Given 10 minutes and some acquacolor makeup, James P. "Jim" McGough can conjure a wicked-looking witch from any willing subject. In little more than an hour he can transform even the most clean-cut subject into a convincing Geico caveman, complete with glue-on 3-D brow piece.

As the wig master and makeup designer for the Virginia Opera, McGough spends his days creating alternative realities and putting the final touches to imaginary worlds. "A lot of singers thank me. It's the last piece in a character," he says in his studio, a few steps from the "Stage Right" entrance in the labyrinthine backstage of the Norfolk's Harrison Opera House. McGough is a master of the temporary disguise.

Wig blocks line the studio's shelves. They're all different sizes and labeled with the names of the characters they fit. McGough typically has a two-week window to make and perfect performers' wigs. When rehearsals start, he meets the actors for a measuring session. Placement of the hairline is key, so he measures from forehead to nape, then ear-to-ear over the top, and the circumference at the widest part of the head. "If we need, we pad out the block," he says. Accuracy is essential, as he may not see the performers again until the dress rehearsal.

At the central makeup station, four mirrors reflect back to four seats. At one, McGough's assistant Becky Scott works at the intricate, delicate task of creating a wig. She weaves a ventilating needle in and out of the cork-filled canvas with strands of hair so fine they're hard to see with the naked eye. "Give me needlepoint and I'd toss it across the room," she says. "This is therapeutic. It's like latch-hooking a rug." It takes about four or five ounces of natural hair to make each wig, using shades of natural blonds, reds and light browns. Five colors blend to create the tresses for Veronica Mitina, the soprano in the current show. On the top shelf are boxes of "rats," hairnets around ratted hair, which are used to create space without weight for a bouffant or beehive style, and also for buns. For men, the rats can be used to create an exaggerated 19th-century style in which the hair "flies out" at the sides.

It's a performance night — McGough's 11th "La Bohème" in his 22-year career. This is his 12th season with Virginia Opera, where he works from September to May; he then spends a month each summer with the Fort Worth Opera. "Every production is different, just always different," he says. The final look evolves from consulting with the director and the costume designer, talking about color and texture, and considering the libretto. McGough keeps a photo album of characters he's created that show all the wildly different interpretations. His Falstaff page shows close to a dozen contrasting styles. "It's important to be up on movies and TV programming for cultural references and to understand what the director is looking for" he says.

For this production, "It's mostly corrective beauty makeup," McGough says. One actor is playing two characters and must change from a disheveled young man, Benoît, to a distinguished older man, Alcindoro, in a matter of minutes. His look is planned accordingly, starting with slicked-back hair and stubble, created with a stipple sponge and applied with his foundation, then powdered all together. The between-acts transformation is choreographed by McGough and his assistant, a 20-minute process that involves creating a new persona reliant on the actor's facial hair and a different wig.

"Wigs are one way of creating a world," says McGough, who has male-pattern baldness and opts for a completely shaved scalp for himself. He cites a performance of "Tosca" when "a lot of the little boys were little girls." By putting them all in black wigs, they all looked uniform, he says. "They all become one thing. There's nothing to compare them with. It's another level of non-reality." Other tricks include using little strips of fabric to cover the eyes to simulate blindness, as required in "Turandot." He uses similar sleights of hand with makeup." For Madame Butterfly, there's an eye-lining trick on the lids and eyebrows that gives an Asian illusion, a suggestion," he says. "We use it even if the performer is Asian. That way we've created a world."

How to create a witch

Asked for a demonstration of his art, McGough corrals Scott. We ask for a quick-and-easy disguise, suited for a novice Halloween artist. He opts for a witch. He goes in search of his acquacolor, water-based makeup, which he keeps in a road box, like a giant shadow box, with row upon row of shades. "Most of it is foundation colors," he says, supplemented by character colors used for black eyes and the like. He favors products from Ben Nye ( www.bennye.com) and Kryolan ( www.kryolan.com).

• "We're going to make her green," he says, taking a small, synthetic sponge and moistening it in water. "Most people don't load up their brushes and sponges enough," he says. Then with bold strokes, and dabbing, he starts in the middle of her face and moves toward her hairline. "Always go from the center toward the edges to avoid streaking," he says. As he daubs on the makeup, he tells tales of Hollywood mishaps, of how Margaret Hamilton was "slightly green for six months" from her makeup in the "Wizard of Oz" and how Buddy Ebsen, who was the Tin Man, got lead poisoning from the makeup and had to be replaced with Jack Haley. Scott's whole face is now an even green. ("I've been kind to not put any on her neck, but I've done her jawline"" he says. He also opts not to do the tooth-blackening. "It's pretty horrifying. You have to dry the teeth and paint it on, then take it off with alcohol," he says.)

• "It's all about highlights and shadows," he says. He brings out the yellow, one of the colors in green. "We're going to bring out the angles on her forehead, and exaggerate her nose. We'll make it really angular," he says, adding a half-circle of light on her forehead, and blending the colors along the sides of her nose.

• He emphasizes that there are no instant results. "It's all in the layering. If you're using grease paint, then you need to add powder or it will come off. It's every bit as important," he insists.

• "Now we've got highlights and color, now we need shadow. For every highlight you have a shadow," he says. "I'm going to use black. It will look harsh, witches aren't happy people."

• Between her brows, he adds two black frown lines with a brush to make her look angry; then two lines to define her nostrils.

• He reaches for a six-compartment palette he has made up with male and female highlights, white, light brown, dark brown and black. He spritzes water into it, then lines her eyes with black and feathers her eyebrows.

• As a final touch, he adds black lipstick

• Then he whisks out a white-streaked black wig. "A wig is always the final touch," he says.

Minutes earlier, Scott had a fresh Irish-freckled look with her auburn hair drawn back out of the way of her work. Now, she has a fierce witch profile with hair to match. With the application of some cold cream followed by soap and water she restores her natural look within minutes.

News to Use

Here are some of McGough's makeup tips:

•Plan ahead and practice. Whatever you're going to do, do it a week before Halloween. That gives you time to ask questions if it doesn't work.