Feeding your starter
There are five main factors that you control in how you maintain your starter.

1. Ratio of starter:flour:water (by weight)
The amount of starter (as a percentage of the new starter weight can vary from 5-50%.
Some examples of feeding regimens for a starter size of ~120g. All assume 100% hydration:
5% feed:
6g starter : 57g flour : 57g water
20% feed:
24g starter : 48g flour : 48g water
33.3% feed
40g starter : 40g flour : 40g water
50% feed:
60g starter : 30g flour: 30g water
The lower the % of starter, the less acidic (sour) the starter will be. Using low %s of starter is also known as “sweetening the starter”.
Since flour is the starter’s food source – it is easy to see that the ratio of flour to starter increases significantly as the starter % decreases.
At 5% the ratio is 9.5 to 1. At 50% the ratio is only 0.5 to 1. The starter will have 10x the food supply with a 5% feeding vs a 50% feeding. It will go much longer between feedings. It will also ferment more slowly as the yeast and bacteria populations are significantly reduced with respect to the overall starter.

2. Hydration level
A starter can vary in hydration between 50-200%. The hydration level will directly affect what you should expect to see after feeding. 100% is likely the most common hydration (equal weights of flour and water). If the starter is at 100% it lower hydration and is being fed with a wheat flour, the starter will have a gluten structure (just like any other bread dough). The starter will go through a lull period and then begin to rise. It will increase in volume until it reaches a peak. The increase in volume is partially based on the starter’s health – but mostly indicates the gluten strength of the flour being used during feeding. It will hold a peak for some time (longer for higher gluten flours) and if left – will eventually collapse. For higher hydrations, the gluten will not be strong enough to trap the gas produced – the starter will not increase in volume – but will have a period of active bubbles rising to the top and popping. This activity will eventually slow.
Higher hydrations will:
Ferment faster
Run out of food sooner
Produce lactic acids rather than acetic acids

3. Temperature
Temperature can be varied from 40f to 85f. It is not advisable to go over 85f. Under 40f – fermentation will almost cease.the most balanced fermentation (yeast and bacteria) will occur in a narrow band of about 74f – 78f. Over 80f, the starter will favor bacterial activity and lactic acid production. Under 70f, it will again favor the bacteria and acetic acid production. Enzyme activity, yeast and bacterial fermentation directly correlate to temp. Warmer = faster / Cooler = slower.
The fridge really just puts everything in Slow motion.

4. Type of flour
Flours will hydrate and ferment differently
Flours in order of starter activity (greatest to least)
While grain Rye
Whole grain Wheat
Unbleached flour
Bleached flour

Just to note – treated municipal water supplies may negatively impact the starter.
Personally, I would avoid bleached flours

5. Frequency of feedings
At room temperature, a starter can be fed from 1-3x a day. The higher the hydration, temperature and flour activity, the more quickly the starter will exhaust it’s food. A 100% or lower hydration fed with 33% starter or less and kept at 70f should easily go 24 hours between feedings.

In the fridge – it should only need to be fed once per week. To maximize time between feedings – change the hydration to 50%, feed with only 10% starter and unbleached flour. Refrigerate after feeding and it will last 2-3 weeks between feedings in the fridge.

A starter can change hydrations at any feeding. It can also change size at each feeding (up or down).

The best size starter you can keep is one that most closely matches how you use it.
Each feeding will require some % of starter to be removed. This is referred to as the discard. Ideally you use it to bake or
make other SD items.

The best time to use a starter:
For less sour breads – as it is peaking or early in the peak
For more sour breads – end of the peak or as starter is collapsing

A really generic feeding is 1:1:1 or equal weights of starter : flour : water.

The most common mistake made is to believe that feeding equal measures of flour and water is a 100% hydration starter.
Since hydration is weight based, you need to consider the different weights of flour and water.
1C of water weighs 236g
1C of flour weighs ~132g
Feeding equal measures results in a hydration of 178.7% (236/132) – not 100%.
It will bubble – not double in size.

Happy feeding.