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Calculating Hop Bitterness

Calculating Hop Bitterness

By David Cordrey
(This post was restored from the old site, and contains some really good and knowledgeable information, and deserves to be kept up. If you are reading this David and would like it removed just contact us) Props to David for the awesome write-up.

How hop bitterness is determined:

The bittering agents in hops are found in the soft resins of the hop flower. These chemical agents; Humulone, Cohumulone and Adhumulone collectively are refered to as Alpha Acids. Alpha acids themselves are not soluable in water or beer wort, however, at elevated temperatures (~212°F) Alpha Acids go through a chemical change called isomerzation. These Iso-Alpha Acids are partially soluable in water and beer wort.

When you buy hops the Alpha Acid content is usually stated in percent by weight. Typical values are 4 to 12%, depending on the hop variety. The amount of iso-alpha acids that are actually dissolved in the wort are typically only 15 to 20% of the total alpha acids available in the hops, depending on the boil time and specific gravity of the wort.

The bitterness of beer is commonly measured in International Bittering Units (IBUs) representing the the amount in parts per million of dissolved iso-alpha acids. Both the AHA and BJCP publish guidelines for hop bitterness in IBUs for the various beer styles. Since the equipment and methods to actually measure iso-alpha acid concentration is beyond the reach of homebrewers, a method to estimate IBUs must be employed by homebrewers. Fortunately, this is a straight forward calculation which can be applied when formulating a recipe in which a target IBU range is sought.

W * A * U * .7489
B = ————————–
V * (1+(G-1.050)/0.2)

B = bitterness in IBUs
W = weight of hops used in ounces
A = the weight percentage of alpha acids in the hops
U = the percent utilization of alpha acids
V = the volume of wort
G = the specific gravity of the wort

The alpha acid utilization is based primarily on boil time, but is also affected by specific gravity of the wort and whether the hops is in pelletized or whole form. Typical Utilazation factors are in the range of 15 to 25%. Pelletized hops have about 20% more bittering potential than whole hops because the soft resins have been upset and made more available during the pelletizing process. Thus, it can be seen that the the bittering potential of hops in beer is a function of the amount of hops used, the amount of alpha acids in the hops, length of the boil time, the volume of wort and the specific gravity of the wort.

Estimating the Utilization factor:

In his book Designing Great Beers (Brewers Publications, 1996), Ray Daniels presents tabulated data on hop utilization which I have used to come up with the following formulas based on boil time and whether or not pelletized hops is used:

For Whole Hops use:

U = -(.0041 * Time^2) + (0.6261 * Time) + 1.5779

For Pelletized Hops use:

U = -(.0051 * Time^2) + (0.7835 * Time) + 1.9348

Where Time is in minutes.

The above formulas assume a 1.050 specific gravity wort. Correction for other specific gravities is made in the denominator of the first formula.

These formulas can be easily input into a programmable calculator or spread sheet for ease of use. Otherwise this graph can be used to estimate hop utilization.

In Summary

It is important to remember that these formulas are only estimates for predicting the IBUs in a given beer. Only laboratory analysis can tell you exactly how many IBUs are in a given beer. These formulas are useful tools for predicting the bitterness of a recipe or for determining how much hops of a given Alpha Acid content to use to hit a target bitterness level.

Decoction Mashing, Part 1

Decoction Mashing, Part 1

Demystification of the Decoction Mash

(This post was restored from the old site, and contains some really good and knowledgeable information, and deserves to be kept up. If you are reading this David and would like it removed just contact us) Props to David for the awesome write-up.
By David Cordrey

Of the three mashing methods Single Infusion, Step Infusion and Decoction, decoction mashing remains a mystery to many homebrewers. Single infusion mashing is by far the most common mashing technique and is employed by most all-grain homebrewers. Some homebrewers use a step infusion or temperature controlled mash which includes a protein rest, but few and far between are homebrewers that have ever tried to conduct a decoction mash.

In this article, I’ll attempt to demystify the decoction mash by explaining what decoction mashing is, what it’s benefits are and what beer styles have traditionally used decoction mashing. In Part 2, I’ll talk about how to successfully conduct a decoction mash in the homebrewery.

Webster’s defines:

  • “Decoct” 1) to extract the flavor of by boiling 2) boil down, concentrate
  • “Decoction” 1) the act or process of decocting 2) the extract obtained by decocting

From these definitions it stands to reason that a decoction mash involves the boiling of the water/malt mixture, and that the intent is to extract and/or concentrate flavors.

But how can that be? The first thing an all grain brewer learns is that if a mash is boiled, the precious amylase enzymes will be destroyed preventing starch conversion, and excessive amounts of tannins will be leached from the grain husks, leaving an undesirable astringent flavor. The answer to this paradox, as you’ll soon see, is that careful technique overcomes these potential problems; indeed, a decoction mash when performed properly results in a beer with the highest malt flavor profile and highest extract yield of the three mashing techniques. Decoction mashing also results in less hot and cold break material, and reduces the mash pH naturally, without the addition of dark malts, lactic acid or other water treatments.

In decoction mashing, a portion of the mash is removed from the mash tun and is transferred to a boiling pot. This portion is called the decoction, and it is heated slowly to bring it to a boil. After boiling for a period of time the decoction is added back to the main mash, thereby raising it’s temperature. In this respect, the decoction mash is similar to the step mash or temperature controlled mash. For example, the initial mash temperature and volume of the decoction can be chosen so that the temperature rise goes from the protein rest temperature to the sacharification rest (starch conversion) temperature. This would be called a single decoction mash because only one decoction was made. An additional decoction can be made to raise the mash temperature again to mash out (double decoction) or a total three decoctions (triple decoction) could be used to achieve an acid rest – protein rest – sacharification rest – mash out profile.

Long ago brewers had worked out the details of decoction mashing for beer making – even before the thermometer had been adopted by brewers. Proper strike water temperature was by achieved mixing measured volumes of boiling and ambient temperature water, and mash rest temperatures were achieved by mixing boiling and non boiling mash fractions. Through trial and error, good luck and patience these early brewers discovered the proportions of each needed to effectively step through the various temperatures to acidify the mash, degrade proteins, and convert the malts starch into the fermentable malt sugars.

In fact, a simple infusion mash using the under modified malts of this period would have produced weak, hazy, inferior beer. Decoction mashing was an enabling technology for clear pale beers like those produced in Pilzn. You see, by boiling the grain, starches dissolve and insoluble proteins are denatured and coagulate as a scum on the top. The vital amylase enzymes are quite soluble, so if a “thick” decoction mash is pulled for boiling, the “thin” rest mash contains almost all of the enzymes where they are safe from heat degradation. When the decoction is added back, the dissolved starches are immediately available for the enzymes in the rest mash to go to work on, and the rest mash temperature is raised. The proteins that coagulate in the decoction are usually skimmed off the top before the decoction is added back to the rest mash, which improves wort clarity.

Eventually, maltsters in Britain learned how to make higher modified malt, the thermometer was accepted as a brewing tool and infusion mashing was born. This technique enabled shorter brewing sessions, the use of less fuel and in general lowered the cost of beer; all good things considering beer sustained many a laborer during Britain’s industrial revolution.

Decoction mashing did not die. In fact, to this day most European lagers still use a decoction mash, even though their malts are now have a high degree of modification. And not just because they are steeped in tradition. Infusion mashing is not prohibited by the Reinheitsgebot. But, decoction mashing produces a richer malt profile with complex caramelized flavors that are the hallmarks of most continental European beer styles, particularly Pilsner, Marzen, Bock, and especially Dopplebock.

The specific flavoring agents produced by decoction mashing have not been rigorously identified by chemical name, but it is presumed that they are the result of certain browning (melanoidin) reactions and caramelization. These are the same types of reactions that happen when you cook a roast in the oven. An analogy can be drawn between oven roasting vs. microwaving a roast and decoction vs. infusion mashing malt. The browning reactions require the presence of protein and sugars and carmelization requires a high sugar concentration. While carmelization does occur in the main boil, the concentration of sugars is generally higher in the mash so decoction mashing will give more carmelization than wort boiling. The browning reactions are not as prevelant in the boil because the wort has been separated from the grist, and there is not a sufficient amount of protein in clear wort to support them as much. These browning reactions, and high sugar content in the decoction also serve to lower the pH of the decoction so that leaching of tannins form the grains husk is not a problem.

There has been a trend in continental Europe recently of brewers moving away from the triple and double decoctions as a matter of economics. Many are now using a single decoction, though rumors have it that a few are either using or experimenting with infusion mashes. Today’s highly modified malts, the availability of large variety of specialty malts, superior milling, automated temperature control and superior water chemistry have all lessened the requirement for triple decoction mashes. However, even a single decoction will produce malt flavors unobtainable by any other means.

Hopefully the craft of decoction mashing won’t be entirely lost among commercial brewers for economic reasons. As homebrewers we should be prepared to carry the torch and keep this historic and beneficial technique alive. In Part 2, I’ll explain how to get started decoction mashing at home with a minimum investment.

Decoction Mashing, Part 2

Decoction Mashing, Part 2

Decoction Mashing at Home

(This post was restored from the old site, and contains some really good and knowledgeable information, and deserves to be kept up. If you are reading this David and would like it removed just contact us) Props to David for the awesome write-up.
By David Cordrey

In Part 1 of this subject I described what decoction mashing is, extolled it’s benefits, and gave a brief history of its origin and what styles showcase decoction mashing’s added character. In Part 2 I’ll describe the practical aspects of decoction mashing. This is a “How To” primer on the subject.

You may ask yourself “Why on earth would I want to do a decoction mash at home?” – I make damn good beer using infusion mashes. I use highly modified quality 2-row malt, I don’t need to decoct. I don’t want to hassle with a bunch of extra process steps to make my beer. I’m afraid I’d screw up a batch by boiling grains.

These are all valid points. But what if you wanted to make a killer Dopplebock? Adding Crystal and Munich malt to an infusion mash will help add sweetness, but just won’t give the same perceived maltiness as a decoction mash. What if you wanted to replicate the procedure to make a Bohemian Pilsner? Authenticity would dictate a decoction mash. What if you were making a Pale Ale or Bitter or any other style using an infusion mash and you missed your mash temperature? A small decoction could get you back on track without thinning out the mash excessively by just adding more hot water.

Decoction mashing is a technique that homebrewers should have in they’re repertoire. And believe me, it is easy to master. Once you get used to the technique, you’ll probably use it a lot!

What You’ll Need:

To get started you’ll need the following extra equipment:

  • A second stainless or enamel finished boiling pot at least one third the volume of your mash tun.
  • A large long handled slotted spoon or strainer.
  • A small approx. 1 to 2 quart size container (Tupperware works fine).
  • A heat source for boiling the decoction.

Chances are you have everything you need at home already. I use the small 3 gallon pot I started brewing in, a big plastic slotted spoon from the kitchen, a thoroughly cleaned quart size yogurt container and my Cajun Cooker.

How to Decoct

The big question in decoction mashing is how much mash do you pull out for boiling? If you don’t take enough mash the temperature rise will not be as great as desired; too much will result in overshooting your desired temperature. Fortunately there is a good “rule of thumb” to follow for decoction mashing:

Dough in using 1.33 qts. of water per pound of grain and stabilize at 122°F.
Use a thick portion of the mash consisting of 40% the quantity of grain in the decoction.
Temperature gain will be approximately 28°F per decoction.
This rule of thumb is easy to remember, and fits the temperature profile for a single decoction nicely. If you want a different temperature gain, you can calculate the decoction fraction as follows:

F = ( Tf – To ) / ( 212 – Tf- K )

Where: F is the fraction of the main mash to boil. (multiply by 100 to get %), To is the starting temperature in °F, Tf is the desired final temperature in °F, K is your temperature loss constant (17°F for my system). The value for K can be adjusted ± a few degrees to fit your own results.

When plotted in graphic format, the results look like this:

As can be seen, this formula predicts that as the starting temperature increases, a larger decoction needs to be pulled to result in the same temperature gain.

I always try use 1.33 quarts of water per pound of grain for both single infusion and decoction mashes – just as a matter of convention, not because this is a magic ratio. Different ratios can be used, but will affect the temperature gain because water and grain have different specific heats. For water/grain ratios of 1.25 to 1.5 qts/lb the above rule is close, however, and can be accommodated by changing the “K” term.

Detailed Procedure

Definition of a “thick mash” is a little tricky. It is important to allow the gain to become fully hydrated (absorb all of the water it can) before pulling the decoction. Stir the mash well and let it soak for 5 to 10 minutes at the initial rest temperature. Then using your large slotted spoon, scoop out the wet grain into your quart size cup and transfer to the small (cold) boiling vessel. The grain should pile up in a ball in the pot. Scoop out a third of the grain. I’ve found my 1 qt. container holds very close to a pound of dry grain. If I’m mashing 15 lbs. total, one third of that would be 5 scoops for the decoction. Now pull out some liquid from the main mash in your container and slowly add it to the pot until the pile of grain begins to slump. Stir it up, it should resemble the consistency of thick oatmeal, with some liquid between clumps of grain. Don’t forget to cover up and insulate the main mash. You don’t want it to cool off while you’re boiling the decoction!

Start the fire under the decoction mash and heat it up slowly, stirring constantly to prevent scorching. As it nears boiling, it will appear to thin out some and a scum layer will form on top. Keep it on a low boil for as long as you want to conduct the initial main mash rest, scraping the scum off occasionally, and stirring frequently. I generally boil for 20 to 30 minutes. Be careful not to scorch or burn the grain, add a little more liquid from the main mash if this looks like it might happen. The longer the boil, the more the flavor impact it will have; I’ve gone as long as 45 minutes with the decoction boil. A short boil will net the same temperature rise, but with less flavor impact.

Now carefully dump or scoop the decoction mash back into your mash tun. Try not to splash too much or spill it down the front of your shirt. If you wear glasses and can see Okay without them, take them off first. I’ve had a few near accidents when my glasses steamed up so bad I couldn’t see at all. Once you have successfully transferred the decoction back to the mash tun, stir it all up thoroughly and cover to let the temperature stabilize. You should wait at least 5 minutes before checking the temperature. Everything should be Okay now, just continue this rest for the desired time. That’s it for a single decoction mash. Just sparge and collect the wort like normal.

Multiple Decoctions–The Ultimate Experience

For multiple decoctions, just repeat the procedure to step through your temperature ranges. The 28°F rise described in the previous section fits nicely with the temperature step profile that is desired for a single decoction mash. If you dough in to achieve a 122°F first rest (protein rest), a single decoction will get you to the conversion rest temperature of ~150°F. A second decoction would heat the mash to above 170°F for a mash out. A triple decoction profile could be employed to rest at four different temperatures. The more decoctions you use will increase the number of melanoidin reactions and carmelization, and thus add more of the “malt character” that is associated with decoction mashing.

The possibilities are virtually unlimited as far as temperature profiles you can create. Traditionally the rest temperatures that are used with decoction mashing are as follows:

  • 95-110 °F Acid / Gluconase Rest
  • 120-127 °F Protein Rest
  • 145-159 °F Sacharification (conversion rest)
  • 170-178 °F Mash out

Which rest temperatures you want to hit, will determine the number of decoctions you will use. The most common decoction mashing profiles are:

Single Decoction: Mash in at the protein rest temperature. Use a single decoction to reach conversion temperature.

Double Decoction Mash: Mash in at the protein rest temperature. Use one decoction to reach conversion temperature, then a second decoction to mash out. Typically used for sweeter beers with a higher conversion temperature. The “mash out” destroys any residual enzymes that might further break down any dextrins during sparging.

Triple Decoction Mash: Mash in for an acid or glucanase rest, then perform three separate decoctions to hit each of the temperature ranges. An acid rest helps lower pH and thus starch conversion when using all pale malts and very soft water, such as might be the case when replicating a Bohemian Pilsner.

These rest temperatures were developed over a long time by trial and error to fit the circumstances faced by brewers hundreds of years ago. The merits of each rest and impact of what temperature to hit in each range are often debated and hence are subjects for another article. There are plenty of books covering this subject in detail. Papazian’s The New Complete Joy of Homebrewing is a good primer on this subject.

Go For It!

You now have all of the information you need to try decoction mashing on your very own. Go for it! Take the plunge. Really, your chance for failure is very, very small. Your chance for outstanding success is great. The temperature ranges are broad enough you’re going to end up somewhere in the ballpark. My experience is that I have never overshot by more than 2°F. When I err on the low side by 5°F or more I just do an extra, small quick decoction to get back on track.

Remember, proportionally smaller or larger decoction volumes will net lower or higher temperature rises. Short boil times will give the same temperature rise without affecting flavor or color very much. These facts are useful for making small temperature adjustments. So if you miss your target temperature in an infusion mash, use the formula or graph above and just pull a small decoction to boost it up a bit.

For certain styles, decoction mashing is the only way to get the “malt character” that is required. Decoction mashing also can give a pleasing complexity in styles that don’t traditionally use decoction mashes. Scotch Ales, for instance, can be easily given a malty finish through the use of a decoction mash.

Decoction mashing is a technique that is well worth mastering. You may not use it for every batch, but it should be in your repertoire for making traditional lagers & bocks, correcting mash temperatures, or adding malt character to any beer.

Wort Chiller Basics

Wort Chiller Basics

(This post was restored from the old site, and contains some really good and knowledgeable information, and deserves to be kept up. If you are reading this David and would like it removed just contact us) Props to David for the awesome write-up.

By David Cordrey

Okay, so you’ve got a few batches of homebrew under your belt, and you’ve got the hang of the basics. Your beer is pretty good, but maybe lacking some of the finer points; slightly oxidized, maybe some sulfury flavors or other funky off-flavors. So your thinking about moving up to all-grain brewing or at least to full wort boiling (the next logical step in the evolution of a homebrewer), and your friends at the club meeting or down at the homebrew supply shop tell you ought to get a wort chiller. “What the heck is that”, you ask? And your friends’ reply, “it’s a thing you use to quickly chill your hot wort to yeast pitching temperature. It helps prevent wort oxidation, lowers dimethyl sulphoxide levels and greatly reduces the time your wort spends in the 120-80 °F temperature range that incubates sorts of nasty bacteria. YOU REALLY GOTTA GET ONE!”

Try barrel-aged beer with these small oak barrels from Top Shelf Barrels

But there are so many to choose from. What’s best immersion or counter flow? Are the store bought ones better than homemade? As you query other homebrewers you find that there isn’t a hard and fast rule. Everyone seems to have a different opinion, have different setups and all claim success. However, everyone says YOU GOTTA GET ONE! What should you do?

Hopefully this article will answer most of your questions, so you can intelligently make a decision on how to approach this dilemma. But first let me reiterate, if you want to improve your beer making, you GOTTA GET A WORT CHILLER! No ifs, ands or buts about it. Quickly chilling wort before yeast pitching will make better beer. The style of wort chiller and whether you make it or buy it are all personal choices you will make for yourself after you read this article and assess your needs and abilities.


Immersion or Counter-Flow?

The first big question, and truthfully, they both work fine. The names are pretty self explanatory. After a brief description, the pros and cons of each will be examined.

An immersion chiller is immersed into hot wort while cold water at one end and circulates around inside of it. Heat is exchanged from the hot wort to the cold water. As the water circulates it heats up and is expelled out the other end of the tube. The entire volume of wort is chilled down in the boiling kettle, to be drained or siphoned off into the primary fermenter when cool enough to pitch the yeast. It is a simple device.

In a counter-flow chiller, hot wort is passed through the inside of tubing which is surrounded on the outside by cold water that is flowing in the opposite direction. In this method, the wort is chilled from near boiling to room temperature very quickly, a little bit at a time. A couple of styles are common: 1) A copper coil is threaded inside a garden hose and fittings attached so that water flows though the hose around the outside of the copper. 2) A copper coil is placed inside a cylinder that has water flowing through it. The typical arrangement is to have the chiller situated directly between the kettle and fermenter, so as the cold wort is deposited directly into the fermenter. A bit more complex than the immersion chiller, but definitely not rocket science.

Style 1 Style 2


Pros and Cons of Immersion Chillers



  • Simplicity. Often overlooked, but simplicity may be better for you.
  • Ease of sanitization. Blow the water out of the inside and hose it off good when your done. Next time you use it, hose off the dust and throw it in the kettle 15 minutes before the end of the boil… it’s self sanitizing!
  • Simplicity. Can’t say enough about that!
  • Cheaper than counter flow
  • Since the entire batch is cooled at once, the time spent in the dangerous temperature zone is greater than with a counter-flow chiller. Especially for large batches.
  • Typically doesn’t chill the wort as low in temperature as the counter-flow variety.
  • If your kettle is on the small side, it may overflow when you dunk your immersion chiller into it. (A “pro” if this is the only excuse you need to get a new kettle too!)
  • Prevents the use of a hop-back for infusing hop flavor & aroma into the wort.
  • If you don’t hose it off right away after use it becomes a sticky magnet for animal hair, dust and old newspapers.

Pros and Cons of Counter-Flow Chillers



  • Wort is chilled rapidly from near boiling to <70°F, minimizing the amount of time spent in the temperature zone where it is most susceptible to infection.
  • Wort can be chilled to nearly the same temperature as your cold water supply.
  • A hop-back can be easily added between the kettle and chiller to get intense hop character in your beer.
  • Not limited by kettle volume.
  • Faster than immersion.
  • More parts and hoses to hook up than an immersion chiller.
  • Brewing setup is a little more involved. Need to have kettle high enough to maintain siphon through chiller to fermenter.
  • Requires thorough cleaning / santizing before and after each use.
  • More complex than immersion.
  • More expensive than immersion.

So what’s right for you? That depends on how much time, money and effort you want to invest. Both types of chillers get the job done, and offer certain advantages over the other. If your just getting started, doing small boils (5 gallons or less), or don’t have your brewing routine worked out I’d recommend an immersion chiller. If your interested in adding a hop back, doing large batches or are concerned with long lag times between hot and cold wort you should consider the counter-flow variety.

I actually have both and use one sometimes and the other one other times. I started with a store bought cylinder type counter flow chiller. After moving into a new house I made an immersion chiller, because of its simplicity, which made it easy to use in a new locale. Recently, I made a coil-in-hose counterflow, after the PVC pipe outer cylinder on my old CF chiller split open with the high pressure water we have at my house. I find myself preferring the counterflow chiller, now that I’ve got my new brewery fully functional, because it gives me faster and colder cooldowns. I boil a little extra sparge water and run this through the chiller (with no water counterflow) before use. Then I run about 16 oz of boiling wort through the unit and let it sit in the chiller scalding hot before turning on the water. This sterilizes the inside of the tubing. I use the small sample for measuring the OG and as a first taste. After use I run some more of my left over hot sparge water through the unit, followed by a weak iodophor solution. I cap the ends of the tubing then store it for the next time.

Make of Buy?

More decisions. You can buy either variety of chiller off the shelf at just about any homebrew supplier. Most of the units I’ve seen are of good quality and should work well. And, if they break or don’t work you can blame it on someone else! On the other hand, you can also buy all of the parts to build either type for alot less money. If you’re on a budget, or just like to tinker around building things you’ll want to build your own!

When building your own, remember size matters! Don’t scrimp on the copper tubing, more is better!Use 50 feet of 3/8″ copper minimum for an immersion chiller. More like 100 feet if you’ll be doing 10 gallon batches. (Most store bought immersion chillers are way too small for more than 5 gallons). For counterflows, 30 feet of 5/16″ tubing inside a 30 foot garden hose seems to work pretty good, but 50 feet of 3/8 tubing inside a 50 foot hose is faster & better. For a cylinder style counterflow, you might consider using a spare 5 gallon bucket as the cylinder (make sure the water outlet is large enough or you’ll blow the lid off of it!) You should use soft copper “refrigerator” tubing. You can find the tubing and all of the fittings you need at Home Depot or any hardware store. Clean everything thoroughly before first use. Hot distilled vinegar followed by plenty fresh water works well for cleaning the copper, or you can use a commercial beer line cleaner.

So now you don’t have much of an excuse for not chilling your wort! It’s not hard to do, doesn’t have to be expensive and your beer will thank you! CHILL OUT & GO FOR IT!