I've done 2 partial mashes and have ingredients ready to go for my 3rd. My first partial mash came out perfect, while my 2nd had an original gravity much lower than the target(1.060 vs 1.092). So the first thing I want to do is explain my process for my last partial mash that didn't reach the target OG.
I have a 3 gallon mash tun that is a converted water cooler pictured below. I had 4.75lbs of grain so I used 1.25qts/lb to get 1.484 gallons to mash with. I placed my grains in a paint strainer and placed them into my tun. I heated the water up to 174 in an attempt to reach a mash temp of 155. I poured the water over the grains than used a paddle to push and prod the grains to try and make sure their weren't any pockets that weren't coming in contact with the water. I screwed the lid on and covered it with a blanket. The instructions called for 45mins.
I then pulled a few pints and recirculated it into the top of the tun until it was clear. I then drained the tun into my 8 gallon brew pot. (The brew pot had 3.5 gallons of cold water in it which I figured would make a little over 6 gallons when I got the first runnings and sparged. I then heated up an equal amount of water as the mash (1.484 gallons) to 170 and poured it into the tun. I prodded the grain a little bit and then drained that into the brew pot. I was now up to my desired preboil water volume and went ahead and brought it up to boiling, removed from heat, added the liquid extract, boiled and started adding hop additions.
So I can think of a few mistakes I probably made. When I took the temp of the mash after 45 mins it was only 144. So I'm thinking it was too cool of a temp for the 45 mins to extract all of the sugars. I did a test on my cooler with just water this week and it loses about 10 degrees over an hour. The major culprit I think is the lid. It's very thin and gets very hot unlike the rest of the tun. Is there anyway to fix this? Also I think I'm supposed to put the water in the tun and then submerge the grains...is this correct? Also I think I should have been adding the wort I made in the tun to water that is being brought up to a boil, is this also correct?
When it comes to the batch sparging, I used the some amount of water I did for the mash. When it comes to all grain it looks like you batch sparge with the amount of water you need to bring the brew pot up to the pre-boil water volume. How much should you use when partial mashing? I think I read you don't want to use too much because it will extract tannins from the grain.
Could someone help me out with my questions and point out any other mistakes I made. Thanks a ton, I greatly appreciate your help.