Protecting an item from damage

[Tr011]

What ways are there?
I know making it a good material (i.e. Riverine from Stormwrack or Obdurium from Stronghold Builder's Guide), then the Hardening Spell (from SRD) for half CL as hardness.
Making it a magic weapon/armor gives +1 HP and hardness for every +1 enhancement.

[Jackinthegreen]

Dwarvencraft from RoS helps out too, plus a couple templates in DMG2 increase HP or hardness.

[zook1shoe]

And that metal, from BoED, that as a full-round action can fully restore a sundered item

Glassteel is cheaper adamantine

[kharmakazy]

Doesn't aurorum just reform if broken? Aurorum (BoED, 38) 4000 gold

[zook1shoe]

I'm afb, but I thought it was an action not automatic

[NiteCyper]

For phylacteries:

Once per day as a full round action, you can improve the sturdiness and durability of one building, piece of sculpture, piece of furniture, or other constructed object. To do this, you must spend the full round touching the object in question. At the end of that period, the object gains a number of hit points equal to your character level, which may make the object better than new, even more sturdy than when it was first constructed.

Repeat ad nauseam.

The Recharge Condition isn't dangerous either and is indefinitely redoable.

Stop the equation, then restart its progress by carving the next three symbols yourself. This requires a DC 15 Intelligence check or a DC 25 Knowledge (the planes) check.

It's not necessary to [have] a touchstone [feat] to earn a touchstone's Higher-Order Ability.

It's a lot for a little, but meh, it's something.

Touchstones are like old-school versions of Magical locations, or vice-versa.

Doesn't aurorum just reform if broken? Aurorum (BoED, 38) 4000 gold

I'm afb, but I thought it was an action not automatic

An aurorum weapon, shield, or suit of armor that has been sundered can be reformed by bringing together its fragments (a full-round action).

[Maat Mons]

Here's what I have saved from when I was looking into the hardness of bows specifically:

(click to show/hide)

Bow Hardness

Crystal of Adamant Weaponry: This weapon augment crystal gives a weapon +2 hardness for 300 gp (least), +5 hardness for 1,400 gp (lesser), or +10 hardness for 3,400 gp (greater).  (Magic Item Compendium 64)

Deep Crystal: This special material gives a bow 10 hardness and 15 hit points (instead of 5 hardness and 5 hit points) for +1,000 gp.  Deep crystal is a mineral, and deep crystal armor “is considered to be made out of metal,” so you could plausibly argue for applying dwarvencraft to a deep crystal item.  (Expanded Psionics Handbook 182)

Densewood: This special material gives a bow 8 hardness and 10 hit points (instead of 5 hardness and 5 hit points) for double the base cost. (Eberron Campaign Setting 126)

Dragonbone Bow: This gives a bow +20 feet range increment for +100 gp.  I had trouble finding this, but Dungeon Master's Guide has the statistics for bone on page 144.  The bow has 6 hardness and 5 hit points.  (Draconomicon 117)

Dwarvencraft: This gives a weapon +2 hardness, +10 hit points, and +2 saves for +600 gp.  It must be made of metal or stone, so I don't know how to get it on a bow, but a way might exist.  (Races of Stone 159)

Enhancement Bonus: Each +1 of enhancement bonus adds +2 to a weapon’s or shield’s hardness and +10 to its hit points.  (Dungeon Master's Guide 217 and 222 [see errata])

Hardening: This permanent spell improves an object's hardness by +1 per 2 caster levels.  It's 6th level and requires a 50 gp component, so paying a 20th level NPC wizard to cast it costs 1,250 gp (and results in +10 hardness).  (Spell Compendium 109)

Matter Manipulation: This instantaneous power improves an object's hardness and hit points.  This is expensive, but the 15 cubic feet of material affected (at minimum manifester level) can be made into quite a few bows.  (The best figure I can find for the size of the piece of wood you start with to make a longbow is 6 feet by 1 inch by 2 inches, so 180 bows.)  You may be able to buy a piece of wood affected by the power for a fraction of the cost of an NPC manifestation of the power.  (Expanded Psionics Handbook 115)

Soulforged: This weapon template gives a weapon +1 hardness and +5 hit points for +800 gp.  It must be made on the Seven Mounting Heavens of Celestia by a native.  The description notes that most soulforged weapons are made by the spirits of dwarven smiths, so it should be compatible with dwarvencraft.  (Dungeon Master's Guide II 279)

Sovereign Sealant: This gives a wooden item it's applied to +2 hardness.  A drum costs 8,000 gp but is enough to treat a huge object, so you can presumably treat multiple bows.  (Stormwrack 134)

There's also some stuff here.  In particular, I draw your attention to pure ore and oerthblood, both of which double the hardness of a metal they're mixed with.  Also, obdurium (Stronghold Builder's Guide, p35) has hardness 30.  [Oops, you already had that listed.] 

[zook1shoe]

Thanks NiteCypher

[Zionpopsickle]

Step 1: Make item immune to acid
Step 2: Store inside Tarrasque
Step 3: ????
Step 4: Profit

[kharmakazy]

Being magical affords items some protections over mundane. Animated and haunt shifted items are probably less likely to be damaged due to being able to move on their own.