Graded wash: dissolving ultramarine into cerulean
A graded wash is not one wash, it is two washes sharing a wet seam. Get the seam wrong and you get a hard band across the middle of the sky that no amount of glazing will hide. This is the version that survives a 300 gsm rough sheet.
Ultramarine — Deep, warm-leaning blue. Granulates visibly.
| Pigment | Parts | Hex |
|---|---|---|
| French Ultramarine | 4 : 7 (57%) | #2E4A7D |
| Cerulean Blue Chromium | 2 : 7 (29%) | #4E93B8 |
| Burnt Umber | 1 : 7 (14%) | #6B4A34 |
- Mix two separate puddles, not one: a 4 : 0 strong ultramarine and a 0 : 2 cerulean. Never mix the gradient in the well.
- Wet the full band with clean water and let it go matte — about 40 seconds on rough 300 gsm.
- Lay the ultramarine end first with a 20 mm flat, three horizontal passes, keeping the bead alive.
- Rinse the brush, load cerulean, and start each new band by touching into the previous bead so the two puddles marry.
- Add a single brush-tip of burnt umber at the darkest corner; it stops the ultramarine from reading as a flat poster blue.
- Tilt the board 5 degrees toward the light end for the last two bands, then level it while the surface is still wet.
- Dry bone dry before judging — ultramarine lifts in value by roughly a full step as it dries.
Two puddles, one gradient
The most common failure is mixing the gradient on the palette until it looks right, then laying it down. That works on paper only until the mix begins to separate: ultramarine is a heavy, coarse particle and cerulean is a finer, slightly opaque one, so any pre-blend will stratify within a minute and leave a grey smear where you wanted blue.
Mix the ends strong and let the paper do the interpolation. Ultramarine at 4 parts to cerulean at 2 parts, both diluted to about the value of skimmed milk, is the starting ratio that holds.
Wetting the band first
Rough 300 gsm has a deep tooth. A dry start leaves pinpricks of unpainted white in the pits of the paper that only show once the sheet is dry. Wetting the band first with clean water and waiting for the sheen to disappear fixes this, but you lose the crisp bleeding edge you would get on cold press.
Forty seconds is the useful interval at 21 C and 50% humidity. In a dry studio it is closer to twenty; use a spray bottle to keep the band alive rather than re-wetting with a brush, which disturbs the sizing.
Why the burnt umber is not optional
Pure ultramarine dries to a violet-leaning blue that sits flat against white paper — a poster blue. A single brush-tip of burnt umber in the darkest corner drops the chroma just enough to read as distance. It is one to two percent of the total mix, and more than that turns the corner brown.
If you are painting a sky, that dark corner belongs at the top, because the deepest blue in a real sky is at the zenith, not at the horizon.
What matters
- Mix the two ends separately; pre-blending the gradient stratifies within a minute.
- Wet the band first on rough stock to avoid white pinpricks in the tooth.
- One brush-tip of burnt umber in the darkest corner kills the poster-blue look.
- Ultramarine lightens by about one value step as it dries — judge dry.
Handling note — Technique notes only. Pigment handling and studio ventilation requirements vary by product; follow the manufacturer's safety data sheet.