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:
Here's all the parts I'll use to make the mash tun. Everything can be purchased at Home Depot with the exception of the cooler. That was a yard sale score. The only thing not pictured is a couple wire ties and the rubber gasket from the cooler.
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.
The stainless steal braid I'm using is a toilet supply tube. I hacked off both ends and pulled out the rubber tubing. The braid will act as a filter for the mash tun allowing the wort pass through and leaving the spent grains behind. I've made a spiral coil from copper wire to line the inside of the braid. My hope is this will prevent the tube from crushing due to the weight of the grains. This could cause a stuck sparge. It's a little challenging to get the spiral through because the braid' s like a Chinese finger trap. My fingers bled from the frayed stainless steel. Take my advise and use something to feed the spiral through like a wire tie as pictured above.
After the wire is through I secured the one end with a brass nut and wire tie. This will not only force the liquid through the braid by closing off the end, but will also provide enough weight to keep the braid on the bottom of the tun when stirring.
Before attaching the fittings I've made sure to wrap the threads with teflon tape to avoid them getting stuck together. Wrap it the same way the threads will screw together.
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.
Here's the braid secured. The brass fitting wasattached to the braid with wire ties just like the bolt.
All secured tightly and ready to use.
Success! No leaks and everything is functioning properly.I'm very pleased with the way this turned out. The total cost was right around $30. I think it should be durable enough to last for some time and also large enough to do some nice sized partial mashes (SPOILER ALERT: It worked great on it's inaugural run!). Since the cooler is only 5 gallons I'll have to upgrade again for all grain when the time comes, but this should be fun in the meantime.
Ingenious and thrifty, all at the same time!
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