The fuels used in building a fire normally fall into three categories relating to their size and flash point: tinder, kindling, and fuel.
Tinder is any type of small material having a low flash point. It is easily ignited with a minimum of heat, such as from a spark. Tinder must be arranged to allow air (oxygen) between the hair-like, bone-dry fibers. The preparation of tinder for fire is one of the most important parts of firecraft. Dry tinder is so critical that you should keep it available at all times. It may be necessary to have two or three stages of tinder to get the flame to a useful size.
Examples of tinder include:
- The shredded bark from some trees and bushes, such as Cedar, birch bark, or palm fiber.
- Crushed fibers from dead plants.
- Fine, dry wood shavings and straw/grasses.
- Resinous sawdust.
- Very fine pitch wood shavings (resinous wood (Fat Lighter) from pine or sappy conifers).
- Bird or rodent nest linings.
- Seed down (milkweed, cattail, thistle).
- Charred cloth.
- Cotton balls or lint.
- Steel wool.
- Dry powdered sap from the pine tree family (also known as pitch).
- Foam rubber.
Kindling is the next larger stage of fuel material. Kindling should also have a high combustible point. It is added to, or arranged over, the tinder in such a way that it ignites when the flame from the tinder reaches it. Kindling is used to bring the burning temperature up to the point where larger and less combustible fuel material can be used.
Examples of kindling include:
- Dead dry small twigs or plant fibers.
- Dead dry thinly shaved pieces of wood, bamboo, or cane (always split bamboo as sections can explode).
- Coniferous seed cones and needles.
- “Squaw wood” from the underside of coniferous trees; dead, small branches next to the ground sheltered by the upper live part of the tree.
- Pieces of wood removed from the insides of larger pieces.
- Some plastics such as the spoon from an in-flight ration.
- Wood which has been soaked or doused with flammable materials; that is, wax, insect repellent, petroleum fuels, and oil.
- Strips of petroleum gauze from a first aid kit.
- Dry split wood burns readily because it is drier inside. Also the angular portions of the wood burn easier than the bark-covered round pieces because it exposes more surfaces to the flame. The splitting of all fuels will cause them to burn more readily.
Fuel, unlike tinder and kindling, does not have to be kept completely dry as long as the fire is well established to dry the wet fuel prior to burning. It is recommended that all fine materials be protected from moisture to prevent excessive smoke production. (Highly flammable liquids should not be poured on an existing fire. Even a smoldering fire can cause the liquids to explode and cause serious burns).
The type of fuel used will determine the amount of heat and light the fire will produce. Dry split hardwood trees (oak, hickory, ash) are less likely to produce excessive smoke and will usually provide more heat than soft woods. They may also be more difficult to break into usable sizes. Pine and other conifers are fast-burning and produce smoke unless a large flame is maintained. Rotten wood is of little value since it smolders and smokes. The weather plays an important role when selecting fuel. Standing or leaning wood is usually dry inside even if it is raining. In tropical areas, avoid selecting wood from trees that grow in swampy areas or those covered with mosses. Tropical softwoods are not usually a good fuel source. Trial and error is sometimes the best method to determine which fuel is best. After identifying the burning properties of available fuel, a selection can be made of the type needed.
Recommended fuel sources include:
- Dry standing dead wood and dry dead branches (those that snap when broken). Dead wood is easy to split and break. It can be pounded on a rock or wedged between other objects and bent until it breaks.
- The insides of fallen trees and large branches may be dry even if the outside is wet. The heart wood is usually the last to rot.
- As a last resort, green wood which can be made to burn is found almost anywhere, if finely split and mixed evenly with dry dead wood.
- In treeless areas, other natural fuels can be found. Dry grasses can be twisted into bunches. Dead cactus and other plants are available in deserts. Dry peat moss can be found along the surface of undercut stream banks. Dried animal dung, animal fats, and sometimes even coal can be found on the surface. Oil impregnated sand can also be used when available.