Howardena Pindell’s 23 mixed-media works at G.R. N’Namdi span three decades and range intriguingly from intimate, playful explorations of process to large pieces with ardent social and political messages. In all of these works, Ms. Pindell’s feelings amply come through, whether celebratory or censorious. Her messages, however, sometimes struggle with art’s rhetorical limitations, and require lengthy wall texts by way of explanation.

In the 1970s, the artist experimented with assemblages of countless tiny paper circles, their lively surfaces often enhanced by bright colors and grids of thread. A single untitled work from this period — a pale blue irregular square inscribed with tiny arrows and numbers — suggests a delicate, cryptic map.

Ms. Pindell’s priorities evolved after a serious automobile accident in 1979. A black woman, she expressed her indignation toward racial discrimination in the video “Free, White, and 21” (1980), a stinging portrayal of white condescension toward blacks. (The video will be presented at the gallery between 6 p.m. and 9 p.m. on July 26.)

In the 1980s, the artist embarked on a series of large, flat, irregularly shaped works made from pieces of canvas stitched together and covered with exuberant dabs of paint. The 7-foot-wide, roughly circular “Autobiography: Earth/Eyes/Injuries” (1987) commemorates her accident with a tapestry-like surface of intense red, ultramarine, and cerulean blue strokes. A closer look shows the outline of the artist’s own figure in the seams. Like many works here, it incorporates small photographs that have been cut into strips, with painted images filling in alternate strips; here, they represent the eyes and faces of witnesses to her accident, as explained by the accompanying wall text.

The three rounding, connected portions of “Lash/Slave Memorial” (1998–99) provide a dynamic visual flow for its message. Various African masks fill the left section; the center, criss-crossed by chains, suggests bondage and the torturous voyage linking Africa and America. Floating amidst the chains are tiny, chilling diagrams of slave ships’ decks, with humans crammed head to foot, from bow to stern. The names of destination ports fill the right section, along with the names of African-American inventors, listed on the accompanying handout. These men and women were responsible for hundreds of inventions, ranging from the bicycle frame to the truck refrigeration unit, poignantly contrasting blacks’ creative prowess with slavery’s bestial purposes.

The more somber “Separate but Equal: Genocide AIDS” (1990–92) lists the names of children afflicted with AIDS on the stripes of twin versions of the U.S. flag, one white and one black. We learn that Ms. Pindell’s cousin observed the superior medical treatment for the white children — symbolized by the segregated stripes — during his treatment for AIDS.

Ms. Pindell’s message becomes less convincing when she interpolates universal motivations from single acts of bias. “Who Do You Think You Are? One of Us?” (1991–92), was inspired by her teenage memories of a white acquaintance’s taunts.The witnessing eyes return, this time in sections of yellow and greenish-blue canvas radiating from a central gray labeled with the words “racism,” “assumed privilege,” and “appropriated culture.” The bright colors and textures seem celebratory, but the wall text, after describing the original taunt, lists at agonized — and agonizing — length some of the double standards of the “American system of apartheid.” (No. 1: The empowered generally stereotype people of color as “dirty and lazy.” No. 6: “Our success will be criminalized.You will dwell on our failures and if you cannot find any, you will make some up …”)

Ms. Pindell turns to darker, sinister hues in some of her more recent political work. “In My Lifetime” (1995–96), produced in response to the Gulf war, depicts mushroom clouds, maimed men and children, and the captions “Hiroshima,” “Nagasaki,” “Iraq,” and “Angola.” The wall text decries all these events equally, while explaining how a reallife Bible placed on a tree stump before the canvas represents the misuse of religion and the environment. A similar, roving outrage informs “Coup” (2000–06), which features the second President Bush’s face on a blackened surface surrounded by phrases like “war crimes,” “rendition,” and “4th Reich.” Next to it, a life-size, in-the-round black skeleton hangs in a black net.

It’s a little surprising, then, to see the artist return to something like spontaneous pleasure in several small drawings from 2003. Inspired by astronomical photographs, they swarm with tiny arrows and digits that seem like nests of tidy organic forces. This contrast between her small works’ spry curiosity and the heavy-handed symbols of some of her political work reflects the difficulties of combining art and advocacy. Art, like Picasso’s “Guernica,” measures a powerful personal response; advocacy, on the other hand, makes an explicit case. When Ms. Pindell’s wall text makes the case for her symbols, they tend to be reduced to visual accessories.

Moreover, the juxtaposing of scenes from Hiroshima and Angola won’t look like reasoned debate to every viewer. Ms. Pindell’s messages strike home most forcefully in bits of actual documentation: the slave ship’s floorplan, for instance, or the photograph of a man — shackled hand and foot, a collar with two-foot barbs locked around his neck — adorning a book cover in “Slavery Memorial/Narratives” (1998–99).

Turn the pages of this book (“Slave Testimony: Two Centuries of Letters, Speeches, Interviews, and Autobiographies,” edited by John W. Blassingame) for eloquent accounts of the appalling. In 1854, Stephen Pembroke recounted: “The slave never knows when he is to be seized and scourged … My first wife was a slave; so my five children are slaves too … [my sons] were twice sold before my face … I know one man who gave his slave one hundred and fifty lashes in two days, and on the third he died. He’d crept into the field; and his master, supposing he was sleeping, went up and cowhided him, but he was cowhiding a corpse …”

Until August 31 (526 West 26th Street, between Tenth and Eleventh Avenues, 212-929-6645). Prices: $1,800–$100,000.