Editing v0.31:Magma piston

{{quality|Fine|08:37, 8 April 2011 (UTC)}}

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'''Magma pistons''' are used to move magma near the surface. This approach was developed as an alternative to [[screw pump#Pump stack|pump stack]]s. Magma pistons are used because they require less time and fewer precious materials to construct than pump stacks. However, magma pistons are a bit more complicated than pump stacks, so it takes more time to understand how to operate and build them.

The piston method is based on a clever [[exploit|abuse]] of [[cave-in]] [[physics]]. The basic principle involves channeling out an area around a huge stone pillar, hundreds of z-levels tall, which will become the "piston" that drives magma to the top. Rest the piston on a single support, then carve out a tank at its base which will be filled with magma pumped from the magma sea. ('''Beware:''' building the piston directly over the magma sea will '''NOT''' work!) Once the tank has been filled, drop the piston by removing its support. Liquids displaced by a cave-in will "teleport" straight up to the nearest available space; here, the nearest available space will be the catchment area you thoughtfully prepared earlier atop the piston.

:The '''magma reservoir''' is dug out near the magma sea. You can't actually drop the piston directly into the magma sea because the bottom of the magma sea is [[semi-molten rock]], and it will completely destroy any piston dropped into it. The magma reservoir is artificial, so it won't have a floor made of semi-molten rock. This will allow the piston to rest on the floor of your reservoir. The magma reservoir needs three parts: a magma inlet, a magma drain, and an access corridor. After letting magma in, and dropping the piston, you'll want to dig out the bottom of the piston so you can drop it again. To do that, you need to drain any excess magma and let your workers in through the access corridor.

:The '''support''' is what prevents your piston from dropping until you decide to pull the firing lever. The support can be located either at the bottom of the piston, as shown in the simplified diagram, or at the side of the piston (shown in the following diagram). If the support is at the bottom of the piston, then the support and the mechanism it uses must both be [[magma-safe]]. If it's at the side, then neither need to be magma-safe. Here's an example of a side-mounted support:

:Now drop the top of the piston on to the floor of the cavern. You can use a cave-in to destroy the stairs quickly, if you remove all up-stairs first.

:The '''obsidian caster''' is what allows you to rebuild your piston and get more magma. It's an application of techniques drawn from [[obsidian farming]]. The caster just needs to precisely dump water into the catchment area in order to form obsidian. A caster is composed of two parts: a water inlet, and a retracting bridge. Here's a sample design: