The following problems can happen to both extract and all-grain brewers. The all-grain brewer may have an easier time dealing with some of them because of the increased control that mashing gives the brewer.

Poor head retention and thin body: Medium- and large-sized proteins are necessary for good body and foam retention in beer. A protein rest during the mash can reduce the concentration of these proteins to unacceptably low levels. All of the barley malts I have worked with are quite well-modified and require no protein rest (Briess Malting Company says that even its wheat malt does not require a protein rest).

Some brewers will try to compensate for a lack of body in their beers by using a high saccharification temperature to create a less fermentable wort. Be aware that this does not really increase body. It does make a sweeter beer but in the extreme it can taste "worty" and underattenuated.

Haze: Chill haze, as the name implies, forms only when the beer is cooled, and it's reversible early in the beer's life (the beer clears when warmed). Protein-tannin complexes that are soluble at room temperature precipitate at cool temperatures. These suspended particles scatter light, causing haze.

Chill haze can be minimized by good brewhouse practices: Ensuring a good hot break and cold break and minimizing the amount of high molecular weight protein degradation products in the wort. Even with the best brewhouse controls, beers will throw some chill haze. If you want your beer to be completely clear, you can use fining agents, filtration, or long, cold lagering (yes, even for ales).

If the beer suffers from haze regardless of temperature, it is called "permanent haze." This condition can be caused by the presence of starch in the beer, nonflocculent yeast, or bacterial contamination. To test for the presence of starch you can drop some iodine into a sample of the beer. The iodine will turn black-blue in the presence of starch.

The presence of starch in the beer indicates incomplete saccharification or too high a temperature during the lauter. If the temperature of the grain bed gets much over 170 °F (77 °C), unconverted starch (and other undesirable substances like excess tannins) can be released from the grains and contaminate the wort. The solution to this problem is simply to lauter with cooler water.

If your yeast strain does not flocculate well, you can try fining with gelatin or filtering to clarify the beer. If the cause of the haze is a microbial intruder, the flavor of the beer is likely to be pretty bad, in which case clarity is no longer an important issue!

Unexpected final gravities: The final gravity of the beer may be farther from your target than you had hoped. If the measured gravity is too low the cause could be too low a temperature during the saccharification rest (lower temperatures result in more fermentable worts). The next time you brew the recipe, rest at a higher saccharification temperature and be sure the temperature is relatively even throughout the mash.

If the final gravity is much lower than expected and the beer has some phenolic off-aromas, wild yeast is likely the culprit. Control of sanitation is beyond the scope of this article, but it is important to know that certain problems have multiple causes. It will not be necessary to alter your mash schedule if you determine that wild yeast are the reason your beer is over-attenuated.

A high final gravity can indicate that the saccharification temperature of the mash was too high. Beta-amylase, which produces the majority of fermentable sugars in the mash, is rapidly denatured at temperatures over 158 °F (70 °C). A wort produced at 158 °F or higher will therefore be rich with unfermentable dextrins. Reduce your saccharification temperature the next time you brew the recipe to achieve greater attenuation.

Too high a final gravity may also indicate a stuck fermentation. The most common reasons for stuck fermentation are either underpitching or underaerating the wort and too low a fermentation temperature. Fermentation control is beyond the scope of this article, but it should be said that if you are going to all the trouble of making an all-grain beer you should pitch a large quantity of healthy yeast to ensure a sound fermentation.

See the tip on page 13 for an easy way to adjust your preboil volume to achieve the desired gravity. For information on using forced fermentations to predict the final gravity of your beer, read Louis Bonham's article cited in Further Reading.