This is where the playing around and thinking outside the square bit come into play... Normally, you would add the malt pipe and bottom filter plate, then add your water and heat it. Once at strike tem, you would stir in the grain and then add your top filter plate and lock it all into place. With this method I have squeezed in just under 12kg of grain and with all that grain, got away with having enough water to complete a circuit for the mash to knock out a 35L batch. This works out to be about 1.077-78 OG, and with proper attenuation, is going to give me an ~8% beer. Not something I'm going to brew 35L of every week...
BUT...
There is more...
In the past, I have been known to put the malt pipe in, put in the bottom filter plate, tip in my grist, give it a shake to settle it all down, tip in a bit more, repeat, repeat blah blah until I've squeezed a tad under 13 kg of grain in there. Then I add the top filter plate, upside down so the little tube on it goes down instead of up, and then fill with my water. Now there a a couple of lessons I've learnt here...
First, the idea of the little tube on the filter plate is to make the filter plate sit about 30mm below the top of the malt pipe so when the grain expands a little, and the filter plate flexes a little, the grain still stays entrapped in the malt pipe. When it's turned over the other way, when the plate flexes, a little gap can open and let some grain out... so on the rare occasion that I am doing this, I put a smaller packer between the filter plate and the retaining bar to keep it just below the top of the malt pipe.
The astute among you that are still following on are probably about to open the quick reply box and start a tirade about grain bed compaction and doughballs... well the doughball thing is not so bad because I have a stiff bit of wire that I put in through the holes in the filter plate about a million times to break up the mash. I'm not sure it's such an issue with a constant recirculation system anyway. And I have gotten the same efficiencies as I used to when I had a conventional style MT with a standard FB, and also similar to when I had an esky with a manifold.
Doing the second method can be a bit of a juggle though... when doing this, it's only an educated guess what my pre boil gravity will be, and then a couple of quick calculations as to what the post boil will be so I can calculate the amount of hops and adjust IBU's etc.. but like I said, I only do this once in a blue moon when I'm doing a huge beer. I have used this method to get a RIS out at a tad over 1.097 and ended up with about 26L after a 2 hour boil. With a couple of sugar additions in the ferment, it was pretty heart warming stuff...
So yeah, in short, you can do a high gravity beer, but it's just a little trickier than if you had a big arse esky... And honestly, if I wanted to do a 18L batch of 13% Belgian Strong or a 15% Barley Wine, I'd just mash in my old esky and run it into my braumeister to boil.
