Rye malt grain: 25g

Wholegrain rye flour: 75g

Water at +45C: 180ml

Unflavoured vinegar 5%: 10ml

These are all the ingredients you will need. CLAS has 190% hydration. It is possible to use virtually any malt grain, but according to rus brot rye malt is the most efficient, so let’s stick to his recommendations. The same applies to flour as well, but let’s stick to the recipe which is guaranteed to work.

You might notice vinegar in the recipe. Why do we need it? It will help to set initial acidity of the mix and prevent yeasts and other microorganisms from propagating in our starter in the early stages. It won’t have any effect on bread flavour, so don’t worry about it. Any unflavoured vinegar should work. If you don’t have 5% vinegar, you can use any other concentration, just make sure to adjust vinegar and water contents accordingly. For example, for 9% vinegar you will need 5.5ml of it and 194.5ml of water.

First step would be to mill rye malt grains into coarse flour, but don’t make it too coarse. Then mix everything together in a container and make sure there are no dry bits left.

Cover your starter with a plastic film, sourdough mix should not have any contact with air and evaporation should be avoided as well. Then cover your container with a lid.

Put it somewhere where you can set temperature at +40C. It should not go below +38C and should not rise above +42C. Rus brot is using a yogurt maker, I was using my oven with just a lamp turned on — it managed to stay at exactly +40C for the whole time. Leave it doing its thing for 12 hours.

Give your mix a good stir after 12 hours, cover with fresh film and leave for 12 more hours. Overall fermentation time should be 24 hours, but sometimes it can be fully developed a bit faster. All in all 24 hours should yield the result we’re looking for. If you need video instructions on how to prepare CLAS, take a look at rus brot’s video on YouTube. It’s in Russian, but with English sub-titles. He is making more CLAS there, but proportions are the same and taken from his blog.