The Fresh Loaf

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MAKE rusbrot CLAS (24h); FLAS (48h); TH-SD w_ solod (24h); SERGEY'S 4 Day clas.

jo_en's picture

MAKE rusbrot CLAS (24h); FLAS (48h); TH-SD w_ solod (24h); SERGEY'S 4 Day clas.

Clas, flas and TH-SD are types of sourdough (Type II) used with small amounts of dry instant yeast (DIY) to make bread (often in 4-5 hours).

Refer to the detailed instructions by rusbrot for

  • clas here (0:42-6:00);
  • flas, rusbot's  MALT KMKZ, here;
  • TH-SD hereTH-SD stands for thermophilic sourdough.  



To make clas/flas, just mix the ingredients below and place in a jar.

     Obtain malt grain(rye or wheat) from a hobby brewing supplies store.

Both clas and flas can be maintained in a water bath in a crockpot with a temperature controller.

Try to match the level of the water bath with the level of the jar contents (clas or flas).

Note that rusbrot emphasizes the use of plastic film on the surface of clas to inhibit mold growth. 

This is not needed for flas since the liquidy contents of the jar may be shaken up a couple of times a day. 



(Note that a water bath might be maintained in a proofer also. ) 

Using clas/flas

Strain out the grain sediments in flas mixture; flas (for use in bread dough) is the liquid portion that is left.

Both clas and flas can be used immediately. 

Refrigerate clas for 1-2 days and use as if fresh; flas can refrigerated for a week or more.


FREEZE portions of clas(120g)/flas(90 gr) for later use.  You will have sourdough at your fingertips!!


(See below for THERMOS Method.)


Refresh rye CLAS  rus brot -

-No need to add vinegar or use a plastic film to cover surface of clas mixture.

General Proportion: (#gr rye in clas) : (new rye flour)  = 1:9

Recipe: Mix the following and ferment at 38-41C , 12 hrs.

29 g Clas (10 g rye, 19 gr water) - room temp

90 g whole rye flour (preferably freshly milled)

171 g(ml) water (45C)

Hydration: 190%   Yield: 290 g rye clas


********  Proportions for Refreshment in 6-8 hr: (#gr rye in clas) : (# gr new rye flour)  = 1:2    Recipe: 29 g Clas; 20 g whole rye flour; 38 g(ml) water;    Yield: 87 gr clas    




Wheat Clas  (24-36h)

RecipeMix the following and ferment at 38±2C, 24-36 hrs.

-Use plastic film on surface of wheat clas mixture during fermentation.  Ending pH-4.

25 g whole grain wheat malt flour  (buy malt grain from a brewing supplies store)

75 g whole grain wheat flour

10 g(ml) vinegar (5% acidity)

140 g(ml) water (45C)

Hydration: 150%   Yield: 250 g wheat clas


Refresh wheat CLAS  (12 hrs)

-No need to add vinegar or use a plastic film to cover surface of clas mixture.

General Proportion: (#gr wheat in clas) : (#gr new wheat flour)  = 1:7

RecipeMix the following and ferment at 38±2C, 12 hrs.

30 g wheat Clas (12 g wheat, 18 gr water) - room temp

84 g whole wheat flour (preferably freshly milled)

126 g(ml) water (45C)

Hydration: 150%   Yield: 240 g wheat clas



Thermophilic Sourdough Starter with fermented rye malt (solod)

Refer to ingredients and procedure by rusbrot. Makes 250 gr.

  • 40 g crushed unfermented rye malt
  • 10-15 gr fermented red malt (solod)
  • 200 ml water at 60C       400% hydr  (200:50)   | rye  | H2| H2| H2O | H2O |

Ferment: 24-30 hr; 50-53C (use a water bath); shake or stir mixture periodically.

 Result:  flavor like apple/plum



Recipes by rusbrot using thermophilic sd starter-




SERGEY's 4 Day Clas


The recipe for Sergey's clas is at foodgeek (see also his Live Journal article).

It is a 4-5 day process.

To refresh takes 24 hrs at 40C.

Mix 50 gr clas with 180 gr ground rye and 270 gr water at 42C.

Hold it in a water with a temperature controller at 40-42C.

(You can also use a proofer.)

It may take 48-60 hr to get the plum fragrance and the reddish tinge.

See the crumb for 100% lean whole wheat loaf here.





In the lean 100% whole wheat loaf baked in the Zojirushi in a 2000ml Pullman pan, the following amounts were used.

Range for rye flour from above sourdoughs:

   clas: 8% (above table)-12%;  for Predough-3%

   flas 18.9% (above)-28%

   TH-SD: 5% (above)




THERMOS METHOD for making a "modified clas"- the hydration is 300% (cp to 190% in rusbrot formulas).


  • Warm a thermos with 50C water for 15 min. Empty it.
  • Pour 290 ml of 45C water and 10 ml of vinegar into thermos.
  • Use a funnel to add rye flours (75g whole rye and 25 gr wh wheat malt, both freshly ground).
  • Close thermos and shake vigorously to mix flour and water-no lumps.
  • (Optional- Set thermos in an ice chest with a large jar of boiling water.)
  • Shake the thermos about every 8 hr.
  • Check for pH < 4 in 24 h.

Keep in mind that the hydration of this "clas" is 300%.     | rye  | H2| H2| H2O |

If a recipe of 500g total flour contains 10% rye flour from clas (50 gr), then 200 gr of "modified clas" is needed to supply 50 gr. rye;  the liquid supplied is 150 gr.  Adjust total hydration accordingly.


A refresh using the thermos would only require 12 hr. 



Ilya Flyamer's picture
Ilya Flyamer

Do you find any difference in performance between CLAS and FLAS?

jo_en's picture

I am doing tests now. They are pretty close.

A very important factor was  20 gr freshly ground wheat malt for both kinds of loaves (added to 455 gr red hard wheat).

That made both of them comparable.

Flas with wheat malt (4.2%) in a whole grain loaf is completely satisfactory to me. (Same for clas.)

It is liquid so its use in a recipe only requires a liquid change.

With clas, it takes a quick adjustment for the extra flour in the clas to keep 80% hydration.


But I am doing practically all loaves baked in the  Zojirushi. 

I have to pay attention to the final rise and it is slightly different for clas. 

There is one area I want need to test: Which one stales faster.

It seems eating unfrozen bread within 2-3 days is preferable to freezing for us.

Finally, when making flas, I discard (now in the garden) the spent grains. With clas,

all the flour is used. It feels like a bit of waste with flas.  Freezing with both make it super convenient.


What do you think?

Have you tried the thermophilic sd (at 65C,48h)? I am wondering if it can be used like flas in wh wheat bread, but will give better flavors.

Ilya Flyamer's picture
Ilya Flyamer

Nice, thank you for the info! I've never used FLAS, so can't say much. I do like using CLAS on occasion, when I need bread fast and don't have time to make it using my regular starter.

I'd guess you can use the spent FLAS grains in bread by the way.

Never tried thermophilic SD unfortunately, and now I don't have a way to maintain 65C for a long time :( rus brot has a video where he uses up leftover thermophilic starter and makes white wheat bread with it: (it's in Russian, but the description looks very google-translatable). Please share your results if you try it!

jo_en's picture

Thank you for the reference! -- it may have just what I was looking for. 
Would you resend the link? I think it is mis-typed.

Wed I will start a 65C batch of rusbrot's thermophilic. I also am reading the article at



Ilya Flyamer's picture
Ilya Flyamer

Fixed the link, sorry!

Nice article :)

jo_en's picture


For maintaining 65C:

Have you thought of using a thermos and a thermo insulated bag?

With thermos alone, I could just keep 43C over 24 h / flas and 40C for clas (4-5 degr drop at end) in a thermos- room at 68F. They both seemed to perform very well though the temp was a tiny bit low.

For thermophilic and cla/flas I am going to try putting the thermos in a  small insulated zip bag and maybe with a very hot water bottle next to it. I am guessing it must help improve the last 2-3 degree temp drop.

jo_en's picture


Have you seen this use of spent grains back in bread dough?

jo_en's picture


Yippee's picture

Thanks for putting it together!