Having a sourdough starter is like having a baby. You name it, feed it, clean it and hope you don't accidentally kill it. This is my newest sourdough baby. He's called Nick after my housemate, and is only a few days old now.
Here he is from the top, nice and bubbly, an hour or so after his most recent feeding.
I've had to make a few of these now as I move around a lot and sadly my previous starters haven't always made it with me (R.I.P Derek), so I've got a new one brewing ready to make a loaf in time for bread week on Great British Bake Off.
For those who don't know, a sourdough starter is essentially a living organism, a combination of wild lactobacillaceae and yeast. As they ferment by breaking down the flour, they form a build up of lactic acid which makes the starter sour, giving breads their characteristic tang.
Sourdough can be made the good old fashioned way, just with flour and water, and it should work absolutely fine, with naturally occurring yeasts making their way in from the surroundings. However, if you want to see results a bit earlier, you can cheat and add some yeast straight in from the start and end up with the same result.
Flour - Up to you! For my current sourdough I'm using wholemeal flour, but it works just as well with others - my most recent starter was a 50/50 mix of plain and rye flour. NB if you are going to use plain flour, try to use non-bleached as bleached flour is less bio-active.
Water - warm water (not hot!) is best to speed up the process without killing off the yeast.
7g Dry active yeast
In a clean mason jar, combine 200ml warm water with the yeast, then add 200g flour and mix. Shut the lid, but not too tight, and leave in a warm place.
For the following 6 days you will need to feed your starter daily. To do this, pour out and discard about half of the contents, then add 100g flour and 100g water, then mix. Leave in a warm place.
After those 6 additional feeds, your starter is good to go! If you want to use it on the daily, you can leave it out on the counter, but if you need to wait a bit longer you can store it in the fridge.
I like to wait about 3 hours after its most recent feeding before cooking with it, so the yeast and bacteria are nice and bubbly and active.
If your starter begins to develop a grayish layer of water at the top, don't worry about it, just either tip it out or mix it in if there's not a lot of it. All it means is that your sourdough-baby needs some more food.
As a side note, I can neither confirm nor deny whether it helps make a better loaf of bread, but I would absolutely recommend giving your sourdough a face.