Obsidian farming is very useful, especially earlier in the game, when massive caverns have not been found yet. Obsidian farming is accomplished by pouring lava in a trench (must be still) and then pour water so that it flows over the top, creating obsidian. This is the favored way to obtain obsidian, because mining or finding obsidian is very risky and dangerous. Obsidian is always near lava (unless all of the lava has been converted to obsidian) (since lava is needed to create it), so you must either block off the lava or swim against the current of the water. With farming, all you do is place the lava and pour the water yourself, making it less dangerous. The only dangerous part is getting the lava with a bucket. You need source blocks for this; as "flow" lava will produce only stone or cobblestone. The lava flows found in many caves usually have a single source block which you can scoop with the bucket. There are also lava "lakes" which consist entirely of source blocks. They are common at and below level 10, but can occasionally be found on the surface, as well.
The most plentiful source of lava would be the Nether... but if you can build portals, you can use those to farm obsidian — and unlike lava drenching, portal farming is renewable.
 Exploration tips
- Bring plenty of torches to light up the cave, weapons to defend yourself, pickaxe and shovel to collect any ores you find on the way down to the lava layers. An Axe is optional, but can be useful when you are exploring an Abandoned Mineshaft.
- Armor is useful too.
- If you see a light in an area you have not previously explored, it is probably caused by lava.
- If you see red particles dropping from the bottom of blocks, there is lava above those blocks. It's probably best to get above that lava, if you're hoping to collect it.
If you go to the Nether to get lava or for portal farming, there are several rules/tips/hints:
- Read the Tutorial on surviving the Nether.
- If you're gathering lava:
- Those flows and falls you see around you are mostly coming down from the very top of the Nether, so finding the source block can be difficult. Look for lava lakes or the lava sea. (Generally downward. Be sure you can get back up!)
- Bring many buckets at a time, because depending on how close your portal is to the "lava ocean", it might take a while to get there. Also, make sure you have room in your inventory to fill them.
- Bring plenty of pickaxes, at least a couple of iron ones.
- Don't mess with Zombie Pigmen, but have a good sword just in case. (Magma cubes, Blazes and Wither Skeletons may show up; those you can kill freely, however be careful of the Wither Skeletons.)
- Bring lots of cobblestone for Ghast shelters, and a good bow to shoot them down.
- Never dig straight down. Be very careful around edges.
- Bring some Flint and Steel, in case a Ghast deactivates your portal.
 Lava drenching methods
The simplest way is to find a lava pool and dump a water bucket next to the edge. This will convert the nearby lava into obsidian. Mine out one block at the edge, then pick up your water source and put it in the hole. Now you can work your way out from the water, and any lava uncovered will be automatically converted (before it burns your mined obsidian, even).
If you already have the lava and want to convert it, find an open area (you'll need at least a 1×7 trench), and try one of these methods:
 Scaffolding and Casting
Structures (most often a Nether Portal) can be constructed out of Obsidian without the use of a diamond pickaxe, by creating a mold and placing the lava source within it, then running water over the lava. This will form the obsidian in place, but without diamonds it is quite hard to get rid of. Casting may be better than drench mining when you have a lot of buckets, and the still lava is nearby.
A much faster form of obsidian creation for large structures can be made by building "scaffolding" to create a frame two away from the desired location of the Obsidian and using this to create an artificial waterfall a square away from where Obsidian is wanted. It is then possible to "float" inside of the waterfall and create large amounts of obsidian by placing buckets of lava next to it. This has the advantages of not needing to be built up and have the water moved with every new row, and allows the maximum of 36 buckets of lava to be converted at once. Care should be taken to remain clear of the row where obsidian is being created, however, as the solid block created can hurl the player through the air and cause a large amount of fall damage.
|Obsidian Scaffolding Guide Video (view on YouTube)|
 Basic Farm
This is basically just a trench dug into the ground with walls on either side; nothing special. It gets the job done without all the luxuries. It is simply made by digging (at least) a 1x7 trench in the ground and building short walls on either side. You then pour lava in the trench, making sure that each space gets its own source block. Each end has a step; this is required for the water to flow onto the lava. Once the trench has been filled with lava source blocks (when the lava is completely still), you can then pour the water onto the "step" and it will flow over the lava, transforming it into obsidian. "Pick up" the water spring with the bucket and begin to mine the obsidian. Note that you need a diamond pickaxe to mine it successfully.
 Advanced Farm
This type of farm is a little more sophisticated than a hole in the ground. It is for permanent buildings or to make your farm look better. What you will need to do to build it is start to make a basic farm. Make the walls one block higher and make a roof (this is optional, and so is glass; it's only for aesthetic purposes). Next, make a small structure at one end of the trench. This is helpful for storing buckets and other supplies. At the other end, make a way to get up to pour water. If you added a roof, you will have to be extra careful when pouring the lava because there is only one way out, which is why it is suggested that you block the flow with dirt so that it does not keep you from pouring the other buckets. Pour the bucket of water in and you're good to go.
 Redstone-To-Obsidian Glitch ("Infiniobsidian")
On the 16th of March 2011, a new way was discovered to farm obsidian involving redstone as the only irretrievable source (rather than lava). The process involves having a row of running water with a line of redstone next to it and pouring the lava onto the redstone, in-turn, replacing it with obsidian. It is, however, important to note that only unpowered redstone will become obsidian; powered redstone transforms into cobblestone. Better still, it is renewable, as you can trade redstone from villagers, and also you can get them from witches. Lava and water and buckets are not consumed if used correctly!
|“||Indeed! I foresee a bunch of patches if competitive play ever takes off, though. Infiniobsidian is probably OP.||„|
|~ Notch on reddit.com|
|Obsidian generator building method Video (view on YouTube)|
|Redstone-to-Obsidian with pistons Video (view on YouTube)|
|Obsidian house with Redstone-to-Obsidian Video (view on YouTube)|
|Variable-size design Video (view on YouTube)|
The scaffolding method can also be combined with the redstone-to-lava ("Infiniobsidian") bug to great effect, this is currently the fastest method for creating large obsidian structures.
|Infinobsidian using Obsidian Scaffolding Video (view on YouTube)|
 Portal Farming
You can also farm Obsidian with Nether portals, provided you already have enough to make two portals (at least 20 blocks, but 28 is a bit easier). Unlike drenching lava, this method is renewable. Note that this is complicated by the point that simply making two portals in the Overworld within some 1024 blocks of each other, will likely link to the same portal in the Nether. However, you can proceed as follows:
Create a Nether portal in the Overworld, travel to the Nether. Move at least 16 blocks within the Nether (but not much more), and build a second return portal, then use it, returning to the Overworld. This will create a second portal in the Overworld, some 128-plus blocks from the first. You can then mine the new portal and return to the first one. Returning to the Nether, you will find both portals still functional, and using the second will again create a new portal in the Overworld. This can be repeated as many times as you like.
A more brutal farming method only requires a single portal pair; travel to the nether side and de-activate the portal (break the frame/Ghast's fireball). Stash all your items in a chest (or better, an Ender Chest) and kill yourself. You'll re-spawn in the Overworld. Re-enter your portal and a new frame of 14 obsidian will be created next to your broken one, allowing you to mine the broken one. Note that this way, you are mining the obsidian (slowly) in the dangerous Nether rather than the Overworld.
In SMP, two players can cooperate on farming Obsidian with portals, making the process much faster. One player makes a portal in the Overworld and uses it to enter the nether. This creates a portal in the nether, their way back. The other player, still in the Overworld, breaks one block in their side of the gate, destroying the portal. (In fact, at this point they can go ahead and mine the rest of the gate.) The player still in the nether then reenters their portal. Besides returning them to the Overworld, this produces a new gate near the old destroyed one. Repeat until you have enough obsidian.
For the most advanced players, using an end portal creates a 5X5 obsidian spawn platform, which regenerates every time the portal is used; However, getting back requires either having killed the Enderdragon, or killing yourself. This method has higher dividends than Nether Portal farming, and is riskier if the platform is in the air with nothing below.
|Basic Obsidian Farm Video (view on YouTube)|
 Automatic Obsidian Generators
The biggest problem with obsidian mining is the mining part - even if you use the best (no mod) pickaxe, it takes 2.5 seconds to mine a single block. Various methods have been used (and patched) to break obsidian blocks automatically, especially with the appearance of the Wither boss which is capable of breaking obsidian blocks with his attacks.
One of the first designs used the Wither to break portions of the 5x5 obsidian spawn platform in the end, and regenerating it with a sand generator that pushed sand through the end portal situated in the overworld. This method was patched however when the Wither was made to shoot blue skulls that were capable of breaking any block (before that the only way for it to break blocks was through getting damaged and breaking any block in a 3x3x4 area around it, making caging it quite simple with cobblestone generators). The following video is an explanation of how this method works. WARNING: this method works only in minecraft 12w36a and several earlier versions.
|Original Fully Automatic Obsidian Farm Video (view on YouTube)|
Recently a new method of caging the wither has been discovered that once more made an automatic obsidian farm possible. Once again it uses the wither to break portions of the end platform, but the process has been streamlined to deliver 9 obsidian per second consistently; meaning that it is possible to fill up a double-chest in 6.5 minutes. This works from minecraft version 1.5 to 13w38c. WARNING: due to differences between single player and multi-player, this method is only 100% safe in multiplayer worlds; if set up in a single player world, the Wither boss has around a 50% chance of escaping within 10 hours.
|New 9 obsidian per second Fully Automatic Obsidian Farm Video (view on YouTube)|
 Pillar farming
The End has multiple unsightly solid obsidian pillars that may be dismantled at will, giving a lot of obsidian (though you will have a random bedrock floating where the end crystal was). Since these pillars are big consider grabbing yourself a haste 2 beacon so each block takes about a second to break. You can also recycle the 5x5 spawn area, made of obsidian.
Since the end is made of end stone mine out all that as well, since it's considerably blast resistant as well. Then you can build your base in a huge blank world! (Except of course for the floating bedrocks, exit portal and the forever-regenerating obsidian platform)