My first impression is that the towel might not be porous enough to let the all-important yeast and bacteria in. Try cheesecloth.

If that doesn't do it, here's the long version:

Creating a Starter:

First and foremost, a week isn't necessarily enough time to get a starter going full steam ahead. It can take as little as a few days or as long as a month. You're relying on ambient yeast and bacteria that are floating around in the air, and the amount of yeast and bacteria available varies according to location, climate conditions, and all sorts of other environmental factors. The specific species and strains of yeast and bacteria also vary from place to place, which is why San Francisco is renowned for its ssourdough - they have the best ambient yeast and bacteria strains. Give it time.

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Maintaining a Starter:

Feeding Schedule:

As a general rule: Once your starter is healthy and active, bubbling, rising vigorously, and smelling sour, you have two options:

1. If you store the starter at room temperature, you need to feed it twice a day. Don't wait for the risen starter to collapse before the next feeding, because it messes with the ph levels and can make the yeast and bacteria less active. Every 12 hours, feed it.

2. If you store the starter in the fridge, you can go up to a week between feedings. The cold won't kill the yeast and bacteria, it just slows them down. Just make sure the starter doesn't get shoved into a super cold spot and freeze.

The feeding process:

Stir the starter, remove all but 4 ounces of it (you can either discard the rest or use it to bake something). To the remaining 4 ounces, add 4 ounces flour and 4 ounces of purified or bottled water (chlorine in tap water is bad for the yeast and bacteria, and most filters remove chlorine taste, but not all the chlorine). Room temperature starter gets room temperature water; refrigerated starter gets lukewarm water. Stir until no dry flour remains. Cover with a non-airtight lid. Refrigerated starters need to stay at room temperature for several hours after feeding so the yeast and bacteria have a chance to wake up and eat.

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I made my starter about a decade ago, so I don't recall the details with absolute clarity. If I recall correctly, I fed the starter every 12 hours for the first week, then every 24 hours for the next week. I went with 50 grams water/flour so there was less waste and tossed half the starter just before feeding. It certainly was not ready for bread making at one week. It was barely ready for making bread at two weeks. It takes time for the wee beasties to take hold. Patience is needed on your part.

After a month or so, my starter would double in a few hours after feeding. After perhaps a few months, maybe six, it would triple or quadruple in a few hours. It takes time for a new starter to establish itself.

If your starter has any activity at all, you want to figure out exactly when it's MOST active and feed it just then. You're looking at a population expansion, so if you feed it at peak activity before it gets a chance to start declining (dying off from lack of food) you'll get it thriving in not time. As someone else mentioned, your starter looks pretty wet, be sure you're feeding it 50% water 50% flour by weight, not volume. Good luck!

I think every 24 hours is too long between feedings if it is a new starter. I have started several and fed them every 12 hours, and before a week was up it would triple aqnd quadruple nicely. One source I read said a wet towel over the top held on with a rubber band will help keep bugs and flies out of it, but you have to spray the towel regularly with water to keep it from drying out. I have better luck just sitting a saucer on top of it.

Sourdough is an ecology of two types of micro-organisms: yeast and lactobacillus. Both are widely present in our environment and will spontaneously "contaminate" the flour you use. If they cohabitate for months, they form a mysterious ecology which is good for both. We call this mystery "Sourdough Starter".

Lactobacillus is what turns milk into yogurt. It reproduces rapidly (20 minute doubling time)

Yeast is what turns starchy solutions into beer. It reproduces slowly (2 hour doubling time)

Yeast has different requirements during its growth phase and stationary phase.

Growth phase is when the starter doubles in size. The yeast cells are in oxygen-consuming metabolism and reproducing. Once the oxygen is used up, yeast switches to stationary phase in which it does not reproduce, but just converts sugar to CO2 and alcohol.

To get a starter going from scratch, you want reproduction! With yeast's long doubling time, you need to give it time. 4 hours may seem like forever, but it is only 2 doublings. A single yeast cell will turn into about 4 cells. However, in 24 hours (12 doublings) it will have formed over 4000 daughter cells.

Once the yeast uses up the oxygen, it switches to anaerobic metabolism and stops reproducing. It produces CO2, so the culture keeps getting bigger even if the yeast is not increasing in number. You can't use the volume of the culture as a measure of the number of yeast cells.

So, rules for starting a sourdough starter:

1. Deliberately contaminate the first batch with a neighbor's starter, a pinch of store-bought yeast or a spoon of yogurt. These initial bugs may not be the long-term inhabitants of your starter, but they will get the ecology started and make you starter more inhabitable by the wild yeast and lactobacillus which will be the ultimate inhabitants.

2. Get air well mixed into the starter. When feeding, add the water first and stir vigorously until the old starter is completely dispersed into the water. Yeast must have oxygen! Brewers bubble oxygen through their wort to get the yeast growing fast.

3. OK, I lied. Yeast doesn't need oxygen. It can use olive oil instead. Put 1/4 tsp olive oil in before mixing.

4. Yeast needs micronutrients as well as flour. 1/4 tsp molasses or brewer's dregs provides these.

5. Yeast can't eat starch. "Sacrilege !!!" I hear someone scream. It's true. The starch needs to be broken down by grain enzymes into simple sugars before yeast can eat it. These enzymes are present in small amounts in white flour, more in whole wheat and much more in malted barley flour ("Malt Flour"). Malt flour will increase the proof of any bread recipe, so you should have some in the kitchen anyway.

Your question asked how often to feed your starter. If you follow the above guidelines, I would recommend every 24 hours for the first week, then go to whatever your long-term breadmaking schedule is.

If you bake every day, feed after making bread and leave it at room temperature. If every two days or longer, feed and put in the fridge. If you have neglected it for more than a week, feed once to "wake it up".