I’m always exploring firecraft possibilities and while grocery shopping I noticed a unique bottle containing vinegar. It had a spherical base with a tall cylindrical throat. Because the vinegar was clear, it in effect, became a lens.
This could be a staple in your kitchen that could serve dual purposes, culinary and optical. In fact, when emptied it could be refilled with water or any other clear liquid to renew it’s optical properties.
While my experiment was done in late October it still performed well at the sun’s latitude. I had to catch a trangent opening in the clouds to create an ember.
There are better tools to create fire but this just adds one more way to create a fire in an emergency. Next time that you go shopping you might pick one of these up to experiment with and see if you can create a coal. Keep in mind that a dark material works best as tinder and heats up quicker.