Using hot rocks for caramelization?

I have heard it is possible to heat granite rocks until they are red hot, use them to start the boil and also in the boil. This results in some caramelization of the sugars on the rocks, which you then put into the primary fermenter. I can't say I really plan on doing anything like this, it sounds a little dangerous, but has anyone done this?

I've never done it myself, but I saw a BYO recipe that included this particular method for caramelization. ymmv.

Stonehenge Stein Beer
When you wish for new brewing gear, do you ever wish for metamorphic rocks? You might after seeing this recipe. Here’s a recipe for steinbier — a beer whose wort is heated by hot stones. Heat from the rocks boils the wort and caramelizes sugars they directly contact. To brew this beer, you will need at least a 10 gallon pot, a stainless steel basket and heat resistant tongs to handle the rocks. For safety purposes, it would be best to get a friend to help you. When moving the rock-filled basket into the wort, suspend it by the basket handle from the middle of a pole, held on each end by one brewer. So here’s the recipe — do you have the stones to try it?

Ingredients
5.0 lbs. (2.3 kg) 2-row pale malt
5.5 lbs. (2.5 kg) Munich malt
0.5 lbs. (0.23 kg) crystal malt (40 °L)
6 AAU Hallertau hops (60 mins)
(1.5 oz./43 g of 4% alpha acids)
10-15 fist-sized chunks of granite
1 tsp. Irish moss
White Labs WLP002 (English Ale) yeast (1 qt/1 L starter)
0.75 cups corn sugar (for priming)

Step by Step
Start a hardwood fire in a large grill. Let fire burn down to coals and place rocks in coals. Mash grains in 2.5 gallons (9.5 L) of water. Hold mash temperature at 150 °F (66 °C) for
60 minutes. Run off wort, then sparge with 170 °F (77 °C) water to yield 6 gallons (23 L) of wort. With heat-resistant tongs, remove 3 to 5 rocks from coals and place in a stainless steel basket. Whisk away any ash or embers from rocks with barbecue brush. Submerge basket with stones in wort. Boil for 90 minutes. Rotate rocks in kettle with those on the coals during entire boil period to maintain boil. Add hops with 60 minutes left in boil, Irish moss with 15 minutes left in boil. Cool wort, siphon to fermenter, aerate and pitch yeast. Place stones on a clean surface and allow them to cool. Store stones — wrapped in plastic wrap or in clean Tupperware-type containers — in refrigerator. After one week of primary fermentation, add rocks to sanitized bucket and rack beer on top of stones (which will be surrounded in a layer of caramelized sugar). Let condition for 2 weeks. Bottle or keg.

Make sure you DON'T get the rocks out of a river or creek. If they have any water contained inside them (micro-cracks, etc) the may explode when heated as the water converts to steam and expands. Possibly rather violently as well.
Ask me how I know!

bull8042 said:

Make sure you DON'T get the rocks out of a river or creek. If they have any water contained inside them (micro-cracks, etc) the may explode when heated as the water converts to steam and expands. Possibly rather violently as well.
Ask me how I know!

Click to expand...

I know that from my old sweat lodge days.....

POW!!!!!

Yeah, I'm aware that the rocks can explode. One time were sitting in a teepee and got a fire started in it. One of my friends had the idea of surrounding the fire with rocks from a lake and making a small pit, which he did. We started asking each other, "Hey, isn't it possible for these rocks to explode since they had water in them?" Not even 10 seconds later, BAM! and one exploded in half. We just started laughing (since no one got hurt) then proceeded to get the hell out of there.

December 23, 2003, I had the good fortune to help Larry Horwitz make a few barrels of steinbier. This was when he was head brewer at Manayunk Brewery & Restaurant and I was squaring away the brewhouse at Red Bell right up the street (alas, that brewery has been closed for years now).

It was basically an amber wort. IIRC, we ran five barrels into a stainless-steel trough and used a forge to heat this rather massive basket of the same sort of "lava rocks" you put in your gas barbecue grille. We had a big steel lever/fulcrum/thingy; we'd push down on one end, swing the basket into the forge, wait until it got quite hot, and swing it into the trough of wort. Never did get it to boil - not enough rocks, and it was December, fer cryin' out loud - but it did visibly darken the wort, presumably through Maillard reactions and caramelization.

I never did get to try that beer, dammit. But Larry said it was quite unique and tasty!

Cheers,

Bob

I read about this on Tastybrew

[ame]http://youtube.com/watch?v=CrIgxgG5f3Y[/ame]