It may seem time-consuming, but with big paintings it saves a lot of work in the long run.
|My watercolor sketch. It's gridded on a piece of plexiglass laid over the drawing.|
|I drew the mast positions in with charcoal and a straight-edge before starting to paint. That way their angle will match my sketch.|
That meant gridding up a second version. This time I decided to go with the original aspect ratio of the sketch, rather than cropping it. I liked the yawl I’d truncated the first time around.
|Straight lines, curves--it doesn't matter. Just find the point at which they intersect the grid, mark those points, and work from there. I usually do this in monochrome but since I was working from a watercolor sketch, I just massed color.|
I have a projector, but I find that gridding is more accurate and takes less time. Knowing how to do it is imperative for large projects, but it can be surprisingly useful in small paintings, too. Whenever you have trouble going from your thumbnail to the canvas, gridding is your go-to answer.
|Boats v.2, laid out 24X36 in just a few hours. Later today I can actually paint them.|
I realize many artists are math-phobic, but there are times when a bit of arithmetic can save you a world of pain.
First, work out whether the aspect ratio of your sketch is the same as the canvas. This is the proportional relationship between height and width. Sometimes this is very obvious, such as a 9X12 sketch being the same aspect ratio as an 18X24 canvas. But sometimes, you're starting with a peculiar little sketch drawn on the back of an envelope. You can use a trick you learned back in elementary school.
Remember learning that 1/2 was the same as 2/4? We want to force our sketch into a similar equivalent ratio with our canvas.
Let’s assume that you’ve cropped your sketch to be 8” across. You want to know how tall your crop should be to match your canvas.
Write out the ratios of height to width as above.
To make them equivalent, you cross-multiply the two fixed numbers, and divide by the other fixed number, as below:
The next step is to grid both the canvas and sketch equally. In my painting above, my grid was an inch square on the sketch and 4" square on the canvas, but as long as you end up with the same number of squares on both, the actual measurements don't matter. You can just keep dividing the squares until you get a grid that's small enough to be useful. For a small painting, that could be as simple as quartering the sketch and the canvas. I use a T-square and charcoal, and I’m not crazy about the lines being perfect; I adjust constantly as I go.
The last step is to transfer the little drawing, square by square to the larger canvas. I generally do this in a dark neutral of burnt sienna and ultramarine. On Friday, however, since I’d already done a grisaille and a watercolor sketch of the subject, I just transferred large blocks of color. It may seem time-consuming, but with big paintings it saves a lot of work in the long run.