The equipment for decoction mashing requires vessels that can be heated without scorching the grains. There are numerous ways to go about it, but the easiest is to equip either gas burners or electric heating elements outside the pots. For those who want to take it to the next level, steam jackets or tubes around the perimeter of the kettle — would be the finest solution. It will require quite a bit of handy-work though.
I’ve settled for electric heating via the Hendi 3500 M induction plates — which are up to 50% more energy-efficient and very responsive. Together with Armaflex insulation, they can bring a 70 litre Contacto pot to a rolling boil without much fuss. The evaporation rate in this case is nearly 10.4% which is more than enough.
The other challenging aspect is to transfer the boiled grain at temperatures around 80-95°C. Simple scooping works best for the batch sizes involved here. However, once going towards the 0.5hl brew length I’d say that a positive displacement pump (they are over £1400.-) is pretty much a must.
Scooping isn’t so bad. In fact it allows for very mellow transfer with little risk of scorching the grains if the main mash is stirred (carefully) after the hot grains are added back. This is to avoid scorching an unnecessary large amount of enzymes.
Generally, the decoctions pulled are at a 2:1 water to grist ratio and make up about 30-33% of the total volume. I’ve stopped working out the required volume. It’s futile. Any excess can be re-introduced later on once it cooled down. But this rarely happens. It’s always better aiming for a little more in this case. Also, these calculations assume optimal conditions (which we don’t have). If you want to work it out, then I suggest not using 100°C for the temperature of the liquid transferred. 80°C is a much better and more realistic figure (the heat drops quite fast once the plates are switched off). Transfer should be complete within 10 minutes.
Either way, one is well-advised pulling 30-33% of the mash as decoction. The grain bed should look something like in the picture below — which more or less equates to the correct water to grist ratio.
This is a debated subject. Although I sometimes wonder why. Introducing oxygen during the hot-side part of the process is generally a bad idea, even though it won’t impact on flavour. However, it will impact on the colour of the resulting beer.
For most, this won’t matter much. But the recipe formulation for Bavarian Helles is such that it every possible avenue is pursued in order to make the brightest, full-bodied beer with a nice malty nose. Unnecessarily introducing extra oxygen during the mashing process won’t result in a Helles, but more in a beer resembling a Märzen or Vienna. I always have this in mind when mashing and take the extra little time to transfer grains and hot liquid carefully. This is also why I filter the wort cold, and not hot like some home brewers do. It’s not as “dangerous” like some proclaim. Basic sanitary practices are totally sufficient. Any oxygen taken up will be gratefully consumed by the awaiting yeast later on.
Some day I may build motorised agitators and may even find a suitable pump for transferring the decoctions. But these are tweaks and it’s possible to make a very yummy brew without those gimmicks… The volume we are talking here won’t justify the expense.