According to most dictionaries, the preferred verb is to sculpture, same as the noun. Sculpt is a back-formation, which was first noticed by an observant lexicographer in 1864. Sculp, says Bryan Garner in A Dictionary of Modern American Usage is a “needless variant” of sculpt.
But the big Webster’s says sculp is both “obsolete” and “humorous,” and, furthermore, says the word also means to remove the skin and blubber of a seal or to break slate into slabs. The Oxford English Dictionary finds that sculp was used as early as 1784, so it predates sculpt by sixty years. The OED labels sculp as “jocular” and sculpt as “ludicrous,” so maybe we’d just better say carve and let it go at that.
The sculptured visage of the Bard of Buffalo Bayou was frozen in a maniacal rictus when he read over these lines before forwarding them in a plain brown envelope for publication:
A sculptor who was brave and gallant,
Did not possess a crumb of talent.
His carving of a local hero
Would barely earn a grade of zero.
The patron viewed it with dismay,
And angrily refused to pay.
The sculptor said, “I want what’s due,
So I’m afraid I’ll have to sue.”
And when the suit wound up in court,
The judge dismissed it with a snort,
Invoking, in his observations,
The sculptor’s Statue of Limitations.