Moth: a gouache and ink drawing

Working on a new illustration for an upcoming essay, I've learned a bit more about how to use gouache in my process.

Specifically, the problem I'm trying to solve is dark backgrounds. My work-in-progress essay takes place mostly at night, and the illustrations need to be very low-key — mostly dark tones with just a few highlights. This means I need to work dark-to-light instead of light-to-dark.

Working light-to-dark (as I usually do), I start with the white paper and apply dilute gray ink to render shadows. Layer by layer, I add successively darker tones while ‘saving’ the lightest areas until I have the range I need for my darkest shadows and brightest highlights.

Working dark-to-light, on the other hand, I need to start with black and add successively lighter gray and white tones until I have the full range I need. Gouache, being opaque, allows me to apply white paint over a black wash and, for the most part, the white will show up nice and bright.

Last time, I tried painting a moonflower and learned a lot about how to layer gouache and ink. I was working with a limited color palette (black, green, gold, and white) and I ran into a problem when I scanned the finished drawing. It was really hard to build masks from the scan.

When I work in black ink, I can scan the drawing and the resulting black-and-white image translates to a digital alpha channel really well. I can invert the image, then select Rasterize to mask in my photo editor, and the dark areas of my image become opaque while the light areas become transparent. In a sense, this allows me to ‘lift’ the ink off the paper.

If I apply the mask to a fill layer, I can make my drawing any color I want. I can change the color of the line-work itself, or I can add color fills ‘underneath’ the mask (on lower layers) which will show through the transparent areas. This gives me a lot of control over color and tone. And, being non-destructive, it also gives me a lot of latitude to experiment and fine-tune.

With a full-color painting, however, my post-processing is mostly constrained to the original colors. Once it’s scanned, I can’t easily convert the drawing to a mask, or significantly alter the color palette. If I try to push it past a certain point, my layers menu turns into incomprehensible spaghetti and the drawing itself quickly devolves into a muddy mess. Someone with more advanced Photoshop skills could probably do better, but this is the limits of my own kung fu.

My moon flower experiments made me realize that, most of the time, I prefer to handle color in the computer rather than on the paper. The computer is both forgiving and precise; it lets me change my mind and try different things so much more easily.

So, a possibly better approach occurred to me: I could use gouache as before, but work only in grayscale. Then, when I scan it in, I can use my masking technique to add color digitally. Likewise, if I stuck to grayscale, it might be easier to layer in black ink for line-work and detail.

Let’s give it a try.

Pencils, gouache, and ink

I shot a photo of a tiny moth, perched on a grass blade, in my back yard one evening. I decided to draw it: it’s a beautiful moth and I find them fascinating. I’m not sure, yet, if my essay with cover moths specifically, but at the very least maybe this drawing could serve as ‘B-roll’ — a quick detail that adds atmosphere.

A photo of a moth perched on a grass blade in my back yard.

I did my pencils on my iPad using Procreate, my favorite drawing app. For the most part, these days, I prefer to do pencils digitally. It’s easier to change things as I go and, subsequently, it’s easier to get the composition and proportions right. Also, digital pencils are separate from the ink or paint I apply later, so if I really mess up, I can just print another copy of the pencils and try again.

Once the pencils were done (I kept them pretty quick and rough), I printed them out in non-photo-blue lines(Note: Cyan lines are easier to ‘erase’ digitally after scanning. In some cases, they’ll simply disappear once the image is converted to grayscale. Read more about how that works here.)onto hot-press watercolor paper.

A pencil sketch of a moth, perched on a grass blade

Then I painted over my pencils in layers of gouache and ink. I forgot to take photos of the in-progress drawing, but here’s a summary:

  1. First I laid down a wash of mid-tone gray gouache, fairly dilute.
  2. This covered some of my original pencil lines, so I reinforced a few with a regular HB pencil.
  3. I painted a layer of black, fairly thick, over the gray wash, excluding the grass blades and the moth itself. My hope was that this would add more texture, allowing the looser brush strokes of the gray layer to show through on the primary elements.
  4. I used titanium white gouache, with a smaller brush, for highlight details on the moth’s wings and the grass blades. This turned out quite lovely over the gray paint.
  5. Finally, I used black pigment ink to add detail and line-work.
A gouache and ink painting of a moth on watercolor paper. The paper sits on a desk with brushes, ink bottles, and a paint tube alongside.


After the paint dried, I scanned it in and cleaned up the inevitable dust, smudges, and stray marks. Then I converted the image to grayscale and adjusted contrast a little.

The scanned moth drawing, in grayscale

Okay, now I needed to make masks. First, I made a ‘positive’ mask: I converted the whole drawing to an alpha channel as usual, so that the light areas become transparent, the dark areas become opaque, and gray areas become translucent. It works just like ink on paper.

A transparent mask taken from my moth drawing

But I had a problem. If I want this image to work over a dark background, I also need a mask that covers the whole drawing. Otherwise, the light areas (the butterfly, the grass blades, etc.) will just disappear.

At this point, I realized I’d made two mistakes. First, I shouldn’t have used a mid-tone as my base layer. Gray is translucent in an alpha channel, so I had no easy way of converting the drawing’s base layer to an opaque mask. Second, I hadn’t thought to scan the painting after finishing each layer. A scan of just the gray wash, or the black, would have made it easier to manipulate the layers digitally.

So, I ended up having to make an ‘outline’ mask by hand: by very carefully tracing edges of the paint strokes with a tiny brush in Affinity Photo. It was super tedious, but I was eventually able to make a pretty accurate outline that I could use to control the composite’s background color.

A masked outline of my moth drawing

After I finished the masks, I layered both together over a dark background. My ‘positive’ mask was applied to a black fill layer, and my ‘outline’ mask was applied to a white fill layer. The result is my drawing, but ‘lifted’ off the paper so that it works over any background color (like the dark gray shown here).

A first composite of my moth drawing, with both masks layered together

Okay, time to fine-tune some things. First, those grass blades and ‘overspray’ strokes feel distracting against the dark background. We’re losing the butterfly. I added a gradient overlay to the ‘positive’ layer, so the edges of the drawing get darker. This helps bring butterfly ‘forward’ and forces the background elements to recede a bit more. I also shifted the color of the ‘outline’ mask layer to a slightly darker gray, which darkened all the light tones.

Next, I reinforced the shadows with a darker gray, adding a bit more contrast. Finally, I added another fill layer, just below the butterfly, with bright white. The brightened the butterfly relative to the rest of the drawing, helping it stand out.

Then, I put down some more brush strokes (using my iPad again), in whites and grays, to add some finer grass blades, fuzzy textures, and out-of-focus bits to the background.

My moth drawing, with more details added to the background

Now it was finally time to think about color. After some experimenting and thinking it over, I decided I wanted to keep color very subtle. Human eyes don’t perceive color well in the dark; the less available light, the more ‘gray’ our vision becomes. I wanted the colors to be mainly atmospheric — so they just barely register in a way that you feel more than see.

I used a gradient map to add just a little color character — mostly cool tones — to the range of values. I leaned on turquoise and cobalt, in very low saturation, to try and create the effect of a flashlight beam on a summer night.

Moth: a gouache and ink drawing
A UI window showing the gradient map I used in my moth drawing


I like where this piece is going — I’m making some progress on how to work from dark to light, and how to use gouache alongside ink and digital media. This piece is feeling more confident and expressive than my moon flower experiments. Working in grayscale (and handling color digitally) is helping to reduce the number of decisions I have to make early in the process, and it means that early mistakes have less drastic consequences later.

This particular piece doesn’t feel quite right yet, though. I should have started from a black base coat rather than a mid-tone gray. That would make masking easier, for one thing. And, more importantly, it would have helped me see the image, from the beginning, as emerging from the dark. When I started with a base gray, I still, unconsciously, saw the drawing in terms of white. To that extent, the original drawing (on white paper) feels more natural and coherent to me than the finished composite over the dark cobalt.

But I think I’m getting a process down, and it’s starting to work. For the next piece, I’ll start from a black wash, make scans of each layer, and think a bit more about color treatments. Then we’ll see where that goes.