First you start with grain. Nowadays when we don't qualify the terms "beer" or "ale" we usually (but not always) mean something made out of barley. That distinction wasn't made in the middle ages and they used barley, wheat, oats and rye without necessarily distinquishing that in the name of the beer. Unlike modern, cheap lagers, they did not use rice. The specific variety of a grain affects the flavor. I'm using the word "variety" in the botanical sense. Domestic barley is "hordeum vulgare." There are two cultivars of barley used for brewing: 2-row and 6-row barley. 6-row barley didn't exist in the middle ages. Varieties of 2-row barley are things like "Klages" or "Moravian III." We generally don't know what varieties of grains they used in the middle ages. Where and how the grain is grown affects its flavor too.

Next you malt the grain by getting it to sprout. This is generally done by spreading it on a floor and soaking it with water for a period of time. We don't have any technical documentation on medieval malting. Also, nowadays brewers don't usually do their own malting. There are companies that malt the grain and then extract the fermentables and ship that in the form of syrup to the brewery. The extraction process affects the flavor. Anybody who uses malt extract can't honestly claim to be using a medieval recipe.

Next you dry the malt. This can be done on the malting floor in the right conditions, but was normally done in a kiln of some kind. We don't have any technical documentation on how malts were kilned in the middle ages. This also affects the flavor.

Next you mill or "crack" the malt to produce "grist." This is normally a very course grind; just enough to open the kernals. Too fine a grind makes a mushy mash. (I'll explain mashing in a minute.) We don't have any technical documentation on milling malts in the middle ages.

Then you heat the grist in a kettle of water. This is mashing. Mashing causes all kinds of chemical stuff to go on which determines how much sugar of what kinds are extracted from the grain. Temperature and time are critical to this step. Needless to say, doing this in a copper kettle over a wood fire was an art. We have no technical documentation on mashing in the middle ages, and it would probably be impossible to create any since they couldn't measure temperature or time precisely.

The liquid drawn off from the mashing is called the "wort." Some medieval brewers didn't transfer the wort to a separate kettle, instead they scooped out as much of the grist as they could from the mashing kettle and then went onto the next step. Normally, however, the wort was tranfered to a new kettle for the next step.

Now the wort is boiled. This is normally when other flavorings, like hops and spices, are added. The boiling partially (but not completely) sterilizes the wort and releases the esters and liquors in the additives. Exactly when during the boiling the additives are put in affects their flavors. In modern beers it is common to put some of the hops in at the beginning and then some more near the end of the boil. We don't have any technical documentation on when the additives were put in during the boiling in medieval brewing.

The additives are their own story too. We know generally what they put in, but just like grains, we don't know varieties, and we don't know the growing conditions. There is archeological evidence of hop growing all over Europe from Roman times on, and there are import and export records of hop shipments, but that doesn't tell us what we need to know to actually flavor a beer correctly. Another problem is figuring out what "gruit" is. This was the most popular beer additive before hops became common and we have only a rough idea what it actually was.

After boiling, the wort is cooled and yeast is added. The yeast consumes some of the sugars in the wort and gives off alcohol and carbon dioxide. Different varieties of yeast have different flavors themselves, consume different sugars, and have different alcohol tolerance. The interaction of the kind of yeast and the kinds and amounts of sugar in the wort determine how much sugar, alcohol, and carbon dioxide is left in the finished beer.

Yeast was first identified by Louis Pasteur under a microscope in the 1850s. Medieval brewers had no idea what was actually causing the fermentation in their beer. They just knew that if you took some of the goop left over from a previous batch and added it to a new batch, it would start to ferment. None of this was done in a sterile environment, so all kinds of other stuff could get into the wort and start eating the sugars.

The wort needs to ferment for anything between a few days to a few weeks in an open vessel so the gas can escape. Yeast is temperature sensitive, so the ambient temperature in the fermentation room affects the outcome. We have no technical documentation on how they fermented their beers.

Finally, the beer is poured into casks. Depending on where the yeast is in its life cycle, fermentation can continue in the casks further affecting the sweetness or dryness of the beer and the amount of fizz.

That is a very abbreviated description of brewing, but I think it serves to illustrate how complex the process is and why it is virtually impossible to say whether or not a particular brew is an "authentic medieval beer." There is just too much we don't know. Even if you have a list of ingredients with specific quantities, you still have no idea how the beer will come out without knowing what the details of the brewing process should be.

Best Regards,

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1. Water -- Obviously the water you use affects the taste. Some places were noted for the distinctive taste of their water, like the hard, salty water from Burton-on-Trent and Newcastle.

2. Fining -- this is the process of clarifying the beer. You can do this by filtering the beer, just letting it sit quitely for a couple of months, or by adding isinglass. Isinglass is gelatine made from the swim bladders of fish. They used it in the middle ages to accelerate the precipitation of the yeast out of the beer. If you add isinglass to the beer, all the yeast will clump together and settle to the bottom.