Many damaging corpses do not cause their usual damage if tinned; normally, Z and M are sickening to eat, but they may become edible when tinned. Poisonous and acidic corpses are also rendered harmless. However, corpses which turn you to stone, stun you or cause you to hallucinate will still have the same effect when tinned. Additionally, tins of corpses will provide the same intrinsic as a corpse alone. This makes them quite useful when working with giants and dragons, and for keeping tengu corpses to eat once you have a ring of teleport control to avoid getting uncontrolled teleportitis.
Tins made from a tinning kit always have the same BUC status as the tinning kit, and are either homemade or rotten; its status as homemade or rotten is determined when the tin is eaten. Blessed tins are never rotten and can be opened in one turn. Uncursed tins are occasionally rotten and cursed tins always are. Homemade tins of foo only have 50 nutrition, making it possible to consume several giants or dragons without becoming satiated. Rotten tins provide negative 50 nutrition.
Tinning kits only have a limited number of charges, and may need to be recharged after much use. See Charging#Tinning kit for more details.
There are many situations in which tinning a corpse is a good idea.
- If you are satiated, tin monsters which may grant intrinsics you don't have yet to save them for later. Similarly, tinning giants is useful because they boost strength.
- You may also want to tin intrinsic-granting corpses when you already have the intrinsic in case you lose it. This is particularly useful with dragons and floating eyes which are guaranteed to grant their respective intrinsics.
- As discussed above, poisonous and sickening corpses become safe to eat when tinned.
- Tin tengu and eat them once you have a ring of teleport control
- Tin multiple tengu, and multiple telportation-granting creatures (nymphs, leprechauns, etc.). Eat the latter until you get teleportation, then eat the former until you get teleportation control.
- Tin an invisible stalker and eat it once you have some means of becoming invisible, even if temporarily. You will gain the invisibility and see invisible intrinsics permanently from one meal.
- A blessed tin of nurse meat will restore you to full health in two turns. But be warned - for humans, this is cannibalism.
- Tinning a troll is a good way to keep it from reviving.
- A blessed tin of acid blob always opens in one turn and can save you from stoning.
- Tinning can be performed while riding so you don't need to dismount to eat corpses. This can be important if you are not a knight and your steed is difficult to tame (e.g. Ki-rin).
Tinning kits are not considered magical tools when polypiling.
A tin of named monsters (e.g. Rodney) makes for nice trophies to ascend with.
Tinning in the Real World
Nethack's tinning kit is not considered a magical tool for purposes of polymorphing, but it is hard to say what kind of non-magical object(s) in the real world it is meant to correspond to. Home canning of meats is a fairly laborious process that involves cutting the meat into appropriate pieces, usually salting and partially cooking it, packing it into containers and then boiling the containers in a pressure cooker for over an hour. The pressure cooker is needed to raise the cooking temperature above 100 degrees C (212 degrees F), in order to eliminate dangerous microbes. This corresponds to the concept in NetHack of tinned food not rotting away. Home canning uses screw-top glass jars, but the NetHack tinning kit obviously uses tin cans, which further adds to the complexity, as the cans must be sealed. This is probably done by soldering the top onto the base, as was originally done with tin cans in our world. Canning guidelines from the United States Department of Agriculture are here. So, we can assume that the NetHack tinning kit includes the following:
- A large number of tin cans.
- Soldering supplies (presumably).
- A knife or knives for preparing the meat.
- A pressure canner.
- A good heat source, such as a propane burner, and fuel.
- Tongs, silicone gloves, or some other implements for handling the hot containers.
- (Maybe) salt.
- (Maybe) a frying pan, or some other implement for pre-cooking the meat.
The length of turn in NetHack is fairly abstract and flexible, and attempts to work this out will yield different results based on what kinds of activities (movement, combat, etc.) are used to calculate it. But, in light of the above, tinning a corpse is clearly one of the most action-packed turns a player will ever experience.
However, it never hurts to remember that NetHack is not real life.