Operating a furnace is simple enough. You insert some charcoal and some ore, and start the fire. You then either wait for the charcoal to all burn, or open the furnace at some point to stop it, and take the resulting metal, and perhaps whatever charcoal remains. Any ore will be gone, regardless of when you stop the furnace. You can add additional charcoal while the furnace burns, but not additional ore.
A furnace can hold up to 1000 charcoal and 100 ore of one type. The additional charcoal added cannot give the furnace a total of more than 1000 charcoal to burn in a single run. Oddly enough, the 10 charcoal burned at the start of a run does not count toward this.
Quick Recipes
Smelting Pot
For best results, use 94 ore and 25 charcoal. Open between 4:42 and 4:59 for 8 metal (3 cc/metal, 11.75 ore/metal).
If you don't want to hang around, or have a bad memory, use 93 ore and 23 charcoal. This will stop automatically when it's done, but only produce 7 metal (3.29 cc/metal, 13.3 ore/metal).
| Ore | Charcoal | Time (min) | Metal | Notes |
| 93 | 23 | 4m04s | 7 | Fire and forget recipe - will automatically stop |
| 94 | 25 | 4m42s | 8 | You MUST open the pot at 4m42s for this recipe to work |
Smelting Block
The table below shows the relative values of metal and charcoal. All these formulas stop automatically.
| Ore | Charcoal | Time (min) | Metal | Cost (cc/metal) | Cost (ore/metal) |
| 93 | 22 | 12 | 7 | 3.14 | 13.3 |
| 94 | 27 | 17 | 8 | 3.37 | 11.8 |
| 95 | 35 | 25 | 9 | 3.89 | 10.6 |
| 95 | 48 | 38 | 10 | 4.80 | 9.5 |
| 96 | 80 | 70 | 11 | 7.27 | 8.7 |
Some theory
Ten charcoal burns immediately when the furnace starts, and the rest burns continuously. The furnace will display the amount of charcoal which has burned, rounded to the nearest integer, and this is the amount beyond the starting cost that will be gone if you stop the furnace. The rate at which charcoal burns depends on the furnace:
Smelting Pot: 1 charcoal per 20 seconds
Smelting Block: 1 charcoal per minute
Oscillation Kiln: 1 charcoal per 10 minutes
Pigback Kiln: 1 charcoal per 12 minutes
To determine how much metal will be produced, each furnace has "ticks". The number of ticks that a furnace will have had by a given time is a function of how long the furnace has been operating. Ticks grow further apart the longer a furnace has been running, so metal production is a matter of diminished returns. Quizzical claims that the formulas are:
Smelting Pot: 37.5t, with t in seconds
Smelting Block: 12t/(t+10), with t in minutes
Pigback Kiln: 24t/(t+48), with t in hours
The game takes the amount of time the furnace has been running, rounds it to the nearest second (or truncates or something like that; it's not possible to tell the difference), plugs it into the formula above, and then rounds that to the nearest integer.
To determine how much metal will have been produced, take the number of ticks times the amount of ore, divide by 100, and round that to the nearest integer. Note that this procedure involves rounding at three separate places. This often gives results different from if everything were continuous, with rounding only at the end.
Smelting pots lose some metal at 5 minutes, so if you operate a smelting pot, you'll want to stop the furnace before then. Smelting pots do not get any additional ticks beyond 5 minutes.
The above method is equivalent to having a table of known tick times, and getting the number of ticks by taking the largest number of ticks which requires less than the amount of time which has passed. With this interpretation, we can write down the tick times:
Smelting pot tick times come at:
| Tick | Time |
| 1 | 19s |
| 2 | 57s |
| 3 | 1m34s |
| 4 | 2m12s |
| 5 | 2m49s |
| 6 | 3m27s |
| 7 | 4m04s |
| 8 | 4m42s |
Smelting block tick times come at:
| Tick | Time |
| 1 | 27s |
| 2 | 1m26s |
| 3 | 2m38s |
| 4 | 4m08s |
| 5 | 6m |
| 6 | 8m28s |
| 7 | 11m50s |
| 8 | 16m40s |
| 9 | 24m18s |
| 10 | 38m |
| 11 | 1h10m |
| 12 | 3h50m |
Pigback kiln tick times come at:
| Tick | Time |
| 1 | 1h1m17s |
| 2 | 3h12m |
| 3 | 5h34m54s |
| 4 | 8h11m43s |
| 5 | 11h4m37s |
| 6 | 14h16m13s |
| 7 | 17h49m43s |
| 8 | 21h49m6s |
| 9 | 1d2h19m22s |
| 10 | 1d7h26m54s |
| 11 | 1d13h20m |
| 12 | 1d20h9m36s |
| 13 | 2d4h10m27s |
| 14 | 2d13h42m52s |
| 15 | 3d1h15m48s |
| 16 | 3d15h31m46s |
| 17 | 4d9h36m |
| 18 | 5d9h13m51s |
| 19 | 6d17h27m17s |
I've directly observed all smelting block tick times, and the smelting pot tick times were well-known by the end of beta. I haven't directly observed all pigback kiln tick times, but I was able to predict the 16th one to the exact second before observing it, and then observe that the prediction was exactly right. With that sharp of a prediction, I'm satisfied that the formula is right.
Optimal formulas
If you need metal fast, the way to do it is to put 94 ore into a smelting pot along with at least 25 charcoal, fire it, and stop the furnace somewhere between 4:42 and 4:59 (ideally by 4:49, so you get an extra charcoal back). This will get you 8 metal in under 5 minutes. The other furnaces take much longer, so let's otherwise assume that running time is not a factor.
Let's start by assuming that you want a "fire and forget" furnace run, where you insert the ore and charcoal, fire it, leave, and come back sometime after it runs out of charcoal. This cannot be done with an eight tick smelting pot run, as 24 charcoal won't get you to the eighth tick, while 25 will hit the five minute mark. For seven or fewer ticks, it takes less charcoal to use a smelting block than a smelting pot, so I wouldn't bother with smelting pots for fire and forget runs.
The optimal formula then depends on the relative value of charcoal and ore. I've listed all the formulas that can be optimal, and at each line where some amount of charcoal is equal to some amount of ore, the formulas immediately above and below are equally efficient. Each formula is labeled with "block" for a smelting block or "pigback" for a pigback kiln. There is very little data on oscillation kilns out there, so for now, I'll assume that they don't exist.
22 charcoal, 93 ore => 7 metal (12 min/block)
86 ore = 13 charcoal
27 charcoal, 94 ore => 8 metal (17 min/block)
86 ore = 37 charcoal
35 charcoal, 95 ore => 9 metal (25 min/block)
95 ore = 82 charcoal
48 charcoal, 95 ore => 10 metal (38 min/block)
5 ore = 16 charcoal
80 charcoal, 96 ore => 11 metal (70 min/block)
469 ore = 3648 charcoal
448 charcoal, 97 ore => 16 metal (3 days, 15 hours, 36 min/pigback)
81 ore = 992 charcoal
538 charcoal, 98 ore => 17 metal (4 days, 9 hours, 36 min/pigback)
98 ore = 1485 charcoal
657 charcoal, 98 ore => 18 metal (5 days, 9 hours, 24 min/pigback)
98 ore = 2241 charcoal
818 charcoal, 98 ore => 19 metal (6 days, 17 hours, 36 min/pigback)
3 ore = 94 charcoal
48 charcoal, 5 ore => 1 metal (38 min/block)
1 ore = 223 charcoal
271 charcoal, 4 ore => 1 metal (2 days, 4 hours, 12 min/pigback)
1 ore = 267 charcoal
538 charcoal, 3 ore => 1 metal (4 days, 9 hours, 36 min/pigback)
Note that unless you're dealing with ore valuable enough that one ore is worth at least about 8 charcoal, pigback kilns have no point. It remains to be seen whether there will be such valuable ores. The pigback kiln is this telling's equivalent to the old precious furnace (construction costs are nearly identical), which was useful only for red sand and metal blue.
It was above noted that for smelting pots to be efficient, you have to watch the pot to prevent it from boiling, by opening it between 4:42 and 4:59. If you open the pot between 4:42 and 4:49, it costs 24 charcoal for 8 metal, compared to 27 charcoal to get 8 metal from a smelting block. This is more efficient than any of the above smelting block formulas if 43 ore is worth less than 32 charcoal.
Technically, some of the formulas can save 1 charcoal by opening the furnace after the last tick, but before the last charcoal completely burns. This is probably a waste of time to stand and watch the furnace.
Some limitations
I haven't tried running a pigback kiln with less than 100 ore. I've assumed above that using less ore there works the same as using less ore in other kilns. The 16th tick of a pigback kiln is the only one that I directly observed to the second, though I have observed several others to within a few minutes. My formula fits all known data, and was able to predict the time of the 16th tick before it was observed, which is good evidence in favor of the formula. The rest of the listed tick times come from the formula.
I don't have an oscillation kiln, so I haven't had a chance to experiment with it. As of this writing, I'm not aware of any significant oscillation kiln data. There are a few scattered data points on the wiki, but not nearly precise enough to come up with a formula with any serious hope of being right. If someone could find a few tick times of an oscillation kiln to within a few minutes, including one at least a day or so into the run, I could likely come up with a formula for it.
Building information
Pigback Kiln
Materials: 60 firebricks, 40 leather, 24 copper wire, 40 slate, 100 small quartz, 4 copper straps
This is a very slow furnace, which is ore-efficient, but uses a lot of charcoal. It is analogous to the old Precious Furnace.
Smelting Pot
Materials: 1 crucible, 50 firebricks
This is a fast furnace which is charcoal-efficient, and good for making metal from cheap ores.
The following is from Beta2, but seems to be unchanged:
Prel's Raw Data
| Time (mm:ss) | Ore Used | Charcoal | |||||||||||||||||||
| 100 | 94 | 90 | 85 | 80 | 75 | 70 | 65 | 60 | 55 | 50 | 45 | 40 | 35 | 30 | 25 | 20 | 15 | 10 | 5 | ||
| 0:19 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | ||||||||||
| 0:57 | 2 | 2 | 2 | 2 | 2 | 2 | 1 | 1 | 1 | 1 | 1 | ||||||||||
| 1:34 | 3 | 3 | 3 | 3 | 2 | 2 | 2 | 2 | 2 | 2 | 1 | ||||||||||
| 2:12 | 4 | 4 | 4 | 3 | 3 | 3 | 3 | 3 | 2 | 2 | 2 | ||||||||||
| 2:49 | 5 | 5 | 5 | 4 | 4 | 4 | 4 | 3 | 3 | 3 | 2 | ||||||||||
| 3:27 | 6 | 6 | 5 | 5 | 5 | 5 | 4 | 4 | 4 | 3 | 3 | ||||||||||
| 4:04 | 7 | 7 | 6 | 6 | 6 | 5 | 5 | 5 | 4 | 4 | 3 | ||||||||||
| 4:42 | 8 | 8 | 7 | 7 | 6 | 6 | 6 | 5 | 5 | 4 | 4 | 24 | |||||||||
| 5:00 | 6 | Depends | |||||||||||||||||||
Smelting Block
Materials: 2 crucibles, 150 firebricks, 125 limestone, 30 flint
This is an intermediate furnace, more charcoal efficient than a pigback kiln, but more ore-efficient than a smelting pot.
| Time (hh:mm:ss) | Ore Used | Charcoal | |||||||||||||||||||
| 100 | 96 | 95 | 94 | 80 | 75 | 70 | 65 | 60 | 55 | 50 | 45 | 40 | 35 | 30 | 25 | 20 | 15 | 10 | 5 | ||
| 0:01:00 | 1 | 1 | 1 | 1 | 1 | 0 | 11 | ||||||||||||||
| 0:02:00 | 2 | 2 | 2 | 2 | 1 | 0 | 12 | ||||||||||||||
| 0:03:00 | 3 | 3 | 3 | 3 | 2 | 0 | 13 | ||||||||||||||
| 0:05:00 | 4 | 4 | 4 | 4 | 2 | 0 | 15 | ||||||||||||||
| 0:06:00 | 5 | 5 | 5 | 5 | 3 | 0 | 16 | ||||||||||||||
| 0:09:00 | 6 | 6 | 6 | 6 | 3 | 0 | 19 | ||||||||||||||
| 0:12:00 | 7 | 7 | 7 | 7 | 4 | 0 | 22 | ||||||||||||||
| 0:17:00 | 8 | 8 | 8 | 8 | 4 | 0 | 27 | ||||||||||||||
| 0:25:00 | 9 | 9 | 9 | 8 | 5 | 0 | 35 | ||||||||||||||
| 0:38:00 | 10 | 10 | 10 | 9 | 5 | 1 | 48 | ||||||||||||||
| 1:10:00 | 11 | 11 | 10 | 10 | 6 | 1 | 80 | ||||||||||||||
| 3:50:00 | 12 | 12 | 11 | 11 | 6 | 1 | 240 | ||||||||||||||
Oscillation Kiln
Materials: 20 cut stone, 6 crucibles, 24 leather, 4 copper sheeting, 2 iron bars, 2 sheet glass, 300 firebricks,
The optimal use of this furnace is unknown. Given a few tick times, it would probably be possible to determine the relevant formulas which would make the proper use of this furnace clear.
Actually, it seems to be a bit more effiecent than the pigback kiln. 98 ore and 452 cc will make 18 metal in about 3 days 4 hours. the pigback kill will take 97 ore and 448cc and turn it into 16 metal in 3days 15hours -Mudkest:
Operation
The oscillation kiln can also be started with 1000 charcoal and 100 of any single ore. Upon firing 10 charcoal are consumed immediately then 1 after 5m8s and then 1 every 10m17.5s.
| Time (dd:hh:mm:ss) | Ore Used | Charcoal(1) | |||||||||||||||||||
| 100 | 94 | 90 | 85 | 80 | 75 | 70 | 65 | 60 | 55 | 50 | 45 | 40 | 35 | 30 | 25 | 20 | 15 | 10 | 5 | ||
| 00:00:05:08 | 0 | 0 | 0 | 0 | 0 | 1 | |||||||||||||||
| 00:00:15:00 | 0 | 0 | 0 | 0 | 0 | 2 | |||||||||||||||
| 00:01:29:00 | 1 | 1 | 0 | 0 | 0 | 9 | |||||||||||||||
| 00:03:36:00 | 2 | 1 | 1 | 1 | 0 | 21 | |||||||||||||||
| 00:09:15:00 | 4 | 54 | |||||||||||||||||||
| 00:14:30:00 | 7 | 85 | |||||||||||||||||||
| 00:17:30:00 | 7 | 102 | |||||||||||||||||||
| 00:18:20:00 | 8 | 107 | |||||||||||||||||||
| 00:20:35:00 | 8 | 120 | |||||||||||||||||||
| 00:23:05:01 | 9 | 135 | |||||||||||||||||||
| 01:01:01:43 | 9 | 146 | |||||||||||||||||||
| 01:10:17:09 | 12 | 200 | |||||||||||||||||||
| 01:18:51:26 | 13 | 250 | |||||||||||||||||||
| 01:22:17:30 | 14 | 270 | |||||||||||||||||||
| 02:03:05:09 | 14 | 298 | |||||||||||||||||||
| 02:06:46:48 | 15 | 320 | |||||||||||||||||||
| 02:09:18:54 | 16 | 334 | |||||||||||||||||||
| 03:03:49:54 | 18 | 442 | |||||||||||||||||||
| 03:13:07:54 | 18 | 497 | |||||||||||||||||||
| 03:17:48:21 | 19 | 524 | |||||||||||||||||||
| 04:10:42:28 | 20 | 622 | |||||||||||||||||||
| 04:21:43:49 | 20 | 687 | |||||||||||||||||||
| 05:07:42:04 | 19 | 746 | |||||||||||||||||||
| 05:09:15:43 | 20 | 754 | |||||||||||||||||||
| 06:11:36:46 | 19 | 908 | |||||||||||||||||||
| 07:01:42:51 | 20 | 990 | |||||||||||||||||||
- (1) add 10 charcoal from firing the kiln
| Name | Image | Notes |
| Aggregate |  | I started both at the same time |
 | Oscillation Kiln has 2 more metal | |
 | Ended with 16 Aluminum |
Reactory
The reactory produces alloys by smelting metal together. It is fueled by 100 oil
See the alloys guide.
Fleet Furnace
Turns red sand into quicksilver. Place 10 red sand and 20 cc in the furnace. 24 Teppy-hours later, you get 1 quicksilver.
Note: You can leave quicksilver in the furnace, you needn't remove it every time. But you cannot remove quicksilver if the furnace is firing.
Vitiation Kiln
Can hold up to 100 ore, and 1000 petroleum. Burns 10 petroleum on start up, then 15 petroleum per hour. 100 petroleum will give 6 hour running time.
At time 0 uses 10 petroleum, at 2 minutes uses 1 petroleum, every additional 4 minutes uses 1 additional petroleum.
Tick times (from Quizzical) are as follows:
| Tick Number | Time | Petrol Required | Metal/Petrol |
| 1 | 2:19:22 | 46 | 0.0217 |
| 2 | 7:26:54 | 123 | 0.0163 |
| 3 | 13:20:00 | 211 | 0.0142 |
| 4 | 20:09:36 | 313 | 0.0128 |
| 5 | 1:4:10:27 | 434 | 0.0115 |
| 6 | 1:13:42:52 | 577 | 0.0104 |
| 7 | 2:1:15:48 | 750 | 0.0093 |
| 8 | 2:15:31:46 | 964 | 0.0083 |
| 9 | 3:9:36:00 | 1235 | 0.0073 |
The figures for 9 are theoretical, not achievable, due to the cap on petrol put into the furnace.
The highest possible yield from this furnace is 8 metal, and requires 964 petrol, and 2 days, 15 hours 31 minutes and 46 seconds to create.
These are my experiments /MrStoned
| Ore | Pet | Metal | Ore/Metal | Petrol/Metal | RunTime |
| 100 | 577 | 6 | 1d13h48m | ||
| 98 | 577 | 6 | |||
| 96 | 577 | 6 | |||
| 95 | 577 | 6 | |||
| 94 | 577 | 6 | |||
| 93 | 577 | 6 | |||
| 92 | 577 | 6 | 15.3 (Optimum) | 96.2 | |
| 91 | 577 | 5 | |||
| 90 | 577 | 5 | |||
| 89 | 577 | 5 | |||
| 88 | 577 | 5 |
Probably optimum values for best performance
| Ore | Pet | Metal | Ore/Metal | Petrol/Metal | RunTime |
| 92 | 577 | 6 | 15.3 (Optimum) | 96.2 | 1d13h48m |
| 90 | 434 | 5 | 18 | 86,8 | 1d4h10m |
| 88? (To be verified | 313 | 4 | 22? | 78,25 | 20h09m |
