Furnace
A furnace is a multiblock structure that encloses a Crucible enhancing its function.
First build a forge and then place a Clay or Fireclay Crucible on top of it. A classic TFC crucible is not valid.
Then enclose the crucible on three sides (the walls) and the top (the roof) with a non-flammable solid block, such as brick block or smooth stone.
At last, completely close-off the remaining side with a chimney block. A Mud Brick Chimney block is allowed. The chimney block must not be blocked from the sky.
- Incomplete furnace
- Closed furnace - a sticky piston is used to push the last wall and complete the structure
A furnace structure allows a crucible to be heated to higher temperatures without requiring bellows and mechanization.
This allows production of glass in a crucible. It cannot be used to smelt platinum and other ores, however.
First add regular glass ingredients into the crucible input slot. The commonly used ratio is 1 x Silica Sand + 1 x Lime + 1 x Soda Ash. 2 x regular Ash can be used instead of 1 x Soda Ash. Then heat the crucible to high orange temperature. Bellows maybe be used at this point to speed the heating up, but it is not a requirement.
When the temperature reaches high orange, it is time to enclose the crucible inside a valid furnace structure. Before doing so, make sure the forge is full of fuel.
Making glass will take 8 in game hours. Smoke will rise from the chimney if the furnace structure is correct, indicating progress. When the process is complete, the smoke will stop rising and all fuel in the forge will be consumed. Add more fuel to the forge as soon as possible to keep the glass liquid if you wish to work with the glass.
The glass making period can be skipped by sleeping, and the process will continue even if you leave the area. However, having consumed all the fuel, the forge will begin to cool down and you may find the glass solidified if you take too long.
If the structure is broken before the process has finished, the smoke will stop raising and any progress is lost. The forge might need to be refueled before the furnace is reconstructed to restart the process.
Molten glass can be retrieved from the crucible into a sheet mold to create glass pane, or with a ceramic blowpipe to make bottles, or with a Metal blowpipe to craft various other glassware such as Drinking Glass.
There is a chance that a clay crucible will get ruined due to the very high temperature. When this happens, break the crucible with your hand or pickaxe to retrieve a Lump of Glass and the heat it up in a new crucible to get molten glass. The chance of a crucible getting ruined is configurable and the default setting is that it happens every time.
- In earlier versions a bellows was required in this structure which was too expensive and made it impossible to build in the stone age.