Other factors in determining alchemy outcome

Steady - If a weapon has this attribute in blue letters at the bottom of its
description and stats, a failed alchemy attempt will prevent this item from
losing durability. It will NOT, however, prevent it from breaking if that
happened to be the result of the failed upgrade roll. Breaking is generally
rare and has not yet happened to me.

Immortal - If a weapon has this attribute in blue letters at the bottom of its
description and stats, a failed alchemy attempt will prevent this item from
being destroyed. An incredibly useful stat, however it only has limited uses.
(i.e. Immortal/2 times) Immortal will NOT prevent an item from losing
durability if that's what the failed upgrade roll happened to be.

Lucky - Increases chances of successful alchemy. Far and away the best
modifier to have on a weapon, in my opinion.

Astral - This magical attribute came out with the 6/20/06 update, and has the
ability to prevent unsuccessful attribute enchancing from decreasing the stats
of your weapon. Successful attribute enhance does not reduce the astral value
of the equipment.
http://www.gamefaqs.com/computer/doswin/file/930711/43300