a deep-fry thermometer; a small spray bottle or atomizer
Slice the potatoes by hand as thinly as possible, about 1/8 to 1/16 inch thick. Pat dry with paper towels. Put the vinegar in a small spray bottle or atomizer; set aside.
Add about one-quarter of the potato slices to the hot oil and fry, mixing constantly with a spider or large slotted metal spoon, until golden brown all over, about 10 minutes. Transfer the chips to a paper towel-lined baking sheet and top with a generous sprinkling of salt. Fry the remaining potatoes in 3 more batches, making sure to return the oil to 300 degrees F between batches.
Spritz a fine mist of vinegar all over the chips and serve immediately (you may not use all of the vinegar).