Keeping your sourdough starter alive seems to be the thing that takes new sourdough bakers the longest to master. There's a good reason for that - I think it takes people a while to grasp the fact that sourdough starter is actually alive, not just flour and water. As such, it has its own rhythms and requirements, and it doesn't always conform to our own.
I'm working on the premis that you've managed to get some life into your own starter, and that you've read the articles in this website (the recipe '7 day sourdough starter' is probably the most comprehensive, but navigate around the site and you'll find more information of a general nature as well).
There is a problem with any 'recipe' to do with starter. For a recipe, you need exact measurements and consistent temperatures. For a living thing which you want to try to control so that you can use it, this approach, of weights and measures and times, has to be discarded. I'm just going to give you some concepts and ratios so you can understand what you're doing, and with practice you'll 'get it'.
Yes, there may be failures as you learn what works and what doesn't, but isn't that just how life is? The good thing is, even a failure with starter can be easily redeemed by pouring off half (or more if necessary), feeding, and putting away till it comes back. So don't worry, or give up!
FEEDING YOUR SOURDOUGH STARTER
Whatever volume you have established for your starter, it needs to be relative to what you use and when you use it. For example, if you make bread once a week, and you make two loaves of one kilo each, you will need to maintain about twice the volume of starter in your 'mother'. Using typical recipes and ratios, this would equate to roughly 600g of starter all up. Thus, you will use 300g at a time, and refresh with 300g.
But that's just an example, and might not apply to you and your usage. So here are some rules of thumb to help you control your starter, and get the best results from it when you use it.
By way of terminology, the 'mother' is the home base for your starter. It's the place where all your dough comes from, and must be looked after according to some of the following rules. Always remember your mother...
Once a starter has become properly established, and by this I mean it has been fed and used multiple times, keep it in a plastic container in the fridge, especially if you won't be making bread every day. The container should not be airtight, but should have a lid. Don't use a cloth, as the starter will crust, and it is hard to deal with a crust. If you have a tight fitting lid, either pierce it with a knife, or don't clip it on tightly. You want some air, even a tiny amount, to keep it living. Starter breathes !
Plan ahead as to when you want to use the starter. Ideally, it should be at a sponged state when you use it, though a recently collapsed sponge will also be fine.
The longer it is between uses, the thicker you should make the mixture. If it's going to be a few weeks or more before you will use the starter, make it like a dough. You will find that you can even cut off a chunk of the dough you have just made (before the salt is added) and store it in the fridge for a couple of months. It will gradually become more liquid as the bacteria eat up the carbohydrate, so when you come to use it, it will resemble a very sticky batter.
If it has been a while between uses, refresh your starter with just a little flour and water the day before you want to use it in a recipe. This will just kick it back to life, and your bread won't be too acidic.
If you use your starter every day, or frequently, refresh with a smaller amount by volume of the mother. By this, I mean if you refresh with only a third of the total volume of the starter, it will be ready for use more quickly. Likewise, if you double the volume of the mother in a feed, it will take longer to ripen again.
Wholemeal flours soak up more water than white, so my general ratio of one to one will have a thicker texture. A starter which has been established on wholemeal can be swung over to white and visa versa. You just have to feed it a few times with the desired flour and it will adapt accordingly.
Different grains do different things in your starter. I will go into this in more detail on the site over time. For now, wheat flour, rye flour and spelt flour are the simplest to establish and keep. The most sourdough friendly flour is rye flour, which adds a whole new dimension to the flavour of sourdough, and is one of my favourites.
Starter doesn't really die. It just starves, and looks like it has died. If the water has separated out of it, usually this can be poured off, and the remaining starter can be fed with a bit of flour, a little water and your starter will return to life. It will take a while to get happy and productive again, but the characyeristics of your individual sourdough starter will return very quickly. If it has gone mouldy with neglect, shame on you! But you can save your mother, just scrape off the mould and give her a feed.
Too liquid a consistency will become acidic very quickly. This is fine if you use and replenish your starter a number of times a day, but generally it is better to mix to the consistency of a thick batter when using starter frequently. It will become thinner over a short period of time as it eats into the carbohydrate anyway.
On the other hand, a really doughy starter is perfect if you only bake occasionally, and will keep with very little feeding at all. I will progressively add more about this method over time, because I think most sourdough bakers learn the hard way and struggle to keep it simple.
Another great way to keep sourdough starter is using the dough starter technique. This involves progressively thickening the texture of the sourdough culture until it's almost rock solid. Keeps very well, and imparts an amazingly sour flavour to the bread, which somehow also tastes really sweet!
If you more than double the volume in your mother after a feed, you may find that it becomes too alkali. This will inhibit helpful bacteria, but the yeasts will thrive. Your starter's delicate acid/alkali balance will become out of whack. This can later swing to becoming too acid - you will smell vinegar rather than alcohol. It can be stabilised by small feeds over a number of days.
If you have to use starter due to a 'revival' process and you don't want to have it take over your house or fridge, it makes a great base for pancakes, sourdough biscuits, or can be used while still inactive as a part of regular yeasted bread. Adjust your recipe to use less yeast than usual and it will make lovely flavoured yeasted bread. I will put more up on the site about this over time as well.
Keep your starter alive and well and it will work hard to make you look like the excellent sourdough baker you aspire to be!
Sometimes, no amount of maintenance can fully repair the starter - or at least, that's how it feels. Of course, all starters can be repaired, but if you want to just buy some fresh, 30 year old starter, you can follow the link to our School of Sourdough website. Simply order online - as long as you are in Australia, the freight is free!
Overseas orders can't be supplied, due to varying quarantine complexities. Sorry!