast burning for reduction of larger diameter fuels, a higher percentage of diesel may be desired. More diesel than gasoline is perhaps the only cardinal rule when it comes to mix ratio, with somewhere between 3:1 and 4:1 being the most common. The most volatile mixture, according to the U.S. Forest Service, is 3:1, and is recommended for use only in appropriate fuel types (such as grass) during periods of high humidity.
A 5:1 fuel mix ratio is reported to have been used on the Saddle Prescribed Fire, where a burn injury associated with pants igniting occurred in 2012. My pants caught fire with the 4:1 ratio being used on the burn in New Mexico, that I had deemed cool given that I had long been using 3:1. Is longer-burning fuel a contributing factor? Does gasoline vaporize more readily and thereby contribute less to pants igniting? More research to this end may be needed.
More on Bio-Diesel
As for bio-diesel, it works just fine with drip torches and has been utilized in both hand pile burn and broadcast burn situations since early 2006. The Medford District BLM has used over 1,200 gallons of bio-diesel in slash mix during prescribed fire operations to date. The mix is made by using 99% bio-diesel and regular unleaded gasoline in a 3:1 slash fuel mixture. Bio-slash fuel burns similar to regular petroleum diesel/gas mix, but with less toxic wick smoke, with more of a cooking oil smell instead of sulfur or diesel fumes. The liquid is also less toxic for personnel and the environment during mixing and handling. The cost when using the “off road” discount is comparable to diesel #2. Bio-diesel has a solvent effect on the slash tanks and drip torches and seems to prevent sediment build up, as well as a slightly higher flashpoint than regular diesel.
Other Firing Devices
Before flammable liquids were being used in wildland fire operations, fire was ignited using materials largely obtained from the same environment being burned. Among the most notable in North America is the fatwood from longleaf pine, from which the fat lighter used for setting the woods on fire is made. The rich and resinous smell of its smoke only adds to the pleasure of burning.
Fire-stick farming refers to the burning practices of Australian Aboriginals to enhance the productivity of the land., Many wooden matches have been struck and tossed by sheep herders on their way down from the mountains to rejuvenate meadows for grazing. Recreational burners everywhere use lighters if that’s all there is.
Would you feel comfortable throwing matches instead of dot firing? What are some other traditional or unconventional firing devices that we could and should be using?