See below for my day-to-day notes on how to develop a sourdough starter from scratch! I have provided a full tutorial for you to follow along (see the video tutorial here and note the timestamps below correspond to the time point in this tutorial). You'll need a couple starter jars with lids, cheesecloth, a spatula (or spoon), a rubber band (optional), unbleached flour, and purified water.Day 1: [timestamp 1:48]Prep flour mix350g bread flour + 150g dark rye = 500g flour totalStir together flour & water into a pasteEqual weight, 1:1 (30g water + 30g flour)Day 2: [timestamp 3:47]Stir paste mixtureTransfer to fresh jarDay 3: [timestamp 4:50]Notes: volume increased, caught wild yeastDiscard all but 20g starter (throw away discard)Stir in fresh flour & waterEqual weight 1:1:1 (20g starter + 20g water + 20g flour)Day 4 morning: [timestamp 6:34]Notes: lots of activity, unpleasant smellBegin 2 feeds per dayDiscard all but 20g starter (throw away discard)Stir in fresh flour & waterEqual weight 1:1:1 (20g each)Day 4 evening: [timestamp 7:45]Notes: lots of activity, very unpleasant smellDiscard all but 15g (throw away discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Day 5 morning: [timestamp 8:41]Notes: loss of all activity! Very unpleasant smell, very runnyDiscard all but 15g (throw away discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Day 5 evening: [timestamp 9:47]Notes: minimal growth, still smelly, very runnyDiscard all but 15g (throw away discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Day 6 morning: [timestamp 10:35]Notes: 20% volume increase (1.2X), smell improving, runnyDiscard all but 15g (throw away discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Day 6 evening: [timestamp 11:21]Notes: 30% volume increase (1.3X), smell is more mild Discard all but 15g (throw away discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Day 7 morning: [timestamp 11:49]Notes: 100% volume increase (2X), smells nice, bit of sour, consistency is less runny, strongerDiscard all but 15g (throw away discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Day 7 evening: [timestamp 13:35]Notes: 50% volume increase (1.5X), nice mild sour smell Discard all but 15g (throw away discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Day 8 morning: [timestamp 14:03]Notes: 90% volume increase (1.9X), smell is very nice Discard all but 15g (*begin to collect and freeze discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Discard cheesecloth, now use a loose-fitting lidDay 8 evening: [timestamp 14:54]Notes: 2X volume increase Discard all but 15g (collect and freeze discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Day 9 morning: [timestamp 15:21]Notes: 2.5X, definite sour notes!Discard all but 15g (collect and freeze discard)Stir in fresh flour & waterEqual weight 1:1:1 (15g each)Day 9 evening: [timestamp 15:50]Notes: 2.5X, lots of activity!Discard all but **8g (collect and freeze discard)Stir in fresh flour & waterBegin 1:2:2 feed (8g starter + 16g water + 16g flour)Day 10 morning: [timestamp 16:40]Notes: starter peaked at 2.5X and then fell/collapsedDiscard all but 8g (collect and freeze discard)Stir in fresh flour & waterFeed at 1:2:2 (8g starter + 16g water + 16g flour)Day 10 evening: [timestamp 17:20]Notes: starter peaked at 2.5X and then fellDiscard all but **5g (collect and freeze discard)Stir in fresh flour & waterBegin 1:3:3 feed (5g starter + 15g water + 15g flour)Day 11 morning: [timestamp 18:00]Notes: starter peaked at 2.5XDiscard all but 5g (collect and freeze discard)Stir in fresh flour & waterBegin 1:4:4 feed (5g starter + 20g water + 20g flour)Day 11 evening: [timestamp 18:26]Notes: starter peaked at 2.5X & fellDiscard all but 5g (collect and freeze discard)Stir in fresh flour & waterBegin 1:5:5 feed (5g starter + 25g water + 25g flour)Day 12 morning: [timestamp 18:53]Notes: starter peaked at 2.5X, smell is wonderful (sweet & sour)Discard all but 5g (collect and freeze discard)Stir in fresh flour & waterBegin 1:5:5 feed (5g starter + 25g water + 25g flour)**Flour mix change: [timestamp 19:20] From 30% rye to 10% rye Math: Total remaining flour weight = 155.5g This means there is still 155.5*0.3=46.5g rye in the mix For 10% rye, we need 46.5g rye in 465g total flour So bring up total flour weight from 155.5g to 465g Added in 309.5g bread flour, whisk wellDay 12 evening: [timestamp 20:23]Notes: starter peaked at 2.5X, peaked & fellDiscard all but 5g (collect and freeze discard)Stir in fresh flour & waterFeed with 10% rye 1:4:4 (5g starter + 20g water + 20g flour)Day 13 morning: [timestamp 21:01]Notes: starter peaked at 2.5X, peaked & fell, stronger discardDiscard all but 5g (collect and freeze discard)Stir in fresh flour & waterBegin 1:5:5 feed with 10% rye (5g starter + 25g water + 25g flour)Day 13 evening: [timestamp 21:38]Notes: starter peaked at 2.5X, wonderful activityDiscard all but 5g (collect and freeze discard)Stir in fresh flour & waterFeed at 1:5:5 (5g starter + 25g water + 25g flour)Day 14 morning: [timestamp 22:15]Notes: starter peaked at 2.5X, will now begin 3x per day feedsDiscard all but 8g (collect and freeze discard)Stir in fresh flour & waterFeed 1:2:2 (8g starter + 16g water + 16g flour)Day 14 afternoon: [timestamp 23:08]Notes: starter peaked at 2.5X, will now begin 3x per day feedsDiscard all but 8g (collect and freeze discard)Stir in fresh flour & waterFeed 1:2:2 (8g starter + 16g water + 16g flour)Day 14 evening: [timestamp 23:34]Notes: starter peaked at 2.5-3X, will now begin 3x per day feedsDiscard all but 5g (collect and freeze discard)Stir in fresh flour & waterFeed 1:5:5 (5g starter + 25g water + 25g flour)***Regularly do this 1:5:5 for the longer, 10 hour overnight feed (did an experiment for the video with 10g + 50g + 50g but usually feed only 5g + 25g+ 25g)