Blown vs. Brown malt

27 Dec

Blown malt left, Brown #1 on right

Diastatic brown malt is a dark malt kilned over a fire fueled with coal, wood or straw which has enough diastatic power to convert itself. Made during a time before the widespread use of thermometers and hydrometers the colours and level of diastatic power would have varied between maltsters. An essential source of information on malts of this time comes from the London and Country Brewer by William Ellis published in 1736.

Times for kilning malts is described as being either 4, 6 or 12 hours with the “pale sort” requiring “more leisure and less fire than the amber or brown sorts”  But is it really that simple?

In my previous attempts to make diastatic brown malt a couple of years ago I didn’t think I was successful in answering the question that has been bugging me since the first time I read the London and Country Brewer and that is; how was malt dried in 4 hours with high heat, able to maintain some diastatic power, since enzymes are destroyed very rapidly over 221°F.

Modern brown malt is kilned at a high temperature, 350°F from it’s green stage, right after germination. It will not have any diastatic power.

We do know that brown malt did not have the same diastatic power as pale from the description of kilning brown malt.   “…is often crusted and burnt, that the farinous part losses a great deal of it’s essential Salts and vital Property, which frequently deceives it’s ignorant brewer, that hopes to draw as much Drink from a quarter of this, as he does from pale or amber sorts” (pg.14). What we don’t know are the kilning temperatures.

Some 70 years after this publication a study of brewing industry practices was carried out to determine if Bere barley grown in Scotland should be taxed at the same rate as English barley. The Scotch Bigg Report (Thomas, Coventry and Hope)  presented to the British Parliament in 1806 contains some of the earliest empirical data on brewing and malting collected on a large scale and includes kilning temperatures. This report also pre-dates the development of Black Patent malt (1817). Malts were still referred to at this time as either pale, amber and brown. What I found very surprising in this report is that a temperature of 170°F is given for brown malt which is the same curing temperature for pale malt.  “Malt may be made brown at a lower temperature for it is not so much the temperature, as the suddenness with which it raised, while the malt is still moist, which alters the colour.” Pg. 33 However, they also recorded some maltsters kilning at temperatures of 186°F and suspected some kilned as high as 212°F.

So how does it get dark?   With Munich malt temperatures are raised while there is 20-25% moisture in the malt causing a partial caramelization and it is more highly modified which encourages melanoidin formation upon kilning making a darker malt. It’s also kilned at a higher temperature as well but even Aromatic malt is not as dark as I would imagine a porter being at the time. In my experiments trying to make brumalt I somewhat accidentally achieved a very dark malt by stewing the malt in the proteolytic temperature range of 44-59°C or 113-138°F. So I looked for some clues to see if there was something in the older methods of malting that would promote more Maillard reactions, perhaps if using traditional methods the malt would darken to a greater degree.

One major difference between malting today and back then is the use of continuous un-aerated steeping. In another blog post I tested the theory of un-aerated steeping and it’s effect on slowing the growth of barley and it certainly does, The reason germination times were so long is because of this and to some degree the cooler temperatures. Aerated steeping is a relatively new development (150 years) in the malting industry and was utilized successfully or more consistently due to the development of pneumatic malting. This subject is probably worthy of a book so I’ll stop right here. So in order to mimic the old malting methods I would need to use a continuous steep. There is a theory that because a continuous steep delays chitting that the barley absorbs water more consistently. With aerated steeps the grain usually starts to chit before the last steep. This may cause water to absorb faster at the embryo end as opposed to along the entire length of the endosperm, so the same amount of water may be absorbed but with one end being slightly drier and therefore may affect modification. Chitting during steeping can also cause over steeping which can lead to uncontrolled growth and high malting loss. (Briggs Malts and Malting p.123)

One clue to another difference is in the London and Country Brewer with the mention of a couching phase at the end of germination; “When it is at this degree and fit for the Kiln, (wilted or when “the Root begins to be dead”) it is often practised to put it into a Heap and let it lye twelve Hours before it is turned, to heat and mellow, which will much improve the malt if it is done with moderation and after that time it must be turned every 6 hours during twenty-four.” This is actually very similar to the method used to make Brumalt or Melanoidin malt. The malt is covered and allowed to heat up to 50°C 122°F for 36 hours, only it is not turned and the carbon dioxide eventually stops the growth, but the effect is the formation of reducing sugars and amino acids. Interestingly I found this description in Brewing and Distillation by Thomas and Stewart 1848 “It was formerly the custom in Scotland to pile up the whole grain into a pretty thick heap, and allow it to remain for some time. The consequence is the evolution of a very considerable heat, while at the same time the malt becomes exceedingly sweet.” They go on to say that this is no longer practiced because of malting loss and that “the very same change takes place afterwards in the mash tun, without any loss whatsoever.” 

Lastly, I recently bought a copy of La Practique du Maltage Lucien Levy 1898 and there is a kilning schedule for “Malt Anglais” which states. “It rises as fast as possible to 50 ° (malt temperature and not air). We stay there for about twelve hours.” (Translated from French) It then goes up to 60 for another 12 hours. Interesting! lots of time for proteolytic enzyme activity here especially if it raised to 50° with a high moisture content. However this is not mentioned in the Scotch Bigg report but it does say that kilning takes anywhere from 40-80 hours and that the starting temperature is usually the same as body temperature which is 37°C. With such long kilnings it wouldn’t surprise me that the malt would spend a considerable amount of that time leading up to 50°C and that there would be a lot of enzyme activity during this initial kilning.

I suspected a “hot couch” and some stewing at 50-60°C would definitely add some colour but would it be enough at a kilning temperature under 212°F This will be malt #1

Just to be sure I also planned to make a traditional malt with the hot couch but without the proteolytic stew and just go straight to 205°F for 4 hours. I know with such a high moisture content going this high right away would be bad for the diastatic power but I was more curious to see what effect this would have on colour. This will be malt #2

Blown malt, malt #3

Blown malt on the left, brown on right

In the London and Country Brewer of 1736 a distinction is made between malt that is “blown” and brown malt.

 On the subject of frames, or the materials used for the kiln floor it states “the Iron and Tyled one, were chiefly Invented for drying of brown Malts and saving of Fuel, for these when they come to be thorough hot will make the Corns crack and jump by the Fierceness of their Heat, so that they will be roasted or scorch’d in a little time, and after they are off the Kiln, to plump the Body of the Corn and make it take the Eye, [ What I believe “take the eye” means is that it will simply look better by increasing in volume. In Wigneys 1823 Philosophical Treatise of Malting and Brewing he describes the effect of  sprinkling as “giving to the malt a plump, fair appearance to the eye…” ] Some will sprinkle Water over it that it may meet with better Market. (Malt was sold by volume) But if such malt is not used quickly, it will slacken and lose it’s Spirits to a great Degree, and perhaps in half a year or less may be taken by the Whools (a small insect) and spoiled: Such hasty dryings or scorchings are also apt to bitter the Malt by burning it’s skin, and therefore these Kilns are not so much used now as formerly” This is a criticism of surfaces that conduct or retain too much heat. What he is describing is “blown malt” although he does not refer to it as such. Corns that “crack and jump” and expand in size will occur when temperatures are high and the moisture inside the grain cannot escape fast enough. 

Most recipes for Blown malt after Black Patent malt comes into use refer to it as simply Brown or Porter malt. All the recipes I’ve read dry the malt  to a certain degree first. In Brewing and Distillation by Thomas Thompson and William Stewart (1848)  “Brown or Porter malt is dried by applying the same heat at first as to pale malt, and after it is half dried, by blowing it (as it is termed) on the kiln. This is done by raising the heat as high as the men who turn it on the kiln can possibly stand. This may be stated at 200° for the first turning, and higher afterwards.”  The same thing is stated 50 years later in La Practique Du Maltage: The brown malt or blown is obtained as follows: We take malt half kilned and we carry it in a second kiln heated with a large fire of oak or beech it is installed in layers of 3-4 centimeters.

What also encourages this popping effect is the shrinkage of the pores of the husk which occurs after the “free drying” stage of kilning which happens at around 23% moisture. So if the temperature is raised very rapidly at this point the steam formed will not be able to escape fast enough and the kernel will pop. I suspect the sprinkling of water can increase the malt temperature faster by adding steam to the malt bed. I decided not to try sprinkling water on mine. This time I just wanted to try drying the malt down below 30% and subjecting it to a high heat, above 212°F. I put it in the oven at 350°F which may have been overkill but it sure popped! It sounded sort of like popcorn when it really got going after 20 minutes at this temperature.

Malt #1 Hot couch and 21 hr. stew+ 4 hours at 205-210F

  • Malt #1 Continuous steep until 44% changed water twice
  • 8 day germination. Malt temp. between 11-13°C 52-55°F
  • Hot couch 36 hours in an open cooler to mimic a larger amount of malt. Temp. reached 39°C Turned after 12 hours then every 6.
  • 21 hours kilned lightly covered, closed vents, no fan at around 50°C
  • Moisture now at 28%
  • Kilned for 2 hours at 205*F
  • 2 hours at 210°F


  • Malt #2 Continuous steep until 44%
  • 8 day germination 11-13°C 52-55°F
  • Hot couch 36 hours temp. reached 39°C 102°F
  • kilned for 4 hours at 205°F moisture at 14%
  • kilned another hour and a half  at 205°F moisture down to 6% Colour was light!
  • kilned another 2 and a half hours at 210°F (8 hours total kilning) Colour now at around 30L

Malt #2 Hot couch, no stew and 8 hrs. at 205-210.

  • Malt #3 Blown Malt Same steep

    Blown malt #3

  • same germination
  • same hot couch
  • same limited stewing at 50°C 122°F as malt #1
  • Moisture at 28%
  • Kilned for 40 minutes at 350°F
  • Moisture below 5%

Blown malt #3



Observations: When comparing the Blown malt to malt #1 the colour is almost the same. I was really excited to see how dark #1 got. Much darker than my previous attempts at Brown malt. Because malt #2 remained light, even after 8 hours kilning,  it’s safe to attribute the darkness in colour in malt #1 to the limited stewing phase at 50°C. I ran them all through a mini-mash at 152°F pH adjusted to 5.2 (or as close as possible with a little baking soda or some acid malt) for one hour. I was not using the standardized congress mash, instead, I was using a scaled down version as if I were brewing a 5 gallon batch with 10lb of malt only I was using 4 oz of malt. The math may have gone a little sideways but as long as it was the same for each I thought it would make an interesting comparison.  Of course #1 had the highest brix at 9° and the blown had the lowest at 7°. I was pretty surprised to see that Malt #2 had some diastatic power at 8°. As a control I made another mini-mash the same way with a pale malt and it also scored a 9°.

Mash #2 which did not have the initial lower temperature kilning remained a gloopy mass and the mash did not separate from the wort. This was not surprising as the beta glucans had not been broken down which may show the importance of the enzyme activity during kilning below 50°C 122°F or more specifically in the 37-45°C 98-113°F range .

Malt #2 after mashing notice the lack of separation of wort.

Malt #2 after 5 1/2 hours kilning at 205°F and still light.


The flavour of the Blown was bitter and slightly charry like a roasted malt. The interior of some of the kernals was charred while the exterior looked a nice light brown with some darker areas. Malt #1 tasted great nice and malty. As for volume the malt was divided by weight before kilning. After kilning Malt #1 measured 4 1/2 cups. The Blown was 5 cups, a difference of 10% Perhaps it would have been more had I sprayed some water on it during kilning.


I know I’ll get a lot of people questioning my methods here they’re not the most scientific, but I think it answered some questions in my mind about the effects of using a proteolytic stewing (or a slow kilning) phase. Also I think it’s safe to say that by omitting any initial drying or even withering phase the London and Country Brewer article has an oversimplified version of the kilning process. That may have been obvious to a lot of people but I know it has caused a lot of debate amongst others.

What I’d like to try is kilning at a lower temperature and raising the temperature when the moisture content is lower around 20%. I’ also like to try making a blown malt at 200-250°F which is where I observed some popping happening during my first attempts at brown malt as I think this may be more historically accurate. But first I think I’ll make a much larger batch for a more historically accurate porter and perhaps this time I’ll get to play with some fire!

Many thanks to Melanie and Andrew at McInnes Farms for supplying me with a big sack of Newdale barley grown 10 minutes away from where I live. These experiments and many more to come will be done with this barley.

Mini mashing

Mini sparge


Posted by on December 27, 2017 in blown malt, Brown malt


Tags: , , , , , ,

20 responses to “Blown vs. Brown malt

  1. Marco Battistutta

    December 27, 2017 at 10:35 am

    Hi François! Your experiment seems to confirm two texts which talk about this. One is a graph you posted in an old article where it shows that the optimal taste is achieved with a kiln phase starting around 50°, another (I Don ‘t remember where I read it) is a Japanese study of Sapporo or Asahi where they claimed the best tasting malt is achieved with a final drying phase taken around 50° or even 60° to develop flavour before killing.

    • jfdyment

      December 27, 2017 at 6:02 pm

      Hey Marco, indeed the graph showed that by raising the kilning temperature to 145-155F 62C-68C range at 25-35% moisture content improves flavour but at the expense of diastatic power. What I was trying to show was the effect on colour and if older methods of malting encouraged melanoidin production. From my understanding what’s happening at this range and moisture content is the activation of the enzymes which act on the proteins in the grain breaking them down into smaller amino acids. when these amino acids combine with the sugars produced (with the well modified malt enhanced by the hot couch) and heated you get the Maillard reaction – lots of browning. So once these enzymes are activated they are now spent and our diastatic power is reduced. By playing around with all these factors you can customize your malts – you can add colour, make maltier flavours, or by kilning low and Curing at high temperatures you can get toastier flavours. There are lots of variables to play with!

  2. Demy

    December 27, 2017 at 11:24 pm

    I think the inside of the malt is a complex factory !! While reading the post, I was reflecting on a recipe for dark candi syrup (I personally tried) where they reduce sugars (sucrose break with heat alone, no acids), amino acids (from beer must) and a high pH (it helps a lot the formation of melanoidin), so I think everything is correct and I was thinking about the pH of the water absorbed by the grains, maybe it could partly play a role. I do not know if it might interest you but I blew the barley (not malted) because I saw that it exists commercially (used to replace barley flakes) I started to clean the barley, boiled very briefly in a few minutes (rapid increase in humidity inside) and then put in a pan over low heat (not in the oven). As soon as the grain starts to dry out, it starts to crackle and expands slightly (similar to popcorn but less noticeable). Although we are talking about a different product, I think that high humidity and high heat create that effect, so I think you could try (last heat phase) with a pot more than with the oven …. maybe .. and just a trace!

    • jfdyment

      December 28, 2017 at 2:32 am

      Interesting! So you didn’t soak the barley but just boiled for a few minutes and then the barley had direct contact with a pan? I’ll give it a try, it seems that blowing malt or barley is a bit of an art – (insert rude joke here)

      • Demy

        December 28, 2017 at 4:42 pm

        Yes, cleaning in water as usual then small boiling (about a minute) then in contact with a very hot pan. As soon as the surface water begins to evaporate, I lower the flame and soon after the barley starts to crackle. I have done several experiments and it seems this is the best. The inside of the seed remains white and the outside is golden but cooking can continue. This is a method used by me to make popcorn (but with dry seed, no boiling) without having the appropriate machine. Pultroppo I used what little I did otherwise I would send a picture, I could send a link to a commercial product (it is identical to what I got) but risk of advertising .I could make a video and send it via e-mail if necessary.

      • jfdyment

        January 1, 2018 at 1:13 am

        Hey Demy I just tried this using some raw barley at 14% moisture. I did one with water and one without and it worked for both although I used a very small sample so it was hard to see any difference. There is a line in The Scottish Ale Brewer and Practical Maltster ( WHRoberts) 1847 which quotes A Treatise on Brewing by G.A. Wigney about “blown” malt “This system is much practiced in drying off brown porter malt and the blowing is carried to a greater extent than with pale malt” This is for “increasing volume for profit” so this was done with pale malt as well ! I’m curious to see how much diastatic power is lost by doing this.

  3. Demy

    January 1, 2018 at 6:01 pm

    Hi François, I tried both methods with boiling and without (with raw barley, not malted) and it works both, but the method “boiled” I think that it creates a greater gelatinization (being only starch) before being roasted. After writing this post, I went for a light test of the malt and I worked equally with it (probably it is not necessary to boil being the modified starch). Very interesting ….. I found something here maybe interesting

  4. Demy

    January 5, 2018 at 4:08 pm

    Hello François, I was starting to stew the caramel malt when I thought about putting it in a pan to see the effects. Barley has humidity of 47%, change of 100%. I put the green malt directly in a pan and lit the flame of the gas, at first lively then lowered. After a few minutes a sort of liquefaction began, I think it comes from a high internal humidity (I think the enzymes do not have time to get around, I think), in fact it is not as sweet as in caramelized malt and has started to crackle as well. As soon as it was dried, I removed the roots and then I continued to cook, until I obtained a “chocolate” malt. The malt is incredibly crumbly with a sweet beginning and a dry finish, delicate but less bitter than the corresponding product in the oven. I think cooking in the pan deserves attention: it is less homogeneous than my rotating basket, but also gives different results. I thought I’d share it.

    • jfdyment

      January 5, 2018 at 5:00 pm

      Demy, I was about to update this post because I cut into my blown malt (malt #3) which was highly modified green malt stewed at 50C cooked at 350F (177C) and to my surprise it was glassy! in 80 out of 100 kernals. Which is the same as the last caramel malt I made. Of course they were very dark, some charred but I was expecting to see a lot more starch. Especially since it only spent 40 minutes at 350F. Was this enough to convert the starch to sugar? Or am I seeing something else like cooked gelatinized starch? I’m going to try soaking some raw barley, then boiling it to gelatinize, then cook it and dry it out to see if I get the same glassiness. Perhaps there are different qualities of glassiness and maybe it’s not the best indicator of conversion for caramel malts.

      • Demy

        January 5, 2018 at 5:13 pm

        This is my malt, I hope to see… It is made directly from green malt (100% modification)

  5. jfdyment

    January 5, 2018 at 5:43 pm

    That looks good! Nice colour! I can see a little glassiness in there, about the same amount as the malt #1 that I made. I think you’re right about the frying idea – as stated in the London and Country Brewer- Iron and “tyled” (ceramic) frames were used and although they were perforated would have more of a frying effect on the malt. I’ve been trying to find any pictures of the horse hair cloth that would have been used in kilns but I’ve only found one English company that makes fabric out of horse hair.

    • Demy

      January 5, 2018 at 6:16 pm

      There is a small glassiness, but it is different in caramel malt. Despite being dark it has a limited “burned smell” compared to the oven (I would have said the opposite !!) I think that high humidity plays a key role with the starches and the pan. I tried with a dry malt (melanoidina) but I did not have the same result, I tried with the saccharified green malt to make the crystal (red caramel, say) but the outside of the grain is overcooked (even on low heat) while the interior is still light, perhaps good for a very dark caramel malt. . While I stopped cooking to remove the roots I remembered that the description of some malts (commercial) says “double cooking”, (maybe special b, I can not remember), maybe it’s a stupid question but some heating / cooling cycles have some consequences on malt?

      • jfdyment

        January 5, 2018 at 7:24 pm

        Very interesting. I also read that about Special B, I’ve also read that about Blown malt. I did manage to make a Special B type malt which tasted and looked the same, I have a post about it- I did not “double cook” it but I did stew at 50C for 12-16 hours before the saccharification stew. I suppose cooling the malt would have the effect of not cooking the inside as much, (just a guess) because you’re exposing the outside to more heat than the inside. Worth some more experiments!

      • jfdyment

        January 5, 2018 at 10:07 pm

        Hey Demy just added a link to my new malting log book (top right) which you might find useful, I’ve also added a translate button to the blog as well on the bottom right side.

  6. Demy

    January 12, 2018 at 5:58 pm

    Hi Francois, I’m doing a small batch of melanoidin malt and I was wondering: proteolytic enzymes are active for such a long time? I read somewhere that after a few hours are degraded (during mash), so I’m a bit confused …. I want to do it in the best possible way ….. thanks!

    • jfdyment

      January 12, 2018 at 11:18 pm

      Well most of what I’ve read had a “hot couch” method allowing the grain to rise to 50C in the center. This is stated to take 36 hours, but that depends on the malt and the amount etc. I did this with the brown malt because this method is stated in the 1736 country brewer. I’ve found that to get colour there was a big difference between malt stewed at 50 for 8 hours compared to 16. For a regular melanoidin you don’t have to stew for a long time if at all, just do the 36 hour “hot couch” then dry it.

      • Demy

        January 13, 2018 at 2:45 pm

        I stewed for about 20 hours (50 ° C) to see the results, the smell during cooking is really delicious. I noticed that during the 50 °C stewing the inside of the malt turns yellow and has a peculiar smell. I asked this question because I wondered how long an enzyme can perform its function before denaturing, I know that this depends on the temperature but I always read that enzymes after a few hours of activity are inactivated … from this derives my question. In fact I have not found any scientific information on this, it could be useful for example during the mash for “difficult” malts such as corn.

  7. jfdyment

    January 13, 2018 at 5:21 pm

    It’s an interesting question, I’ll look into it. We’re talking about the physiology of enzymes. How long do they last, when are they spent. Enzymes can continue to be active, however slowly for weeks if the final moisture of your malt is above 6%. Mash conditions are meant to provide the most ideal conditions for the enzymes to work so they will work faster. I’ve been reading about historical kilning schedules in England being 4 days long – 1 day at 38, 1 day at 50 etc. I’m wondering what these malts are like to brew with. a lot of enzymatic activity would occur during these periods.

    • Demy

      January 13, 2018 at 6:29 pm

      I agree, the long times of certain malts make you think ….. it is an interesting and useful discussion both during these (special malts) and during the brewing, it would be interesting to deepen. Thanks for your answer


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