Brewery Equipment: Mash/Lauter Tun Insulation

Since our efficiency was so low on the first all-grain brew, I did some research to see how we could improve our efficiency and also how to reduce the sweetness in the finished beer. After reading the How to Brew website, The Complete Joy of Homebrewing book and a couple articles I read on the web, I have decided that on our next brew we will allow the mash to rest at 3 temperatures; 30 min at 122, 20 min at 150 and 15 min at 158.

I would rather not have to apply heat during the rests since it makes the time too busy, and it is hard to keep the mash within a few degrees of the target temperature. I noticed on the Texan Brew site that they insulated some of their kegs so I decided to insulate our mash keg. I found some duct insulation at home depot that is coated with aluminum and rated at 3R. After installing the insulation and taping it up I did an experiment to determine 3 things:

1. Would the insulation burst into flames?
2. Would it keep the water at temperature for 30 minutes?
3. Did the insulation make any difference?

To answer those questions I filled the insulated mash keg and the uninsulated brew keg up with ~3 gallons of water and brought them up to 122 degrees. I kept them both covered, and opened them up every 5 minutes and stirred them with the mash paddle (recommended for step mashes) and then took the water temperature with the following results:

I charted the results after correcting the data to the same start temperature, in the actual experiment the uninsulated keg started 4 degrees higher. Some interesting observations:

1. The temperature rose after removing heat for about 5 minutes then began to drop off.
   
2. The uninsulated keg temperature dropped twice as fast from peak temperature as the insulated keg.
3. The insulated keg was able to maintain temp. to within 3 degrees(F) for 30 minutes.
   
4. The "metallic" tape I purchased melted off the bottom of the insulation, I replaced it with aluminum.

After seeing the tape melt off, I decided to test the insulation to see if it was flammable. It was. I experimented and determined that it would not ignite from the heat of the keg, but it could begin to burn if directly exposed to gases that were hot enough. Flame on the aluminum shield did not cause it to ignite however.

When installing the insulation, I left 1 inch between the bottom of the insulation and the start of the ring surrounding the bottom of the keg so the insulation that was in contact with the keg wasn't going to get hotter than the mash, but the hot gases rushing up the side could ignite the exposed bottom portion. To provide a shield against the gases, I cut some excess insulation into a 3 inch strip and removed the insulation, leaving only the aluminum with some remaining glue. I installed it in place of the melted tape around the bottom of the keg.

Overall I think this will make step-mashing quite a bit easier, and will reduce the use of the propane as well. I will wait to see if it performs well for the next few brews before I insulate the Brew Keg and the HLT though.

Update: Nov, 2009 - I now use this as my brew kettle, and use a 10 gallon rubbermaid cooler as my mash tun. It holds heat much better and holds up to 20 lbs of grist. To increase temperatures in step mashes, I draw off 5 quarts of liquor, bring it to a boil in a 6 quart pot and return it to the mash.