For some years now, German-born artist Kerstin Rost, 42, has been fighting formalism. Armed with photographs, paints and silk screen, she has steadily confounded the often severe style and rigid simplicity of artists who believed they had found a formula for everything. While Josef Albers or Victor Vasarely might finish their cubes, squares and other geometric forms to near-sterile perfection, Rost gleefully destroys symmetry any way she can. Incongruity and humor are her modus operandi.

In her forthcoming show, opening Saturday at the Marsha Mateyka Gallery (2012 R St. NW), Rost has undertaken to make the great stylist Mondrian spin in his primary-colored grave. The well-known originator of the arcane and purportedly mathematically-based Neoplasticism suffers mightily at her playful hands -- one of his compositions is relegated to the bottom of a sardine can, and another has been carefully reproduced but for a giant, grubby thumb print.

"The stylists seemed to have this idea that everything should be totally impersonal," says Rost. "So with the thumb print I say, 'Here, now I have personalized it!' I had a lot of fun doing this series -- poking fun at the seriousness of formalized esthetics.

"A few years ago I went through this phase where I found I had a hang-up with formalism. I reconciled that by dealing with Mondrian. My reaction to Mondrian was -- partially, I really liked him. He carried painting to a radical point of reduction . But he annoyed me because of the precision of his icons. I wanted to make some of his rigid lines fluid. He was trying too hard to reduce art to an absolute formula. Things like absolute truth and absolute beauty are just not valid anymore. There is no absolute esthetic. The world is in flux."

But with these paintings, photographs and silk screens, Rost is dealing with more than just formalism. She is, like many other artists today, trying to determine the validity of the reproduced image. In other words, is a Mondrian that has been faithfully reproduced on a T-shirt still valid as art? Or does the fact that it has been reproduced reduce it to mere design?

"I think the art world is extremely confusing right now," says Rost. "People are having trouble sorting out what is gallery hype, and what the artists are actually working toward. With the Mondrian series, I am taking art images which have become very popular and giving them a twist -- trying to somehow deal with the stereotype."

And she has been dealing with some of the same sort of questions on a more fundamental level, in the very mediums she employs. For the past three years she has been attempting to reconcile an age-old question: Which is a more valid means of rendering a figurative image: photography or painting?

Rost has decided on both -- simultaneously.

"I started working with black and white photography three years ago in Du sseldorf. The more I became interested in photography, the more I began to feel that just painting was not enough. It's a question of what do you paint, and what do you photograph? Man Ray said he painted what he couldn't photograph, and photographed what he couldn't paint. So I began combining the two on canvas. I think this method is much more valid than photorealism. I question the validity of painstakingly reproducing a photo in paint.

"The dialogue is, what is painting and what is photography? It is largely a question of the content of the picture. Content and shape form the image. The content and the organization unite to form the painting. They go hand in hand. There are a lot of random things that happen when I transform a photographic image into silk screen for the canvas. I let the accidents happen. I let the picture evolve as I am doing it. That is the reconciliation right there."

The Mondrian series combines both mediums to achieve a range of textural and thematic nuances. In these pictures one can easily detect Rost's admiration for the painter whose name comes most often to her lips -- Robert Rauschenberg, another artist who has for some time been combining photography, painting and printing. And though this sort of "reconciliation" runs the risk of becoming an intellectual exercise -- at the cost of esthetic or emotional input -- Rost seems to pull it off. The one uniting element in all of her work is humor.

"Just to express yourself is not enough," says Rost, "no matter what medium you use. Crying is expressing yourself, but it means nothing to anyone else. You have to distill things and contribute something. Whatever you do must transcend being an ego-trip for yourself. Humor is a wonderful thing for distilling serious considerations.

"I believe you need humor -- even in the most serious of work."