When I first began learning about mashing from a friend, we used his setup which employed a plastic bucket and a thick, insulated sleeve slipped over the bucket. We rarely had problems hitting our target mash temperature. Like many others making the transition to all-grain brewing, when I purchased my own equipment, I chose a cylindrical Igloo/Rubbermaid/Gott cooler for my mash tun. In my new cooler-based system, however, I found myself struggling to achieve the same consistency. Most brew days I found myself adjusting the mash with cold or hot water, both of which I had to have prepared, because my mash ended up too high or too low after the initial infusion.
Even after many attempts at recalibrating my equipment and brewing software, I have still found myself missing my mash temperature more times than hitting it. Usually the obvious candidate for the problem’s source was the mash tun temperature. My brew day starts with me pulling my equipment out of the garage as I begin heating up my strike water. At the time of this writing, snow has been on the ground for over a week, and my mash tun is really cold. If I grab my mash tun as soon as the strike water is ready (or even soon before starting to heat up my strike water), the temperature in the cavity of the cooler will be different than that in the cooler walls. If I then rely on the calculated temperature from my brewing software, when I dough-in, the cooler will suck heat out of the finite amount held by the strike water and will decrease the amount available to be absorbed by the grain.
Brewing software does a good job with computing the temperature of your strike water, but requires accurate data across many variables including grain temperature, total grain mass, grain moisture content, mash tun temperature, mash tun weight, and mash tun material (e.g. plastic, stainless steel). If inaccurate information is used in the calculation, the computed results won’t do you any good. Most homebrewers I’ve spoken with do not adjust all the low-level information once they get their software set up, and as the saying goes, garbage in, garbage out.
I have encountered several popular approaches homebrewers use to address this issue:
- Pre-heat your mash tun with hot water so the mash tun does not suck energy from your strike water.
- Bring your mash tun to your brew location the night before so the entire mash tun has enough time to come to rest at the ambient temperature of your brew location.
- Heat the strike water to temperatures slightly higher than the computed value, allowing the extra heat to warm up the walls of the cooler. Then stir the water vigorously until it reaches the calculated dough-in temperature.
After trying all of the methods above, overheating the strike water provides me with the most consistent ability to hit my target mash temperatures at the expense of about 20 minutes added to my brew day. Allowing your cooler to warm up to the measurable ambient temperature of your brewing area got me closer to consistently hitting my target, but I still found myself missing my target temperatures. This may be due to not having the correct value in place for my mash tun’s thermal mass (the capacity of a body to store heat) or some other setting. However, by using the last method, I ensure the entire mash tun (water and all) is at the target temperature and ready to give it’s heat up to the grain I introduce when I dough in.
Being able to reliably hit your mash temperature is a cornerstone for achieving the beer envisioned when your recipe was created. Find a method that works for you and use it every time you brew.