A Practical Treatise on Brewing/Appendix/Saccharometer
SACCHAROMETER.
All Saccharometers now in use are graduated to a scale of barrels containing 36 imperial gallons each. If gravities, therefore, be reckoned by barrels containing only 32 gallons, the calculations must be very erroneous. An Irish barrel contains only 32 gallons, and yet many brewers in Ireland, in calculating the gravities obtained from the malt, multiply by their own barrels, and thus persuade themselves that they are getting much greater lengths than the malt could possibly produce. Thus, suppose brewing 30 qrs. of malt, they have 100 Irish barrels in the gyle-tun at 30 lbs. gravity per Long’s instrument (which is equal to 83.4 by Bate’s), they reckon they have 3,000 lbs., or 100 lbs. per qr. Instead of this, however, they have 400 gallons less than 100 barrels, leaving only within a fraction of 89 imperial barrels; they ought, therefore, to multiply 89 by 30, which would make only 2,670, instead of 3,000 lbs. Divide, therefore, 2,670 by 30, which will give the true gravity per qr., or 89 lbs., instead of 100 per Long’s instrument (or 247.4 by Allan’s or Bates’).
Saccharometers which have been long in use will, from the friction used in cleaning them, become lighter, and consequently show considerably higher gravities than those actually produced. This is a point seldom thought of. They should, therefore, be occasionally tried by dipping them in the water used for brewing, at a temperature of 60°, when, if the water do not cut the stem of the instrument at the proper point indicated as the water line, the instrument should be adjusted. Many Irish brewers, by calculating in the above-mentioned erroneous manner, are led to believe that their practice must be far superior to that pursued in the Sister Island, or that their malt must be of better quality. Neither of which, however, is the case.