What does the enhancement bonus of Blue Ice stack with?

Question

Frostburn lists Blue Ice as an Exotic material (p. 80). It weighs half as much as iron and can be forged, shaped and utilized as if it were iron. (Very useful to keep your beer cold!)

When forged into a slashing weapon it has a +1 enhancement bonus on damage.

If I were to create a masterwork blue ice long sword, would it be the same as a +1 blue ice long sword — with +1 to attack and +1 to damage — just non-magical?

If the weapon were magical, would this enhancement bonus stack with the magic bonus? For example, would a +2 blue ice long sword give a +2 to attack and +3 to damage?

(Please support answers with references, preferably from rulebooks.)

Answer 1

If I were to crate a masterwork blue ice long sword, would it be the same as +1 blue ice long sword? (Minus it being magical) +1 to touch and +1 to damage?

For the purposes of attack and damage rolls, yes. For most other purposes, no.

The issue is that while attack rolls with the weapon have a +1 enhancement bonus, and damage rolls with the weapon have a +1 enhancement bonus, this is not the same as the weapon itself having a +1 enhancement bonus. Enhancement bonuses to weapons add enhancement bonuses of the same value to attack and damage rolls, but they do more than that. They increase the weapon’s hardness, they allow the use of weapon augment crystals, and so on.

The weapon is also not magical. It’s not subject to dispel magic, but it doesn’t overcome DR as a magic weapon would, either. It has no chance to glow (as 30% of magic weapons do). Anything that talks about magic weapons isn’t talking about a masterwork blue ice weapon.

Does this enhancement stack if the weapon were to be magical, say a +2 blue ice long sword. Giving a +2 to attack and +3 to damage?

No. Both the enhancement bonus to a magic weapon and the blue ice apply an enhancement bonus to damage rolls; enhancement bonuses never stack.

Magic weapons have enhancement bonuses ranging from +1 to +5. They apply these bonuses to both attack and damage rolls when used in combat.

^{(emphasis mine; the bonus is not just the number, but the type too.)}

Enhancement bonus

An enhancement bonus represents an increase in the sturdiness and/or effectiveness of armor or natural armor, or the effectiveness of a weapon, or a general bonus to an ability score. Multiple enhancement bonuses on the same object (in the case of armor and weapons), creature (in the case of natural armor), or ability score do not stack. Only the highest enhancement bonus applies. Since enhancement bonuses to armor or natural armor effectively increase the armor or natural armor's bonus to AC, they don't apply against touch attacks.

Answer 2

Yes, a masterwork blue ice longsword is mostly equivalent to a +1 longsword.

As you said, blue ice slashing weapons give +1 damage, and masterwork weapons give +1 attack. A +1 magic weapon gives +1 damage and +1 attack, so a masterwork blue ice weapon gives the same attack & damage bonuses as a +1 magic weapon of the same type (assuming it's a slashing weapon).

It's still not a magic weapon, though, so it's missing the other effects of magic on weapons. Most of those you wouldn't care about (the glow) or are actually good (not subject to Dispel Magic or antimagic fields), but it does mean your longsword won't bypass DR/magic damage reduction.

No, the bonuses do not stack.

From the PHB, p171:

Bonus Types: ... The important aspect of bonus types is that two bonuses of the same type don't generally stack. With the exception of dodge bonuses, most circumstance bonuses, and racial bonuses, only the better bonus works. ...

From the DMG, p221:

Weapons: ... Magic weapons have enhancement bonuses ranging from +1 to +5. They apply these bonuses to both attack and damage rolls when used in combat. All magic weapons are also masterwork weapons, but their master bonus on attack rolls does not stack with their enhancement bonus on attack rolls. ...

Magic weapons give enhancement bonuses to damage. Slashing blue ice weapons give enhancement bonuses to damage. Enhancement bonuses do not stack. Therefore a magic blue ice slashing weapon would only receive the higher of the two enhancement bonuses to damage.