Surely the tumbledown storefront that houses the main branch of the ILK co-op on the increasingly gentrified Santa Fe Drive gives no indication that inside, as often as not, are some of the best art shows in town. That was definitely the case early this spring when the south gallery was swept clean, painted, and given over to Untitled: Steven Altman, a solo show that featured some of this highly regarded Denver painter's latest abstractions. And they were sensational. Altman first lays a grid of paper on a board, then paints over it in a gestural style; his unerring sense of composition and striking juxtapositions of color provided this show with a number of breathtaking moments.