As a firecrafter I’m always thinking of ways to generate a fire for emergency needs such as heat, signaling, and cooking. Some fire methods are primitive and some are modern. I often look for what resources are available and what can be used without conventional matches or lighters.
I have written an article entitled “Spring Equinox – Optical Firecrafts’ Friend” which shows some of the devices that I have used to start an optical fire. While shopping for groceries awhile back I happened to see a vinegar bottle on a shelf and I noticed the spherical shape of the jar that was filled with clear white vinegar. Recognizing the optical character of this vessel I had to take it hope to have some fun with the sun.
Most liquid filled bottles or jars have some air at the top inside as was the case with this bottle so I elevated the neck of the bottle in order to capture the air and pointed it away from the sun to keep it from interfering with the concave properties of the spherical body.
As with all optical methods, tinder is a critical component of the process so I always look for dry dark fibrous material that I have flattened to create a flat surface upon which the light rays can focus. I often give the tinder a slight orbital rotation to generate a larger spot of heat. When you see embers forming, a direct gentle breath is used to increase it’s size until it is big enough to blow into a flame.
In this case I placed my materials on the back bumper of my car at a convenient height to get things started. Of course you will want to gather your fire lay materials ahead of time so that once you have a flame you can apply it to your campfire.