Museums have the system down pat, as do decorators. Hanging pictures on a wall is a science. Balance, spatial unity and proper layering are the technical aspects, while comfortable viewing of the collection is the variable. Avoid a jumble on your walls by pre-arranging your grouping. Keep in mind where you plan to hang the collection, the immediate environment, the purpose of the grouping, and which piece or pieces are the center of attention.
Horizontal Center Line Theory
Arrange picture groups as a horizontal strip or a vertical stack, but hanging in either manner means adhering to a geometric plan. Museums use a center line theory to hang pictures horizontally because paintings vary in size. Choose where you want your grouping to hang and draw a horizontal line from left to right. Assemble the pictures on the floor until you're satisfied with the arrangement, adjusting for frame style and size. Position the art on the wall, with the line going through the center of each piece. It doesn't matter how high or low the picture lays in relation to the line. Once hung, the center line grounds your collection. Depending on the quantity of pictures, space them 2 to 5 inches apart.
Choosing Pictures to Stack
Before slapping a bunch of pictures on a wall, consider the subject matter of the pictures, the color of their frames, the matting and the art itself. Your collection needs unity. If it's a disparate group of art, consider reframing all of it in similar colors, so the collection doesn't come off as a hodge-podge. Lay the pictures out on the floor, placing the heaviest either on the left, if it's counterbalanced with another heavy piece that hangs on the right, or put the heaviest in the middle if all the others are smaller. A stack displays better if the number of pictures is odd. An even number shows best in a rectangular display.
Organizing the Stack
You can either use paper cutouts the same size as your pictures to test-drive your layout, or eyeball the placement as it lays on the floor. Both require exact measurements. Establish a center line for your left picture and place the others either on, above or below the line with equal spacing. Not all of your grouping needs to be pictures. You can add objects as long as they coincide with your theme and are hung according to your plan. Maintain balance from left to right.
Layering the Pieces
A mantel is an ideal location to display groups of art, especially if the art is small. Place the largest piece in the back as you begin your layer, and work forward with the different sizes and shapes. An odd number of items works best, and adding mementos or small statuary adds interest.
Hanging art is personal. It's customary to place the main piece at eye level with the occupant of the home or the hostess. Groupings hung over a sofa should equal the length of the sofa or be no less than 2/3 the length of it. The bottom of the frame should be 8 to 10 inches above the back of the sofa. Don't hang any grouping so high it causes viewers to stretch their necks to appreciate your art.
When seated, especially in the dining or living rooms, a grouping of pictures carefully placed at eye level from the seat is an artistic surprise. Pictures hung up a staircase need precision and conformity. Keep the topics similar, the frames color-coordinated, and the spacing equal. A center line drawn up the staircase anchors the display.