Arthur Guptill Renders a Window

In 1935, Arthur Guptill demonstrated a sequential method frequently used by architectural illustrators for painting a window. 

Guptill first draws the subject in pencil, giving careful attention to the perspective. 

He rules the lines of the shutters very evenly. Then he lays down a warm wash in watercolor over the wall and the curtains, and sets up variegated flat colors for the stonework. He washes in the shutters in green.

The dark interior spaces are painted over the mullions, but not the sash. The dull orange color of the interior gives a feeling of depth and transparency.

Next come the shadows cast on the curtains and the shade from the sunlight coming from the upper left. He then adds the darks of the mullions and the outer moldings with a ruling pen.

If you're not familiar with a ruling pen, it's a tool for drawing a line of constant width, usually guided by a ruler that's raised a bit off the surface. It has two sharpened metal tips that taper together. The spacing of the gap between the tips governs the width of the line.

That gap is controlled by an adjustable wheel on the side. Ink or watercolor, applied by an eyedropper (Edit: or a brush), sits in the gap and flows by capillary action.

Guptill then draws mullions with the ruling pen filled with opaque white watercolor, slightly yellowed. The consistency has to be just right. Too wet and it puddles out; too dry and it won't flow at all. When a ruling pen works well, it's a joyful feeling.

Edit: After reading the post, blog reader Glenn Tait got out two of his old Kern ruling pens, ran some tests, and sent the photo, saying: "By rote, after so many years, I filled the pen by loading my brush (using M. Graham watercolors) and pulled it across the open side of the pen to fill it then, after adjusting the tip width, dragged it a bit along my left forefinger to get the flow started. The watercolour works great."
Thanks, Glenn. I'm going to throw one in my sketch kit, too.
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Arthur Guptill's classic book about rendering architecture in watercolor is called Color in Sketching and Rendering.
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