40d:Melt item

You can melt items at a smelter, using the furnace operator labour, to recover some of the metal they were made of. Decorations in a different metal are not recovered or considered; the metal recovered is the specific metal that basic item was listed as being made from. The % return is predictable and consistent for each item type, and ranges from 10%-60%, depending on the item. Higher skill levels in furnace operator speed up the process, but have no effect on the % return.

Recovered metal is measured in 1/10th's, and 1/10ths of bars of each metal are saved at the smelter where the item was melted. Fractional bars are not "shared" between smelters, nor do they exist as usable objects as is. When 10/10ths of a type of metal are accumulated at the same smelter, 1 bar of that metal is produced. If the smelter is torn down or destroyed, all fractions are lost.

Example: If two items of the same metal worth .4 bars each are melted at the same smelter, that smelter has .8 bars worth waiting in it.

If a similar item of a different metal is then melted there, that smelter would have .8 bars of the first metal and .4 bars of the second.

If a similar item of the first metal is then melted at a different smelter, that smelter will have .4 of that metal, and have no connection to the fractions in the first smelter.

If (finally!), a 3rd, similar item of the first metal is melted at the first smelter, adding another 4/10ths, and giving a total of 12/10ths of that type of metal, 1 bar of that metal is produced, and 2/10th's are waiting (plus the 4/10 of the second metal, also waiting).

So, it's recommended that you designate one smelter as your "melting" smelter (or one/metal type), to guarantee that fractions will add up effectively.

Designating items to melt

You can designate metal items for melting from any interface that allows you to view the object's description screen, such as from the Stocks page or the Look interface.

To bring up a individual object description screen when the object is:

On the ground: Type k, scroll to the object, select it from the list, and type Enter.
In a workshop: Type t, highlight the workshop, select the object from the list, and type Enter.
Held by a dwarf: Type v, highlight the dwarf, type i to show his inventory, select the object from the list, and type Enter.
Inside another object: Display the container's object description screen, navigate to the specific object you wish to see, and type Enter.
In the stocks menu: Type z, hit right-direction a few times to select "stocks" and press return. Scroll to the type of object you wish to melt, type Tab to show individual items (You have to have an exact number or this won't work. See Bookkeeper for how to get this.), scroll to the specific object, and type v to view.

To designate the item, simply type m to mark the object for melting. If the item is designated for melting and forbidden then the item will not be melted.

However, this only marks which items you want to be melted - you still have to place the job-order in a smelter...

Melting the items

Items designated to be melted will be left alone until you queue a "Melt a metal object" job at a Smelter. Melting down an object requires the Furnace Operator labour (and consumes a unit of fuel for a non-magma smelter).

The job gives the same experience to the furnace operator skill regardless of % yield of the item melted.

Yield

For every unit of material size an item has, 1/10th of a bar of that item's metal type will be recovered. These fractional bars are "stored" at the specific smelter where the item was melted; when a full bar's worth of one type of metal has been melted, one bar will be produced. Therefore, you should do all your melting at one smelter, at least for each different type of metal or alloy melted.

For instance, plate mail has a material size of 9, and melting one bronze suit will produce 0.9 bars of bronze. If you then melt another bronze suit, one bronze bar will be produced, with 0.8 bars remaining in the smelter. If, however, you melt one suit at each of two smelters, no bars will be produced; each smelter will have 0.9 bronze bars stored up.

Melting objects nets you fewer bars of metal than were required to make them, although for some objects this loss is much greater than for others. Some items are available cheap from traders, or are otherwise refuse, so melting is a distinct option. An entire suit of chain armor, including shield, consumes 7 bars to make - melted (and with high boots) it yields only 2.1.

Melting armour & weapons

Fortresses will often accumulate armour and/or weapons that they don't need, either from invaders, from caravans (with or without trading for them, ahem), or from unsuccessful, low-skilled early efforts at forging your own.

Rather than let these gather dust, some players choose to recycle them back into iron or steel (or bronze or copper, etc) bars.

Armour Item	Return
cap	.1
helm	.2
chain armour	.6*
plate armour	.9*
gauntlets	.2
leggings	.5
greaves	.6*
low boots	.1
high boots	.2
shield	.4
buckler	.2

(* Note that these are not % returns, as the items take more than 1 bar to make initially.)

Weapon	Return
large dagger, whip	.1
blowgun, scourge	.2
bow, crossbow, mace, scimitar, short sword, spear, war hammer	.3
battle axe, flail, longsword, pick, pike	.4
great axe, halberd, two-handed sword	.5
stack of # arrows, bolts	# /100, rounded up*

(* Round up to nearest 1/10th. A stack of 1-10 bolts or arrows produces .1 bars, 11-20 produces .2, 21-30 = .3, and 31+ = .4. A weaponsmith can produce a stack of 25 metal bolts, which produces 0.3 bars. You could "create" metal this way, if you could reliably collect individual metal bolts after they were shot (and unbroken).)

Due to the low return, many players opt to install weapons into weapon traps instead, especially if the weapon is of any quality.

Training metalsmith skills

It can consume many, many bars of metal to train the various metalsmithing skills up to high levels*. If you are short on metal, producing items, melting them and re-producing them may be necessary. If you want to retain as much metal as possible from this process, some items are better to produce and re-melt than others. The skill to be trained in the chart below is trained at a forge; melting items at a smelter only raises the Furnace Operator skill. When using a produce/melt loop to train up a skill for a minimum metal loss, the following items work best:

(* Upwards of 1,000 bars to train from unskilled to Legendary+5, the highest skill level.)

Item Melted	% Returned	Skill
enormous corkscrews, giant axe blades, menacing spikes	50%¹	weaponsmithing
leggings	50%	armorsmithing
goblet	60% (2/10 each)²	metal crafting
chain	50%	metal crafting
bucket	50%	blacksmithing
furniture³	33% (1 bar each)⁴	(not recommended for training)

Notes:

1) Some other weapons have a better return/weapon, but cannot be manufactured by dwarves, negating their value for training purposes.

2) Goblets are produced in threes, and have an individual item size of 2; 2/10 x 3 = 60% recovery/bar.

3) Includes cages and anvils, both of which are available from traders. Anvils will always be either iron or steel, while cages can be of copper, lead, nickel, tin, or zinc only.

4) Furniture takes 3 bars to create, and returns 1 bar for each item melted

Bugs

For reasons unknown, attempting to melt a metal Chest will fail. When attempting to do so, it will be carried to a smelter and the "Melt a metal object" task will be completed (granting Furnace Operating experience, and consuming fuel if not magma-powered), but the chest will not actually be melted - it will remain in the smelter's inventory to be returned to a stockpile, and no metal bars will be produced.^{v0.28.181.40d}