Tuesday, May 22, 2012

Making (Diastatic) Brown Malt, Again

The last time I tried my hand at making a historical malt, back in early December, I made a 19th century porter malt. The brown malts produced at this point in time, around 1820-1850, were highly roasted over hornbeam wood and were primarily used for flavoring porter. They were not diastatic - a mistaken post title on my part - and would have been used for somewhere around 15-25% of the total grist. That was then. Moving back in time, the next step in my brown malt quest was to make an actual diastatic brown malt with the methods and ingredients used a hundred years before the darkly roasted stuff. An early to mid-eighteenth century brown malt, kilned over straw, to be used for 100% of a porter grist. The original brown malt.

Figuring out how to create such a thing was not as easy as I had originally thought. For unlike most brewing malts, brown malt has existed in different forms for much of its history. The brown malt of the early 18th century was very much different than the stuff made a hundred years later. The more I began researching the different forms of brown malt, I quickly realized just how murky and complex the history really is. One could write a whole book on brown malt production. Anyways, to get a better sense of the types of brown malt and the context in which it was manufactured, I'd like to deviate a bit and provide a rudimentary historical outline.

-  The early 1700's. Gin is the drink of choice for the drunken masses and Londoners prefer their porter without a smokey flavor. Brown malt is kilned over a number of fuels, including coke, coal, straw, wood, and fern. The first three were considered the best and wood/fern the most smokey. Most of the fuels necessary for malt production were expensive. The famed canal systems of the 19th century were still in their infancy and transportation costs made it prohibitive to kiln malt with coke and coal. At the same time, wide scale deforestation had led to an acute shortage of charcoal the failure of the coppicing system of wood production. Straw kilned malt it was. These were lighter colored brown malts and could be used for 100% of the grist. Color was probably more dark brown than black. Could be consumed relatively young or aged to dissipate smokiness.

-  Mid to late 1700's. Coal production increased and transportation costs fell. Coke kilned pale malts became relatively inexpensive and by the end of the century porters were often brewed with sizable amounts of pale malt - nearly 50% of the grist. Whether or not these brown malts were darker in color or less diastatic as those a few generations before...? Hornbeam, oak, beech, and other hardwoods eventually become an integral part of making brown malt. Beers were aged for years in vats and sent out stale and mild for mixing in pubs.

-  Early 1800's. Hornbeam becomes the wood of choice for brown malt production. Huge coppices of hornbeam in Hertfordshire and Hatfeild supply the massive malting centers of Derby and Ware for the London brewers. (Ware had over 100 maltsters making brown malt by 1800, only 25 by 1855). Supposedly, different forms of brown malt disappear/appear- snapped, blown, brown, and porter malt. Brown malt was expensive and dangerous to make, even though it was made from a lower quality barley than pale malt. (It required a minimum of 8-10 faggots of wood per quarter of malt. Price, 3+ shillings per quarter). Porters brewed from mixtures of pale, brown, amber, and later on black malt. Color dark brown to black.

-  Mid to late 1800's. Brown malt is used primarily as a flavoring agent. Darkly roasted and mixed with pale and black malts. Start of decline of brown malt use in porters, with the exception of London. Expensive to make and not nearly as efficient of a coloring agent as black malt; 30 bushels of brown malt equal 1 of black in color.

Ok, still with me?

The first thing I had to do to make my batch of diastatic - straw kilned - brown malt, was to find a way to kiln the stuff over straw. One of the problems I had encountered when using the hornbeam wood, was that when I initially added the wood to the fire, the flames would jump up and burn the malt. I knew that using straw as a fuel source would be even more of a problem, since straw burns extremely hot and the flame tends to "explode" out of the fire and catch other things alight. (Hence why hay barn fires are so dangerous). From my earlier research, I came across a book on malt kilns and the author mentioned that the minimum height of the malting floor needed to be at least 16 feet from the heat source. This was going to cause problems in the small scale, but I figured that if I could suspend my wire-screen above the fire, I would at least give the malt some separation from the flames. I constructed a small malt kiln out of bricks and cinder blocks and used steel sheeting for the sides. I had about 4 feet of separation from the fire source.

After the malt kiln was constructed, I made a small wood fire in the base of the kiln and let it burn down to coals. I wanted to make sure I had a good heat source to keep the straw burning. Once that was done, I added small handfuls of straw to the kiln to see how it was going to burn. I quickly found out that using straw was going to be a major pain in the ass. The straw caught alight so quickly and burned so intensely that it either created a pillar of searing hot flame 7 feet high or produced billowing clouds of smoke. I tried compressing the straw and using it like that. This worked at first, as the fire burned the sides and top of the straw and produced a clean and hot flame. However, after a while the flames could not burn the compressed center and it began smoking horribly. In frustration, I threw an armful of hay onto the fire and the flames immediately burst out of the kiln, singing the hair on my arms and partially melting the shorts I was wearing! So much for that. Also, worryingly, I had created a 50 foot high plume of white smoke that was slowly moving across the neighborhood. I was expecting the fire department at any moment.

Finished 'diastatic' brown malt
After getting the fire under control, I figured out how to get the straw to stay alight without setting me and everything thing else on fire. I dismantled the front of the kiln and jerry-rigged the steel sheeting back together. I found that if I threw a small handful of hay onto the fire almost continuously, I could maintain a good, medium heat and not scorch the grain. So that is what I did. In five pound intervals, I lightly toasted/roasted the grain over the straw fire. The straw produced a very clean heat and the temperature on the wire screen hovered around 130F. After about a half hour of slowly drying the malt, I increased the fire and started to gently roast it. I didn't want the malt to burn or roast it too dark. After another 15 minutes, I had achieved a nice even toasty color with some charred bits of grain dispersed throughout the malt. I removed the malt from the kiln and added another 5 pounds of grain, repeating the process.

A word about the malt. Historically, they added green/wet malt to the kilns, essentially drying the grain before raising the temperature to roast it. It would take upwards of 12 hours to make a batch of diastatic brown malt. Obviously, I couldn't use green malt, nor tend the kiln for such a long time, so I used the palest and cheapest US-2row malt I could find (Rahr) and partially moistened the grain before adding it to the kiln. The whole time I was worried I was going to destroy the enzyme potential of the malt, but luckily I was able to darken the outside of the grain while still preserving a white, starchy interior. Also, I was really amazed at how little the grain smelled or tasted of smoke from from using the straw. I certainly reeked of smoke, but the grain did not.

After making the straw-brown malt, I figured I'd make another batch of the darker, highly roasted 19th century stuff. I split a bunch of hornbeam wood into small pieces and got a small fire going. Compared to using straw, making brown malt with hornbeam was a breeze, as it burns slowly and without much smoke. After another hour of lazily roasting the malt, I had some very dark - more burnt actually - 'porter malt.' I was done and just in the nick of time. It started to pour.

In review, half the battle of making the straw-kilned brown malt was getting the fire under control. I can see why using straw was both expensive and dangerous, as it burns extremely fast and the heat it produces at full burn is incredibly hot. I was careful to ensure that I didn't scorch the malt, although I would be amazed if the maltsters back in the 1700's were able to do the same. If they were indeed adding large amounts of straw to the kiln, they must have had some type of attemperator to regulate the amount of heat produced from the burning straw. Or maybe they were not burning the straw completely and the malt still didn't take on the smokey flavor due to the nature of the straw smoke? This is the problem with 18th century source materials, they don't talk about the details!

The real test will be to see exactly how "diastatic" my brown malt really is. Later this week I'll test a pound of it and go from there. With this malt, I intend to brew a mid 18th century porter so I can compare it to the ones I made previously. Imagine being able to sit down and try a 18th century porter next to a vatted and mild 19th century ones! 

Part I is here.


  1. Really good write up, and very interesting! looking forward to seeing what the porter looks like when you're done.



  2. Awesome stuff. Any chance you have the link to the Google book you mention?


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