I am trying to make a sourdough bread with least effort. My receipe is as follows: Add sourdough starter, rye flour, salt and water, mix. Put in a iron tin and wait for 24 Hours for the sourdough to do its work. Bake it.

To avoid that the bread sticks to the iron tin, I lay out the tin with baking paper. I have 2 tins, one with coating and one without. In the tin without coating, the bread gets ugly black spots, and I wonder how to avoid this. I found out that the spots are tasting of metal, so I am pretty sure now that the metal makes the spots, and not burning baking paper.

I especially wonder if the baking paper and tin combination is playing a role here. I know that the sour PH of the dough can corrode baking tins, but I thought that this would not matter when using baking paper.

Here are the black spots Bread with black spots

Here is how i prepared the pan Baking tin with baking paper inside

The other bread turned out ok (same oven, same time) Bread that is ok

  • 1
    Have you thought about seasoning the tin until it's black (like cast iron pans)? That way it would have a coating that probably wouldn't interact so much with dough/moisture.
    – Luciano
    Dec 8, 2022 at 9:24

1 Answer 1


I do something similar but use reusable non stick sheet. Mine is rated to 250°C and I use it up to 240°.

My loaf tin is plated steel, and looks very similar to yours. I suspect your baking paper isn't fully waterproof over the rising time, and is allowing the acidic water from the dough to react with the metal.

You might find that simply double lining the tin is enough. You could experiment with foil under the baking paper, or even wiping cooking oil over the inside of the tin before putting the paper in.

  • It's interesting that the logo is so clear in the black stain on the paper. I wonder if there's some damage to the tin in certain spots
    – Chris H
    Dec 8, 2022 at 6:48
  • Yup, that's rust. Changing to glass or silicone pans would sort that, at the risk of spending a small amount of money.
    – Ecnerwal
    Dec 8, 2022 at 14:46
  • 1
    @Ecnerwal silicone might be OK, but if you prove in the tin, as both I and the OP do (in my case in the fridge, as I have to prepare one evening and bake the next), glass has too low thermal conductivity and too high specific heat capacity, i.e. it will take ages to come up to temperature, even if it doesn't crack first. I prefer a rigid tin over silicone for anything with a bit of weight, but a baking sheet would get round any handling issues.
    – Chris H
    Dec 8, 2022 at 15:11
  • I will definitely try putting more baking paper and the tip with seasoning the tin or putting oil between baking paper and tin. I will report if the next batch is sucessfull. I tried oil before, but it was absorbed during the long rising time.
    – Paul Weber
    Dec 12, 2022 at 13:55
  • 1
    Oh, sorry for the misunderstanding - I used the oil without baking paper.
    – Paul Weber
    Dec 22, 2022 at 7:14

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