I was doing a little research the other day and came across the Sabco RIMS-WIZARD. Their website claims that stirring of the mash is not recommended. What is your opinion on stirring of the mash? Is there much information available?
Frank Uhi
Brockay, Pennsylvania

There is indeed much information about mash stirring and the use of agitated mash mixers is the norm in modern commercial breweries. The primary reason for stirring the mash is to provide uniformity when heating the mash. Brewers who employ step mashing, sometimes referred to as upward infusion mashing, double mashing and decoction mashing all use mash mixers. I think that the history of brewing clearly shows that mash mixers were first developed to deal with the challenge of uniform heating.
   
A side benefit to stirring the mash is improved yield. In large mash mixers another consequence to mixing can be shear damage from aggressive mixer designs and/or the use of baffles in mash mixers. Companies that design and build equipment for breweries have addressed the problem of shear damage by using low shear mash agitators designed to pump the mash down to the center of the mash mixer bottom. The mash then flows across the bottom and up the sides; since the mash mixer bottom and side walls are typically steam heated this flow pattern is ideal for heat transfer. Although many mixer designs are touted by equipment manufacturers, they all work on similar design premises.
   
When mash mixers are used during mashing there is always a separate wort separation device, be it a lauter tun, mash filter or the now obsolete Strainmaster once used in many of the Anheuser-Busch breweries. All of the devices are designed to separate clear wort from the grain bed. A common feature of all of these devices is that the mash is not stirred during wort separation. Despite the appearance of a lauter tun raking machine, it does not stir the mash when properly designed and used, rather it gently cuts and lifts the grain bed while very, very slowly rotating.
   
The traditional infusion mash system is totally different than the mashing systems I just mentioned. In an infusion mash tun the malt and water are mixed during mash in, the mash is distributed by the brewer using a mash paddle (or mechanical device in larger mash tuns) and the mash is held without heating during enzymatic conversion. After conversion is complete, the false bottom of the mash tun allows wort separation to occur in the same vessel. Infusion mash beds are not disturbed during the mash rest and there
is no raking machine in the traditional mash tun.
   
The RIMS (Recirculated Infusion Mash System) method of mashing is based on infusion mashing in that the mash is not stirred during mashing and that the mash vessel is also used during wort separation. The thing that distinguishes RIMS from traditional infusion mashing is mash heating, and with RIMS mashing the heating is made possible by the use of a wort recirculation pump and external wort heater. My guess is that mash stirring is not recommended because excessive stirring could lead to problems with wort separation after the mash is complete.
   
In the 5-gallon (19-L) pilot brewery at UC-Davis where my fellow graduate students and I brewed as much as we possibly could, we had a “lauter tun” located below the mash mixer. When doing stirred mashes, the mash was gravity transferred from the mixer to the “lauter tun” (no raking machine). When we did infusion mashes we would simply mash into the “lauter tun” and contrary to what is often written about infusion mashes we would periodically give the mash a gentle stir and we never had any problems with a stuck bed or wort turbidity issues that extended beyond the recirculation of wort prior to wort collection.
   
For the last 13 years I have formulated numerous styles of ales and lagers at Springfield Brewing Company and all of these beers have been brewed using a mash mixer and a lauter tun. So stirred mashing is what I know best. What I can attest to is very good extract yield, excellent repeatability and freedom to brew just about anything we can dream up.

I’m currently all-grain brewing, and I’ve been getting a rather high evaporation rate. In fact, I have learned not to go by percentage any more but with my equipment. I seem to boil off about 7–8 liters (~2 gal.) in an hour. That makes my SG of the wort very high. I was aiming for 1.055 but am getting about 1.062 after cooling down. Is it okay to add water to bring it to 1.055 levels or nearer to 5 gallons?
John Weiht
Singapore

Knowing the evaporation rate of your equipment is important when trying to brew beer to a target original gravity. There a few things that you can consider to solve the problem you are having. Beginning with more water is one way that you can compensate for your high rate of evaporation. If you choose to do this I would collect wort from the mash bed until the gravity falls to about 2 °Plato or a specific gravity of 1.008. Collecting low gravity wort leads to grainy, astringent flavors in the finished beer. So if you want more volume before the onset of boiling I would simply add water to the kettle instead of running extra sparge water through the grain bed.
   
Another option is to add water to the hot wort following boiling. At Springfield Brewing Company we actually use this method as our standard method of brewing so that we can adjust our wort gravity to specification for our brews. This also allows us to produce more wort since we can brew slightly higher gravity wort and dilute after boiling. Since kettles can only boil so much wort, adding water after boiling is one way to boost wort volume.
   
Adding water after the boil is a way of brewing more beer and may make sense depending on the size of your kettle. Adding extra water to the wort before the boil, however, may not be required if you can regulate the heat that you are applying to the wort during boiling. In fact, if this problem occurs in a commercial brewery it is really a problem of energy waste. Most beers these days have a total evaporation during boiling between 4-8%. The trend is moving more toward 4% or less in new kettles, but for some beers this evaporation rate is too low unless the kettle is really designed to strip DMS during or after boiling using some type of stripper.
   
From what you describe you are removing more than 20% of the volume during boiling. This is really excessive and for most beers you are not gaining anything with this high rate of evaporation. In fact, if you like brewing some of the lighter styles this amount of evaporation is probably leading to higher colors and is likely lending some flavors that would be good to not have. I would turn down the heat during boiling to bring your total evaporation down closer to 10-12%. If you have flavors like DMS in the finished beer you could boil a bit harder, but I do not think this will be the case.
   
All the methods described above can be used to hit your target gravity. I would choose the method that makes the most sense for your needs. “Most sense” can also be interpreted as best tasting beer. Good luck!