Pros, Cons, and Myths

What are the Advantages of a RIMS?

Many peoples first reaction to a RIMS is that it is complicated. However, the reality is that the most complicated part by far is building it. And if you skip over the automated electronics or buy them pre-made (more info on this below), then the construction is not that difficult either. Once you have yours built, the mashing process is simple and provides for many benefits:

  1. Faster, more efficient conversion: As you've probably seen in many chemistry labs, chemists often use mechanical mixing to improve both the speed and the yield of the reaction. The enzyme reactions that are occurring in your mash are nothing more than complicated chemical reactions which can also benefit from mechanical mixing. While reports of increase in yield (better extraction efficiencies) are debatable, many RIMS users report complete starch conversion in 10 - 15 minutes. (Note: this does not mean that the entire mashing process only takes 10-15 minutes. Starch conversion does occur this quickly, but there is still plenty of other reactions that need to take place before your mash is complete. Starch conversion is just one of many steps.)

  2. More even and controlled heat distribution: Mixing causes more even heat distribution within the grain bed. Depending on your dough-in technique and your mash tun insulation, you may have temperature gradients within your grain bed. The mixing provided by the RIMS removes these temperature gradients thus allowing for more accurate control of the enzyme activity that you are attempting to favor.

    Zymurgy photo

  3. Improved wort clarity. The grain bed is set immediately and particles are cleared/filtered within first few minutes of mash-in. The photo to the right was provided by Kerry Hauptli (owner of BrewCraft, Ltd manufacturer of RIMS related equipment) which he used in his RIMS related Zymurgy article to demonstrate how clear the wort becomes. Thanks for the photo, Kerry!

  4. Saves time. Besides enhanced speed of mashing, you no longer need to manually recirculate the first runnings.

  5. Control and repeatability. You can more easily duplicate a beer from batch to batch because you have more accurate control of the mash temperature.

  6. Accurate control of mashing temperatures. In fact I always try to err on the low side when I mash in because I can always boost the temperature up to my target.

  7. Complex mashing techniques are more easily implemented. With a RIMS, you can easily step from one temperature to the next without the need for stirring, turning a stove on and off, or boiling liquid and mixing it in with your mash to boost the temperature.

  8. And the number one reason to build a RIMS............ Building brewing gadgets is fun!!!!

What are the Disadvantages of a RIMS?

I guess it would only be fair to discuss the disadvantages, although I think they are few and minor.

  1. Expense. Pumps, plumbing, and (optional) electronic controls will cost a few hundred dollars, although surplus suppliers can save you some money.

  2. Space. A complete three tier system takes up some space, although you don't necessarily have to build a such a system. Consider building a stand-alone RIMS unit (pump, heating element and controls) in a separate small unit to use with your existing system. And if you already have a three-tier system, then adding a RIMS to it will not require any additional space. (Many responders have pointed out that it is actually the all-grain setup that takes up the extra space, not the RIMS. The RIMS components (pump, heating element, etc.) actually require very little space. Good point!)

  3. Hot Side Aeration (HSA). HSA is the effect of oxidizing your wort by splashing air into it when it is hot (160 °F or hotter). Oxygen mixed with hot wort causes chemical reactions that bind the oxygen with the wort which essentially causes a delayed oxidation of your beer. The effect is similar to splashing air (oxygen) into your fermented beer which causes stale, cardboardy flavors. The main concern with RIMS is that you are constantly recirculating hot wort that is close to the temperature where it is most vulnerable to HSA, so you must be careful not to splash it. However, I believe a properly designed RIMS should have no problem with HSA. Simply make sure that all tubing is well sealed so that air is not sucked into the tubing during recirculation and also be sure to gently return the wort to the top of the grain bed.

Myths of the RIMS

Besides that valid pros and cons discussed above, there are also a few myths circulating around about RIMS. I'm not sure how or why these myths arise, but here's my attempt to put them to rest:

  1. Astringency. The claim of astringency from RIMS systems comes from two different areas. First, the above mentioned HSA has been known to create what some describe as an astringent quality to beer, but if your RIMS is properly designed and you avoid HSA then this should not be a problem. Second, some RIMS disbelievers will tell you that the recirculation process will extract tannins from the grain husks and cause astringency in your beer. This has never been found to be the case and is probably the result of speculation by non-RIMS users who are confusing the extraction of tannins during the later stages of sparging (once the wort has thinned and the pH has risen) with the recirculation process. Any sparging process is subject to this happening during the sparge and is totally independent of a RIMS. Since the wort is not thinning during RIMS recirculation, the pH doesn't rise and thus tannins are not extracted.

  2. RIMS mashing makes for thin or weakly flavored beers. This myth arises because of the thought that the length of time required to raise the mash from the low temperatures of protein rests (120°F) up to the higher temperatures of the saccharrification rest (155°F) is too long. The extra time spent in this transition zone supposedly creates a thinner beer. In theory, this could happen. But a properly designed RIMS should be able to easily raise the temp of the mash 1°F to 1.5°F per minute. Thus this approximately 30°F transition takes only 20 minutes. This is just not enough time to cause substantial starch conversion. In fact it takes about 75-90 minutes at 149°F to result in full conversion. Plus, malt starch does not fully gelatinize until it reaches approximately 149°F. Until this happens, most of the malt starch is just not available for conversion, and no mashing really takes place