First of all I want to say hello to everyone - this looks like a great forum for baking boffins ;)
I'm an experienced baker but new to sourdough, I baked my first loaf the other day. I used a stoneground organic rye for the starter which I used the full hydration technique for 9 days until it was doubling in size. The starter was bubbly and light, not runny and smelled lovely and fruity.
I then used a strong white flour for the dough. 100g of starter and 390g of flour as per my recipe. I got a good sweat on kneading it until it was the right elasticity.The first proving it doubled in size in 4 hours and had a strong structure, I knocked it back and left it for 5 hours in the basket on the second proving. It doubled in size again, but when I transferred it to my cast iron pot for baking it started to sink before my eyes. A sad moment! I baked it and it came out ok- the taste was great and we enjoyed it, but didn't have that lovely open texture it should have had.
I use a heat mat at 30c for proving when I bake as my kitchen is very cold. Always works for other breads I make.. but is this too warm for sourdough? Or was the second proving too long? Sorry I didn't take any pics for evidence!
I'm making a second attempt in a few days, any thoughts would be greatly appreciated :)