We canned butter yesterday. Well, it isn't really canning, but it does get the butter in the jars and the jars seal and so you can keep your butter on the shelf with your other stored foods with no refrigeration for a few years. That's the theory. Lots of other folks have done this and presented all the info, so I'll skip typing out the actual steps but give you the links so you can go and read what they did, and what we did. It is nice to have 12 pints of butter stored (that's about 10 pounds worth). If you do this, you can buy butter when it's on sale and get a good price.
Michael's been after me for months to do this, so finally we did it. And it isn't hard or difficult, just messy. You can find clear instructions at Our Plain and Simple Life, or at the Just in Case blog. Both are similar with clear steps to take. Basically, the idea is to get both the jars hot in the oven, and the butter melted to boiling, then simmered, so all ingredients are hot. The jars are hot and must be handled carefully. The butter is greasy, and will spill out of the jars before they seal, but the jars must be shaken many times to get the butter to congeal, mixing the separated milk solids from the butter oil. If that's not clear, please go and read the instructions at those blogs and then what I've said here will make more sense.
We put the jars in a roasting pan in the oven, heated to 250 degrees. They have to be in there for 20 minutes before you start to fill them. During that 20 minutes you'll be melting your butter on the stove. Use the big pot you use for chili or stews, because 10 pounds of butter is a LOT of butter. The lids and rings go in a pot of simmering water on the stove. Once the butter has come to a boil and then simmered for 7-10 minutes, you fill the jars. Use a canning funnel and try not to spill the butter all over the place. Wipe the tops of the jars, then put on the lid and tighten the ring. Move the jar to the central shaking area (kitchen table) and ask the husband to shake them for you while you keep filling the jars. If you don't have an assistant, then you'll have to keep shaking the jars whilst filling the others. I imagine that could be a bit complicated.
Anyway, keep shaking the jars every few minutes. If/when butter spills out of the not-yet-sealed jars, wipe it off with a clean cloth (I used white vinegar on my cloth to help cut the grease of the butter). When jars are almost room-temperature, move them to the fridge, but keep shaking. Gradually the butter congeals in the jars and the jars seal. Leave the jars in the fridge for a while--hour or so. And that's it. You've "canned" butter.
Is it safe? I'm not entirely sure. According to the USDA, there are potential problems. Read about it over at an LDS forum here--scroll down a bit and you'll see the warnings. We went ahead and did it anyway, but I'll have those warnings in my mind and I'll be careful with that butter. The choice and the risk are yours too, if you choose to can butter.
I go and visit with Amish friends and farmers every week. They can food a lot, and don't always use mason jars and lids. And none of them seem to have problems with stored food spoilage. So I'm a little more relaxed about it having witnessed many friends canning and having done it myself. So keep in mind that there may be food spoilage issues. On the other hand, the same government agency that warns us about canning food problems can't seem to do anything about e coli on spinach on agribusiness farms, so what the hell. There are plenty of problems with foods you buy at the store--and thus any food has the potential to make you sick. You have to use your own judgment and discernment in this, as in all things.
Onwards, the only direction there is,