Painting photorealistic clouds in acrylic takes a degree of skill and an understanding of how clouds look in the sky. Clouds come in various shapes, sizes and colours, and to make them look like a photo involves determining the weather in your painting, which will determine the type of cloud you will paint. Notice that clouds are not always pure white. The direction the light hits the clouds in your painting as well as the time of day will help determine what colours you will use in your cloud.
Position your cloud photo so that you can see it easily and refer to it often.
Load your artist's palette with a generous amount of titanium white, a dollop of blue and a small amount of black. If your clouds have other colours, you can add those to the palette later. Use a ½-inch round tipped brush and load it with the white paint.
Determine which direction your light source is coming from. This side of the cloud will be the brightest white.
Make a small, solid circle of white in your sky, and with a scrubbing motion begin to move the paint out and away from the original circle. Push the paint around in all directions creating a transparent shape. Some sky will begin to show through.
Work the white outward to make the edges of the clouds nonuniform. Edges should be soft in all directions and not sharp and defined.
Make the paint go as far as possible before adding any more paint to the brush. The edges of the cloud should look hazy, and the inside of the cloud should have shadow coming through.
Reload your brush with paint and make some circular contours at the top of the cloud. Wipe off your brush. Blend the contours down and across the cloud. This will create the look of light and shadow. Most of the middle of the cloud should be solid. Use the other colours on your palette to make highlights near the edges of the cloud and in the areas where the light is hitting the cloud. Blend all contours down and across your cloud.
Add break-off clouds at either end of your cloud to make the cloud look like it is moving through the atmosphere.