Stir 60 g (1/2 cup) whole wheat flour and 60 g (1/4 cup) warm water together in a large jar with a fork, then cover the jar and leave it at about 70 to 75 F for 24 hours. The mixture should look like a thick paste with no dry flour pockets.

Check the surface for small bubbles, stir the starter once or twice if desired, then cover it and leave it for another 24 hours. A light stir brings air through the paste, but the starter may still look quiet.

On day 3, remove and discard 60 g of starter, then mix in 60 g (1/2 cup) all-purpose flour and 60 g (1/4 cup) water with a fork. Scrape the jar walls clean, cover it, and leave it in a warm spot for 24 hours.

On day 4, remove and discard 90 g of starter before stirring in 60 g (1/2 cup) all-purpose flour and 60 g (1/4 cup) water. Mix until smooth, clean down the sides, cover, and rest it in warmth for 24 hours.

On day 5, remove and discard 105 g of starter, then blend in 60 g (1/2 cup) all-purpose flour and 60 g (1/4 cup) water. Cover the smooth mixture and allow it to sit in a warm spot for 24 hours.

On day 6, remove and discard 112 g of starter, then thoroughly stir in 60 g (1/2 cup) all-purpose flour and 60 g (1/4 cup) water. Wipe down the jar, cover it, and let it rest somewhere warm for 24 hours.

On day 7, remove and discard 116.25 g of starter, then combine the remainder with 60 g (1/2 cup) all-purpose flour and 60 g (1/4 cup) water. The starter should gradually become lighter, bubblier, and easier to stir after its warm 24-hour rest.

Feed the starter as usual and watch for it to double with abundant bubbles and a springy, marshmallow-like interior, then perform the float test. Move it to a clean jar if desired once the surface is rounded and the sides show an airy network of bubbles.