Sourdough

I once managed to create viable sourdough from flour, sugar and water.   Since then I have failed every time.   A few weeks ago I made sourdough from left over pizza dough, mashed into warm water with a bit of extra flour and sugar.  Next time I tied it didn't work.  So I tried again this week - saving some dough from a loaf, mixing in warm water and flour and making sure it was a fairly thick paste, rather than too watery.  This worked brilliantly and the following day I had a fantastic bubbling mix.  I topped it up with another cup of flour and a cup of warm water.  Another day and I divided it, made a loaf of bread, very good sourdough, with it. Now I have another loaf about to go in the oven, and then a further mix.   It's quite good making bread by the sponge method.  You start with the sludgy sour dough mix - add some more warm water and flour and leave it for a bit.,   Then add a further quantity of flour(s), seeds and salt and knead, etc. as normal.