CAMBRIDGE — Artist Duron Lewis uses paint, pastels and pencils in his art, but his preferred medium these days is fire. Well, not that you could create a picture with fire and have it hanging on your wall without causing great damage — Duron Lewis uses soot from the fire to create his images. Still, he calls his not very new medium “fire painting” because where there’s soot, there was or is fire. Mr. Lewis tells the story that soot from fires was used in cave paintings millions of years ago, and that he is the first modern artist to bring fire back out of the caves and onto the canvas. A resident of Enid, Okla., Duron Lewis came to Cambridge with a present for the Harriet Tubman Museum, and spent some time explaining his techniques and demonstrating them to an interested audience. Artist Lewis uses a candle or a kerosene lamp to produce different quantities and patterns of soot onto a prepared canvas. Once the soot is built up to a desired thickness and shape, he then uses a dry paintbrush, a feather, a blade or other tools to remove and shape the soot patterns to create a picture. In a few minutes, working on an upside down canvas, Mr. Lewis had created the basics of a face on the sooted canvas. He explained how delicate the process is, yet forgiving since more soot can be added to soften edges or even wipe out a mistake. On display he had a number of small fire-paintings of automobiles, portraits and more. “I have always been in awe of Harriet Tubman,” Mr. Lewis said before he unveiled the painting. “And I’m proud to donate this painting to an organization that promotes Harriet Tubman’s legacy.” He was also thrilled and humbled to be in the presence of two of Harriet Ross Tubman’s blood relatives, her great-great-grand-niece Valery Ross Manokey, and Charles Ross, Ms. Manokey’s nephew. Mr. Lewis, in keeping with the “fire” theme in his work, creates fire paintings for the benefit of EMS and fire departments across the nation. He told a story about his early impressions of fire trucks, and said that the image and respect for firefighters has always stayed with him. To give back, he is traveling to fire companies in different states, and donating paintings of their personnel and equipment. To fund this, he has started a GoFundMe account to receive donations to help pay for his work. To contribute, go to www.gofundme.com/jsvh4zgc, or Google GoFundMe and search for Duron Lewis on the GoFundMe site. Duron Lewis can be contacted at two e-mail addresses: DLpencilworks@gmail.com, or DKLewisArtStudios@gmail.com. His website is www.dklewis.net, and you can call him at 580-747-0667.