In my three attempts, I have encountered stuck-mash city. Two batches had to be thrown out -- I couldn't even gather 1/2 gal of clear wort. I tried raking, pouring the mash back in the pot, and heating up to 165-170 °F (74-77 °C) and then trying again. I tried crushing with less flour also. I noticed that with decoction my first runnings were considerably cloudier than usual. I can only guess that decoction is not very easy with home brewing methods and equipment. Yet the sweet wort (what little I got) was the tastiest I've ever made; I found myself drinking a full glass of the stuff before I even realized what I was doing.

Are stuck mashes/sparges a common problem with homebrew decoctions? Am I wasting my time, effort, and money even bothering with it? I brew almost weekly and have had only one other stuck sparge, which happened when I used a good deal of rye malt, so I don't think it's my equipment or methods.

DM: There's no question it's easier to stick a decoction mash, because all the air and carbon dioxide bubbles (which tend to help float the grain husks in an infusion mash) have been boiled off. Also, decoction mashes are a lot thinner -- a typical decoction mash would include about 2 lb grist/gal water, as opposed to 3 lb grist/gal water for an infusion mash. Both of these factors make it all too easy to pack the bed down too tight during recirculation and runoff. A lot of fine material tends to settle right at the bottom of the lauter tun. While your slots must be narrow enough to hold back husk pieces, they cannot be so thin that they can be clogged by very fine particles.

Be sure to let your mash settle well in the lauter tun before you start recirculating. Give it at least 15 min without agitation. Also, be patient -- run the wort out slowly and pour it back on top very gently. The whole procedure is bound to take longer than with an infusion mash. Once you get into the sparge, you can cut the grain bed to assist the runoff. Just be sure to leave the bottom few inches undisturbed (for a full discussion of lautering and how to avoid stuck sparges, see BrewingTechniques' "Stepping Up" column in the May/June 1995 issue [2]).

Your description of your wort and your runoff makes it sound like you may be having more than the usual difficulties. Are you sure that you are using enough water for the mash (2 qt water/lb grist)? If not, the mash may end up like a bowl of oatmeal. When you heat the decoctions, do you put them through a starch conversion rest on the way up to the boil? Are you boiling the decoctions long enough (20 min)? Are you getting conversion in the mash tun? Unconverted starch can cause the mash to set up like cold oatmeal. Be sure when you take a decoction that you leave plenty of liquid in the main mash and cook mostly the grain fraction.

My experience with decoction mashing is not extensive. I consulted a very experienced home brewer who has done lots of decoction mashes, and he has on occasion encountered the same sort of difficulties you have. His advice is along the lines given above.

With care and patience, you can make decoction work. The recirculation-runoff-sparge cycle is touchy, but don't give up. A few American microbreweries make at least some of their beers by decoction, and many German breweries also use it, as do a small but growing number of intrepid home brewers. It can be done. Good luck.

Concerning sulfates, Mosher says that their use "enhances clean hop flavor and decreases hop bitterness" (p. 164). Your book, however, says that sulfates impart a "sharp, dry edge to hop bitterness" (p. 42).

Could you elaborate on the apparent contradiction?

DM: It's hard to argue with Randy Mosher, who is truly a world-class brewer. Maybe the differences between our perceptions has to be chalked up to individual differences between his taste buds and mine. In all candor, however, I have to say that I have not found that sulfate decreases hop bitterness -- quite the opposite, it gives it an edge.

One possible way to accommodate our differing views might be to point out that the character of sulfate depends very much on the other water ions present with it. High levels of sodium and/or magnesium (ever tasted Epsom salts?) exaggerate the effects of sulfate, making the beer harsher. As it happens, all my brewing before I moved to Nashville was done with river water that had fairly high levels of both of those ions. That may explain my aversion to sulfate and my preference for calcium chloride as a salt for mash pH adjustment.

I would venture two further comments, and I think Mosher would agree with me on these. First, if you are brewing beer from malt extract, you have no need to get into "water adjustment." The water was already adjusted when the extract was made. You have no need to add mineral salts to your reconstituted extract wort to get the pH right. Second, if you are brewing pale beers from grain, add only enough calcium salt (sulfate or chloride) to the mash water to bring the calcium content to 50-100 ppm. Use acid if necessary to pull down the pH of your sparge water. As a general rule, only change your water if you have some compelling reason to do so.

DM: Sorry, but I can't. Lead is not required for yeast metabolism. If there is lead in the wort, the yeast may take some of it in, but to the extent that this happens the health of the yeast will suffer. In fact, the harm to the yeast is a second and almost equally compelling reason for avoiding lead solder when assembling brewery piping and equipment. On the other hand, it is true that very low levels of lead exposure are unavoidable and don't seem to do much harm to most people. But the stuff is basically bad for you, and there's every reason to stay away from it.

Why are you worried about lead in the wort? If you have brass fittings in your brewery equipment, why not give them the peroxide-vinegar treatment prescribed in the article to which you refer? Then you can stop worrying and enjoy your homebrew.

To contain the wort, I would like to use a food-grade 5-gal bucket (the type that is often used as a primary). The surface of the wort and the lid will be separated by an air-space of about 3 in. The wort will be prepared using a full-grain step-infusion mash. I have had success in the past refrigerating 10 gal of wort in a grief, but it was only for 24 h, and the mash was made from concentrate.

Do you think the airspace in the bucket could be a problem for contamination? Should I flush the air out with carbon dioxide? Would I have to re-aerate the wort before fermentation, or could I just pitch the yeast when it reaches room temperature? Would it be better to freeze it or would that deteriorate the wort? What types of deterioration would the wort likely undergo if it were refrigerated for an extended period (effect on hop aroma, for example)?

DM: Yes, the headspace in the bucket, as well as the bucket itself, could be a source of contamination. Flushing with carbon dioxide should help.

Personally, I would be afraid to freeze the wort for fear of precipitating too much cold trub, which the yeast needs during the lag period for growth. It might not matter, but the only way to find out would be to try it.

Hop aroma might be affected somewhat during storage because it tends to diminish with time under normal circumstances.

Far and away the most likely deterioration, however, would be infection by "wort spoiler" or other bacteria. No matter how much effort you put into cleaning and sanitation, wort -- unless it has been canned or autoclaved in the container, which is impossible with a plastic bucket -- is never going to be 100% sterile. It is a perfect growth medium for many types of microorganisms.

The best advice I can offer is first, reconsider your proposed action. If you have some truly compelling reason not to aerate and pitch the wort immediately after cooling, then store it for as short a time as possible. Second, cross your fingers, knock on wood, light a candle, do anything you can think of to enlist supernatural aid. You're going to need it.

I sometimes get interrupted during my all-grain mash sessions and have to put my brewing on hold. Recently I interrupted a boil for 4 h (1 h of boil, 4 h rest, and 15 min reboil). On another batch, I had to leave my mash out for 2 h extra. What happens to the beer when allowed these unwanted rests? Are there crucial times that should not be extended, or those where an unplanned rest would be of no consequence? Are there remedial actions that can be taken?

In another batch of beer (6 gal of stout), I used 2 lb of barley that I had pressure-cooked before mashing. The sparge stuck (my first ever), and the fermentation was over in two days going from specific gravity of 1.050 to 1.020 in spite of a quart of fresh yeast (1 pint settled out, 1 pint liquid). The sweetness of the fermented stout was evident. Is this the Crabtree effect? What happens to sugars when you pressure-cook barley or other grains?

I don't have a recirculation system, and I frequently mash in at 132 °F (56 °C) with 3/4 qt/lb, then gradually add 1/2 qt/lb boiling water plus steam to raise the temperature to 155 °F (68 °C). During the 11/2 h rest, it cools to 145 °F (63 °C) as the saccharification rest is completed. Does the same sugar conversion take place during cool-down as during heat-up?

Finally, the beers were hazy. The hops in the beer with the 4 h rest were less than expected.

DM: Unwanted rests. Extending the mash saccharification rest would tend to produce a thinner beer because of an increased breakdown of dextrins into fermentable sugars. The other effect would be some souring of the mash, owing to the action of the thermophilic lactic bacteria that are naturally present in malt.

Whether you could detect either of these effects would depend on the temperature and length of time the mash had to wait. To minimize both, I would try to heat the mash to 168 °F (76 °C) before proceeding with recirculation (assuming you don't already do this). That will stop the enzymes. Also, the extra heat might slow down the Lactobacillus bacteria, though it won't kill them. When you sparge, collect the wort in your kettle and start heating the kettle as soon as the bottom is covered. That will kill off the Lactobacillus as soon as possible -- they can't survive much over 180 °F (82 °C).

I'm not sure why your interrupted boil gave less hop utilization than normal. I don't know of any experiments along these lines in the literature. It may be that the abnormal heating and cooling cycle resulted in more precipitation of hop resins with the trub in the kettle. You now know that, if it happens again, you will have to add more hops when you restart the boil. The haze may be related to precipitated matter redissolving when the cooled wort was brought back to a boil.

These effects seem like good reasons to avoid interrupting and resuming the boil. You might be better off just cutting it a little short, if need be.

Pressure-cooking barley. Pressure-cooking barley is a dangerous way to make a stout. The stuff will gum up your mash, as you found out. It may also gum up the relief valve and the outlet nozzle (the little nipple that the rocking weight rests on) of the pressure cooker itself. If that happens, your kitchen utensil could become a fragmentation grenade.

The set mash, and the haziness and high gravity of the finished beer, point to an incomplete conversion of the carbohydrates from the barley in the mash tun. The gummy starch material plugged the mash filter bed and also got washed into your kettle and eventually ended up in the finished beer. The fermentation was not the problem -- though you did overpitch. Next time, try using brewer's flaked barley and I bet you will have no trouble.

Enzyme activities and temperature. The enzyme activity during the cool-down of your mash is not the same as during heat-up. In fact, my guess is that you could cut your saccharification rest to 1 h or less without having any effect on the fermentability of your wort. This is because b-amylase (which makes maltose) can survive for only a limited time at high temperatures, and the higher you heat the mash at the beginning of the saccharification rest, the shorter its survival will be. It is impossible to predict exactly, because enzyme survival depends on the thickness of the mash and other factors as well as temperature. If you want a highly fermentable wort, however, you must keep the mash temperature on the low end of the saccharification range so that the b-amylase has time to do its work.

References

(2) Jim Busch, "Lautering for Highest Extract Efficiency," BrewingTechniques 3 (3), 22-25 (1995).

(3) Dave Miller, Continental Pilsener (Brewers Publications, Boulder, Colorado, 1990).

(4) Randy Mosher, The Brewer's Companion (Alephenalia Publications, Seattle, 1994).