By incidents, I understand such causes as effect either the malt, the water, or the mash, during the time the brewing is carrying on, so as to occasion their heat to differ from what is determined by calculation. As these might frequently be a reason of disappointment, an inquiry into their number and effects will not only furnish means to prevent and rectify the errors they occasion, but also serve to confirm this practice.
In our researches on the volume of malt, some notice was taken of the increase of bodies by heat, and the loss occasioned by evaporation. Water, when on the point of ebullition, occupies the largest space it is susceptible of; but contracting again, when cold water is added to it, the true volume of both, when mixed together, remains uncertain, and may cause a difference between the calculated and real degree of heat. This cause, however, producing an effect opposite to, and balanced in part by evaporation, becomes so inconsiderable, as hardly to deserve any farther consideration.
Water, just on the point of ebullition, may be esteemed heated to 212 degrees. Though, by the continuation of the fire, or by any other cause[30], the heat never goes beyond this, yet was cold water added to that, which violently boils, the degree expected from the mixture would be exceeded; for the cold water absorbing the superfluous quantity of fire, which otherwise flies off, becomes hot itself, and frustrates the intent. The time, therefore, of adding the cold water to the hot is immediately before the ebullition begins, or when it is just ended; and in proportion as we deviate from this practice, the heat in the extract will differ from the calculated degree.
The water, for every mash, should, as near as possible, be got ready to boil, and be cooled in just before it is to be used. A liquor, which remains a long time after the ebullition is over, and the fire has been damped up, loses part of its heat, if cold water is applied to it, the effect cannot be the same as it would have been at first. On the contrary, if the liquor is got ready too soon, and cold water immediately added to it, in order to gain the proper degree of temperature, by leaving the mixture long together, though the fire is stopped up, more heat than necessary will be received from the copper and brickwork, especially if the utensils are large. In both cases, the degree in the extract will not answer the intent.
The effect of effervescence next deserves our consideration, but this takes place only when the water first comes in contact with the malt. Germinated grains must, to become malt, be dried so, that their particles are made to recede from one another, thus deprived of the parts, to which their union was due, when they come in contact with other bodies, (as water) they strongly attract the unitive particles they want, and excite an intestine motion, which generates heat. This motion and this heat are more active in proportion as the grain has more strongly been impressed by fire, and the extracting water is hotter.
A large quantity of liquor applied to the grist is less heated than a small one, by the power of effervescence. The least quantity of water, necessary to shew that power, must be just so much as the malt requires to be saturated, which we have seen to be double the volume of the grain. When more water than this is applied to the grist, the real effervescing heat is by so much lessened, being dispersed in more than a sufficient space.
A table shewing the heat of effervescence for every degree of dryness in the malt, can only be formed from observations. To apply this table to practice, and to find out, for any quantity of water used in the first mash, the degrees of heat produced by effervescence, three times the volume of the grist must be multiplied by the number expressing the effervescing heat for malt of such a degree of dryness, and this produce be divided by the real volume of the whole mash.
A TABLE shewing the heat occasioned by the effervescing of malt, for its several degrees of dryness.
| Dryness of malt. | Heat of effervescence. |
| 119° | 0 |
| 124 | 3½ |
| 129 | 7 |
| 134 | 10½ |
| 138 | 14 |
| 143 | 17½ |
| 148 | 21 |
| 152 | 24½ |
| 157 | 28 |
| 162 | 31 |
| 167 | 35 |
| 171 | 38½ |
| 176 | 40 |