Can the Hardening Spell Stack?

[Talon881]

Pretty much what it says on the tin.

https://www.d20pfsrd.com/magic/all-spells/h/hardening/

It says it is a permanent effect, but is there anything in the rules that states that a permanent spell cannot be applied more than once?

[Derklord]

"Stacking Effects: Spells that provide bonuses or penalties on attack rolls, damage rolls, saving throws, and other attributes usually do not stack with themselves." CRB pg. 209

The increase to hardness may not be called a bonus, but the official position is to to apply the principle to anything similar.

[Belafon]

It is worth noting that spell was in the book "Pathfinder Campaign Setting." That book was written under 3.5 rules, not Pathfinder. I never played 3.5 but you'd need to go back to those books for a "by the rules" answer.

The "voice of sanity" answer is that no, it shouldn't stack. Otherwise there would be a fair number of weapons, armor and other items in the world that - while theoretically breakable - are for all practical purposes invulnerable.

[Taja the Barbarian]

As a general rule, bonuses do not stack with themselves:

Combining Magic Effects wrote:

Source PRPG Core Rulebook pg. 208

Spells or magical effects usually work as described, no matter how many other spells or magical effects happen to be operating in the same area or on the same recipient. Except in special cases, a spell does not affect the way another spell operates. Whenever a spell has a specific effect on other spells, the spell description explains that effect. Several other general rules apply when spells or magical effects operate in the same place:

Stacking Effects: Spells that provide bonuses or penalties on attack rolls, damage rolls, saving throws, and other attributes usually do not stack with themselves. More generally, two bonuses of the same type don’t stack even if they come from different spells (or from effects other than spells; see Bonus Types, above).

So no, a spell that increases an item's hardness shouldn't increase the hardness any further with additional castings...

As noted earlier, Hardening is actually a D&D3.5 spell so 100% compatibility with PF1 is not guaranteed...