So what is partial mash brewing? It's an additional step where the homebrewer makes a portion of the wort from scratch by mashing grains. This is the same process as an all grain brewer, except instead of making all the wort from scratch the brewer still relies on some extract.
In a nutshell, the mash process is mixing the milled grains with a ratio of water at a certain temperature for a predetermined amount of time. The brewer then separates the wort from the spent grains, which is called lautering. Mashing allows the enzymes from the grains to convert starches to sugars that will later be fermented by the yeast. The final step is to sparge, meaning rinse the grains with water usually at a higher temperature and collect the liquid. Sparging stops the enzymes from converting starches. From there it's off to boil.
There's different techniques to mash, all of which affect the final product for better or worse. In order to successfully mash you need a mash tun. They can be bought at local homebrew stores prefabricated, but I decided to make my own. There is a ton of resources on how to make your own on homebrewtalk.com. A little research definitely went a long way. Here's what I came up with:
I decided to use brass fittings since it's a cheap alternative to stainless steel. I've read that brass can contain a small amount of surface lead, which doesn't exactly lend itself kindly to brewing. Fortunately there is a process to cleanse brass called pickling. You need to prepare a solution of two parts vinegar/one part hydrogen peroxide and let the brass soak for about 5 minutes. It's important to remove the brass and rinse before it turns a greenish blue. I had the brass begin to turn this color so I had to redo the process. In the end everything that will come in contact with the wort looked good to me.
I needed to attach some washers so I could fully tighten everything. I also used a rubber washer and the original rubber gasket from the cooler to ensure it didn't leak.
All secured tightly and ready to use.