What's going on, am I doing something wrong? I finally worked my Enchanting up to 100 and chose the Extra Effect perk but, when I tried to double-enchant an item, none of my previously single-enchanted items showed up as a choice to be enchanted. Is there something special I'm supposed to do past using the Enchanting Table in the normal way?

You can't double enchant something that already has an enchantment on it, I'm pretty sure.

You can enchant an item only once.

You can't do that.

EDIT : You have to put them both on at the same time.

EDIT : Even then, it cannot be the same enchantment.

you can only put 2 enchants on an un-enchanted weapon you cannot add to existing enchantments

Not according to the perk itself or the Skyrim Official Game Guide (page 23). The perk states under it in the perk tree in-game "Can put two enchantments on the same item", and the game guide says the same thing. The game guide reads:

Can put two enchantments on the same item.
Requires: Enchanting 100, Storm Enchanter (I have) OR Corpus Enchanter (I have)
Extra Effect allows you to apply two enchantments to any item. Double-enchant everything you have, and you'll notice a tremendous leap in your power level!

Tried that. Doesn't work.

You tried getting an item without enchantments and then adding two different enchantments to it at the same time, and it didn't work? Because it should, and that's also by the way the only option you really have.

Empty items, add both at the same time.

You know, I didn't! I was assuming each enchantment required a separate soul gem. Are you saying you can place two enchantments using only one soul gem?

That is correct.

That's right. Two for one my friend.

This is just a mistake in the game guide, if you interpret it literally. You can't put two enchantments on a leg of goat roast, for example. When you enchant an unenchanted item for the first time, you can put two effects on it. End of story.

Thanks for all the help, everyone! I am now happily double-enchanting away. I was rather disappointed that I couldn't add enchantments to previously enchanted items, since making new armor and weapons was a bit of an inconvenience but, since my Smithing's at 100, too, I was able to remake versions of everything I had been using.

On a different note, are there enchanted items that buff Enchanting? All I've seen so far are potions. I've been able to buff my armor and weapons a huge amount by wearing a 4-piece outfit enchanted with Smithing. Seems there should be some way to get the enchantments I put on items up as high as items I randomly find (like 70% Fire Resist, I can only enchant to 46%, or 40 or better Carry-Weight, I can only manage 37, for instance). It would be nice now especially, since I can double-enchant.

Nope, no enchanted items for enchanting. Only potions, as far as I can tell. Just like there's no no potions to increase alchemy.

An enchanted item that let you make better enchantments would immediately lead to a loop. There is actually a loop though if you add alchemy, though it must be a lot of trouble.

I think there are only potions, because if you were able to enchant items with better enchanting enchantments (still following?), you'd be able to keep improving those enchantments infinitely

started to see how far you could go. I got as far as fortify enchanting 66%, before I got bored and went back to playing the game.

Where did you find an item like that, or are you talking about a potion? I haven't taken my Alchemy up to 100 yet. Gold is so easy to get, I just buy potions I need.

Why? From what I can see, the power of the item you destroy in order to learn the enchantment doesn't have anything to do with the final power of your enchantment, which seems to be controlled by only your Enchanting skill. At least that's been true with Fortify Carry Weight, Fortify Magicka, Fortify Magicka Regen, & things like that.

Ya see, the double enchantin' perk is dividing the soul inta two halves

So one enchantment is pissed off

While the other is confused

You could say that the Skyrim forums are double-enchanted as well

Danm well there goes that character concept I was going to rule with my leg of lamb...

I'm going to check out the everything-in-the-game room again and look at the Enchanted Items...

Imagine there is a 'Fortify Enchanting' enchantment, you've learned it, and now you're enchanting, say, a helmet with it. You get something like a +50% Enchanting helmet. Now you use that helmet to enchant another item with the same enchantment, now the helmet makes the maximum higher, and so on and so on.

Unless you're saying a Fortify Enchanting potion doesn't affect Fortify Carry Weight etc., so that helmet wouldn't affect it either. And in that case, what does the potion actually do then?

Not disenchant loop, just enchant entanting gear to get + to what you enchant... making better enchanting gear. Wear that and make better still. Keep repeating and you'd have a necklace, robe, gloves, and circlet EACH with +100% enchanting 9or however high you wanted to go)

This is still doable, but requires Alchemy.

You can enchant +alchemy gear to make stronger +enchant potions. Use the +Enchant potion to make better +alchemy gear, which makes even BETTER enchant potions.

Rinse and repeat until you get the aforementioned +100% to alchemy on each item (+400%) or however high you want to go, and using that to make +Enchant potions to make stronger enchanted weapons and armor.

Oh... and for the record... Enchanting @ 100 is plenty strong enough as is without needing to exploit the Alchemy/Enchant loop.