What portion of the crafting time for a magic item does an artificer need to meet the minimum caster level?

Question

The artificer class has multiple abilities related to emulating spell casting abilities for crafting items and meeting the caster level requirements for crafting items. First, they have an ability to take crafting feats that would otherwise require a caster level two higher than their artificer class level. Second, they can craft items at a caster level equal to their class level, even when that would otherwise be one or two levels below the minimum caster level for creating that item. And third, they are able to use the Use Magic Device skill to emulate having cast a spell to include its effect in a magic item. It is also noteworthy that the artificer only has to succeed at this check once, regardless of how many days it takes to craft their item.

However, the class description also contains this text: "He must meet the caster level prerequisite, including the minimum level to cast a spell he stores in a potion, wand, or scroll."

Is this simply restating the fact that an artificer's class level sets the cap for the caster level of the effect they put into an item? Or is this somehow setting another precedent for requirements when crafting items? To phrase it another way, is the artificer required to meet this caster level throughout the entire time they're crafting the item, or just when making the use magic device check to emulate casting a spell? Taking the question further, is it possible for an artificer to utilize effects such as the spells Create Magic Tattoo or Suffer the Flesh to temporarily increase their caster level, or would they need to utilize a longer lasting item, such as an Orange Ioun Stone?

I know that regular spell casters are required to cast all spell prerequisites once per day when crafting, which would by nature require them to meet the minimum caster level every time. However it strikes me as odd that the artificial only needs to succeed at the check once, and then they never need to attempt it again. Also when using a Dedicated Wright the homunculus's creator only needs to channel each spell once, which seems similar to this.

Answer 1

The Dungeon Master Guide had some errata that removed the Caster Level requirement when making magic items.

http://dnd.etherealspheres.com/eBooks/DnD_3.5/core/Errata/Dungeon%20Master%20Guide-Errata.pdf

The last two sentences in the section on Caster Level are ambiguous and potentially misleading.

Replace with this text: For other magic items, the caster level is determined by the creator. The minimum caster level is that which is needed to meet the prerequisites given.

The original text made the caster level a requirement.

Page 215: For other magic items, the caster level is determined by the item itself. In this case, the creator’s caster level must be as high as the item’s caster level (and prerequisites may effectively put a higher minimum on the creator’s level).

The sentence you quoted

He must meet the caster level prerequisite, including the minimum level to cast a spell he stores in a potion, wand, or scroll.

has two meanings. First it reinstates the requirement you need to match the caster level of the item to create it. Second it clarifies the caster level minimum of the spell in potions, wands and scrolls are required.

Your question:

the artificer required to meet this caster level throughout the entire time they're crafting the item, or just when making the use magic device check to emulate casting a spell?

You need to have it the full duration of the crafting (8 hours) because you are not casting a spell. You are expending a slot. Things like orange ioun stone will work, because it is considered a permanent increase to your caster level after being worn for 24 hours. Temporary increases will not work.