Brewing Basics Mashing and Lautering
Here in south Africa we have do not have the luxury of being able to by our equipment off the shelf but rely instead on the technically minded to "improvise" equipment using commonly available house hold items in the strangest of ways. To get the best the best "design" it helps to understand what happens in the equipment and what has been fount to work by others and comparing this to standard industry practices. Home brewing we have the advantage of using non-perfect arangements as time and efficiency can easily be compensated for with out aggravating the been counters.
Mashing is the process in which the starches in the malt is broken down by enzymes into monosacarides and disacarides on which yeast can feed and convert into alcohol, carbondioxide and other flavour compounds which we know as beer.
Lautering is the process in which the sweet sugary solution is separated from the husks by filtration and washing. A separate vessel can be used for each process or a combined mash and lauter tun can be used. Most home brewers use a combined mash and lauter tun which works well for single step infusion mashes. The single vessel system becomes impractical on a larger scale as the large diameter and low height required on a laughter tun makes it unsuitable as a mash tun due to the difficulty to insulate the vessel and heat the grain evenly. During the hot phase of the brewing process air must not come into contact with the mash or wort, it is almost impossible to do this during the transfer of wort from the mash tun to the laughter tun in a home brewery, a single vessel is thus preferable. Another up side to the single vessel system is that the capital costs are lower. Also as will be seen when we get to the calculations the grain depth to brew volume on a home brew scale requires a mash tun and laughter tun to have similar dimensions.
The simplest method to make a mash tun is to buy two buckets that will fit inside each other. The inner bucket you drill hundreds of 2,8 mm holes at approximately 10 mm spacing in the botom of the bucket. On the outer bucket drill a larger hole through the side of the bucket at the botom to fit a tap. Insulate the outer bucket by wraping a camping mattress (or similar insulating material) around it - you now have a single step infusion mash tun. The alternative is to get hold of an old picnic cooler and some ½ inch copper tubing, 3 solder type 'T' pieces and 6 90° elbows. Cut 3 lengths (1 down each side and one in the middle) of copper tubing about 50mm shorter than the inside length of the cooler box and cut slots in them at 10mm intervals with a hack saw blade. Cut 4 short pieces that will join the outer long lengths to the centre one with the elbows and "t" pieces. Do not solder any of the manifold pieces as you will need to clean the pipes fairly frequently. At one end make a riser assembly which must be soldered as it will be used to siphon the wort over the top of the cooler box sides. The effectiveness of the two systems is discussed fully in Brewing Techniques of July/August 1995 under the title of Fluid Dynamics - A simple key to the mastery of efficient lautering by John Palmer and Paul Prozinsky. Either system will produce an adequate method to collect the wort.
The main objective when designing a Lt is to prevent the formation of preferential flow. Preferential flow is affected by both the mashing method (if using a combined Mash and Lauter tun) and the design of the tun which affects the flow velocity. Dr. Narziss of Weihenstephen recommends that he velocity of the wort should not exceed 0,732 litters per min per m2 (0.18 gal/min ft2). From this value we can calculate the number of holes or slots that are required. Also, the grain bed should be between 250 mm and 450 mm. This holds true regardless of the amount of beer being brewed thus if 20 l of beer is being brewed the depth of the grain bead will be equal to or deeper than the diameter. However, if the volume is a few hundred hecto litters the depth will still be between 250 and 450 mm but the diameter will be a few meters, a very cumbersome mash. Another slightly simpler method of determining the size of a LT is to use the ratio of 170kg grist per m2. The following diagrams show how the various lauter tuns draw the wort through the grains. The light grey areas are grains that have been rinsed and the darker areas show grains partially rinsed or not rinsed at all. The left hand diagrams are the top view and the right hand diagrams are the front view.