blessed modify scroll. does not destroy a base item that you want to use to extract the appearance from.
But it only works from a normal item, not an item that already has an appearance on it.
For instance, I have an Apoc. 2hand sword with a Lava Saw appearance, but I cant extract the Lava Saw appearance from that weapon to put it on another because my base weapon is not a real Lava Saw.