Obsidian forms when water flows over a lava source. A diamond or netherite pickaxe is required to mine the resulting blocks, but you can cast a portal frame in place with lava, water and a temporary mold if you do not have either pickaxe. A Nether portal frame can be 4×5 to 23×23 blocks; leaving its four corners empty reduces the smallest conventional frame to 10 obsidian. Build the frame, clear its 2×3 opening, and ignite it with flint and steel, a fire charge or another suitable fire source.
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What obsidian does in Minecraft
Obsidian is the durable volcanic-looking block used for Nether portal frames and several advanced structures. In ordinary survival play, the important distinction is between creating obsidian and collecting it: water must contact a lava source to create the block, and breaking a placed obsidian block for pickup requires a diamond or netherite pickaxe.
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1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsThat tool requirement does not prevent an early Nether trip. A player who has iron, a bucket, lava and water can cast the blocks directly where the frame will stand. The cast-in-place method takes more setup and careful fluid handling, but it avoids waiting for diamonds.
Choose your obsidian route
| Route | What you need | Best use | Main trade-off |
|---|---|---|---|
| Mine converted lava | Water, lava source blocks, and a diamond or netherite pickaxe | Collecting blocks for a portal or later projects | Requires the appropriate pickaxe before any blocks can be harvested |
| Cast the frame in place | Lava source blocks, water, at least one bucket, and a temporary dirt or cobblestone mold | Building a first portal before obtaining diamonds | Slower and more hazardous because lava must be placed accurately |
| Salvage a ruined portal | Access to a generated ruined portal and a suitable pickaxe for blocks you want to take | Supplementing your supply or finding a convenient starting location | Generation, condition and location are situational |
| Nether or End structures | Access to the relevant structure and the tools needed to recover blocks | Later-game expansion or replacing a lost supply | These are exploration methods, not dependable first-portal plans |
| Advanced renewable methods | A developed world and a design suited to the current game edition | Large long-term projects | More complex than mining or casting and sensitive to version details |
For a first survival portal, use a nearby, controllable lava source if you can. A ruined portal is useful when it happens to be accessible, while advanced Nether and End techniques are better treated as optional projects after you understand the basic method.
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Materials and a safe work area
Prepare the work site before touching lava. A flat area makes the frame easier to count, and a temporary mold gives flowing fluids something to stop against.
- A bucket and a source of water. Carrying a second bucket makes repeated casting faster, but one bucket is enough if you refill it between placements.
- Access to lava source blocks, preferably in a pool or another location where you can stand safely.
- Building blocks such as dirt or cobblestone for the mold and for barriers around the work area.
- Flint and steel for the simplest ignition method, or a fire charge or another suitable fire source.
- A diamond or netherite pickaxe if you intend to mine and carry obsidian rather than cast the frame where it belongs.
Keep ordinary building blocks and water within reach, but do not place water casually next to an active lava pool. Work from a protected edge, block off routes where lava could spread, and leave yourself a clear escape path.
Method 1: Make obsidian and mine it
1. Find a controllable lava source
Locate a lava pool or another source block you can approach without being surrounded. The conversion step depends on source lava, not merely a thin stream flowing away from it. If a pool is in a cramped cave, first create a small standing platform and block dangerous side channels.
2. Place water over the lava
Use the bucket to let water flow across the lava source. Where the water contacts a source, the lava becomes obsidian. Move the water deliberately so you convert only the blocks you can later reach and mine safely.
3. Mine the converted blocks
Equip a diamond or netherite pickaxe and break the obsidian. The tool requirement applies to collecting the block: using a weaker pickaxe does not give you portable obsidian for your frame. Mine from a stable ledge, because unconverted lava can remain beneath or beside the block you are breaking.
4. Store and count your supply
Set aside at least 10 blocks for the cornerless minimum frame, or 14 for a complete 4×5 outline. Bring extra blocks if you want a wider opening, a complete-corner design, or replacements for mistakes. Once the blocks are in your inventory, you can build the frame at a safer location rather than beside the original lava pool.
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Method 2: Cast a portal without a diamond pickaxe
Casting turns the frame location into the mold. You place lava source blocks one at a time where obsidian should be, then use water to convert each source. Because the blocks are created in their final positions, you never need to mine them.
1. Mark the frame footprint
Choose a level, nonflammable location and outline the rectangle with temporary dirt or cobblestone. The smallest conventional frame is four blocks wide and five blocks tall, measured across the outside of the rectangle. Leave the four corners empty if you want the 10-block version.
2. Build a temporary mold
Extend the temporary blocks around the outline so lava cannot run away from the intended positions. Support the sides and top, and create a safe place from which to place each lava source. The mold is scaffolding, not part of the finished portal, so use inexpensive blocks you can remove later.
3. Cast each bottom and side position
Place a lava source in one marked position, then flow water over that source until it becomes obsidian. Refill the bucket and repeat for the next position. Work methodically along the bottom and up both sides, checking that each converted block is actually part of the frame before moving higher.
4. Cast the top and remove the mold
Finish the upper row while the temporary supports still hold the fluid. Once every required frame position is obsidian, collect the water and dismantle the dirt or cobblestone mold. Inspect the opening for stray blocks or remaining lava before attempting ignition.
5. Keep the process safe
- Never stand where a newly placed source can flow onto your only exit.
- Use barriers to separate the casting area from nearby caves, wooden structures and drops.
- If water appears to run past a position instead of converting it, stop and rebuild the mold rather than chasing the flow.
- Leave the temporary supports in place until the final upper blocks have solidified.
Portal dimensions and obsidian counts
The game accepts rectangular vertical frames from 4×5 through 23×23 blocks. The dimensions include the outside edge of the frame, not just the glowing opening. The interior is the open rectangle inside that edge.
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| Outside frame | Interior opening | Complete outline | With four corners omitted |
|---|---|---|---|
| 4×5 | 2×3 | 14 obsidian | 10 obsidian |
| 5×6 | 3×4 | 18 obsidian | 14 obsidian |
| 10×7 | 8×5 | 30 obsidian | 26 obsidian |
| 23×23 | 21×21 | 88 obsidian | 84 obsidian |
For a rectangular frame with outside width W and height H, a complete outline uses 2W + 2H − 4 blocks. Removing the four corners subtracts four blocks. That arithmetic explains why a 4×5 frame needs 14 blocks when complete but only 10 when its corners are omitted.
Why start with the minimum?
A 4×5 frame gives the smallest conventional opening and the lowest material cost. It is easier to cast, easier to shelter and less likely to be miscounted. Build larger frames when you have a practical reason, such as a planned base entrance or a portal room; the game’s upper limit is 23×23.
Corner blocks are optional
The four corners do not have to be obsidian for the rectangular frame to work. Placing temporary blocks at the corners while building can help you keep the shape square, then you can remove them or leave the corners open. If you prefer a solid-looking rectangle, budget the complete-outline amount instead.
How to activate the finished frame
1. Clear the interior
Remove every block from the opening. On the minimum frame, that opening is 2×3. Check the floor, ceiling and both sides so no temporary mold block remains inside the rectangle.
2. Ignite the frame
Use flint and steel on the empty interior or along the inside edge. A fire charge or another suitable fire source can also start the portal. Once the frame activates, the interior fills with the portal effect and becomes usable.
3. Test from a safe approach
Keep the surrounding floor clear and make sure you can step away from the portal. If you are testing a freshly cast frame, remove leftover water and confirm that no lava is hidden behind the temporary supports.
Rank #4
Troubleshooting a portal that will not work
The lava did not become obsidian
Check that water actually contacted a lava source block. A flowing tongue of lava can behave differently from the source that feeds it. Stop the flow, expose the intended position and try again with the mold supporting the water.
You cannot pick up the obsidian
Mining and casting are separate approaches. If you are trying to collect a block, use a diamond or netherite pickaxe. Without one, leave the converted block in place and continue casting the frame around it.
The frame is the wrong size
Measure the outside edge. A valid rectangular frame is at least 4×5 and no larger than 23×23. Count the two vertical sides and the two horizontal sides separately, and remember that omitted corners reduce the total but do not change the outside dimensions.
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The portal will not ignite
Verify that the frame is a vertical rectangle, the interior is empty and the frame falls within the accepted size range. Try flint and steel on the opening again after removing any misplaced blocks. A fire charge or another suitable fire source is an alternative if your first ignition method is unavailable.
Lava escaped while casting
Do not rush to retrieve a source block. Block the escape route with cobblestone or another safe building material, collect or neutralize the water when it is safe, and rebuild the mold before placing another source. Casting is most reliable when every position has a physical stop on all sides where fluid could travel.
The destination is unexpected
Portal linking and edge cases can depend on the current Java or Bedrock release. Core construction rules are stable, but advice about unusual linking layouts should be checked against the exact edition and version you are playing before you build a large network.
Other ways to obtain obsidian
Ruined portals
Ruined portals can provide ready-made obsidian in the Overworld or Nether. They are useful salvage sites when one generates near your base or route. Inspect the structure before dismantling it: preserve any blocks you want for a complete frame, and treat nearby lava and uneven terrain as hazards.
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Nether and End structures
Certain structures in the Nether and End contain obsidian or use it as part of their construction. These sources become more practical once you can travel safely and bring the appropriate mining tool. They are exploration options rather than substitutes for a carefully planned first portal.
Advanced renewable sources
Advanced portal-based and End-based methods can make obsidian renewable in established worlds. Their designs are more technical, consume time and may depend on edition-specific behavior. Use them when your project needs a sustained supply, not merely the 10 or 14 blocks required for an initial 4×5 frame.
Planning a reliable first portal
- Secure the site. Pick a flat location with room for a shelter, a clear exit and a protected approach to the frame.
- Choose your route. Mine converted lava if you already have the required pickaxe; otherwise prepare a mold and cast the frame in place.
- Budget the blocks. Reserve 10 for a cornerless 4×5 frame or 14 for a complete outline. Add more only when the planned dimensions require it.
- Build before lighting. Finish the rectangle, remove the mold and clear the interior so you are not handling lava while trying to ignite the portal.
- Keep a fallback. Store spare building blocks, water and an ignition method nearby. A small shelter makes recovery easier if the first attempt leaves fire or lava in the wrong place.
This order separates the dangerous fluid work from the final activation step. It also lets you change from a mined-block plan to a cast-in-place plan without redesigning the portal itself.
Edition and version considerations
The frame dimensions, optional corners, obsidian tool requirement and basic ignition methods described here are the survival fundamentals. Java and Bedrock players should still confirm behavior against the current release when planning unusual portal-linking systems, large networks or advanced renewable designs. A tutorial written for an older release may describe edge cases that do not match your world.
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Quick checklist
- Water and at least one bucket are ready.
- Lava source blocks are accessible from a safe position.
- You have a diamond or netherite pickaxe for mining, or inexpensive blocks for a casting mold.
- The planned frame is between 4×5 and 23×23 blocks.
- You have counted 10 blocks for the smallest cornerless frame or 14 for a complete 4×5 outline.
- The 2×3 minimum opening, or the larger planned opening, is completely clear.
- Flint and steel, a fire charge or another suitable fire source is available.
- The site has barriers, an escape path and no exposed route for lava to reach your base.
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