A flat wash that actually dries flat
A flat wash is the first skill that separates a watercolour that reads as professional from one that reads as muddy. On 200 gsm cold press the paper gives you roughly ninety seconds of working time before the sizing starts to lock the pigment down. Everything below assumes that window.
Cerulean — Heavy, coarse particle, strong granulation.
| Pigment | Parts | Hex |
|---|---|---|
| Cerulean Blue Chromium | 3 : 5 (60%) | #4E93B8 |
| Ultramarine Light | 1 : 5 (20%) | #5B74A8 |
| Ox Gall (medium) | 1 : 5 (20%) | #E8DFCB |
- Tape 200 gsm cold press to a board on all four sides; the sheet will cockel when it dries and the tape is what keeps the edge clean.
- Mix a puddle about the size of a 10 cm circle: 3 parts cerulean to 1 part ultramarine, water until the puddle looks like weak tea.
- Charge a 25 mm squirrel mop fully, touch the ferrule to the rim of the well once to shed the drip, then begin at the top-left corner.
- Pull a single band left to right at a shallow 15-degree angle, never lifting the brush mid-stroke.
- Reload and start the next band at the bottom of the previous one, picking up the bead of water that has run down.
- Keep the board flat. If the bead stalls, add one drop of ox-gall water with a pipette rather than more paint.
- Leave the wash undisturbed until it has lost its sheen — roughly 12 minutes in a 21 C room at 50% humidity.
- Dry flat, then lift the tape at a 45-degree angle away from the paper.
Why 200 gsm and not 300
Cold press 200 gsm absorbs a 25 mm mop load without buckling badly if it is taped down, and it dries in twelve to fifteen minutes. A 300 gsm sheet holds more water and gives you longer to fix a stall, but it also holds the bead higher, so a mistake at the bottom edge floods further.
The trade is simple: 200 gsm punishes hesitation, 300 gsm punishes overloading. Start on 200 gsm because it forces you to load the brush correctly instead of relying on the sheet to absorb the error.
The colour choice is doing half the work
Cerulean is a heavy, slightly granular pigment. In a flat wash that granulation settles into the tooth of cold press and gives the panel a faint speckle that reads as texture rather than dirt. Adding one part ultramarine deepens the value without turning the mix grey, because both pigments are already on the cool side of neutral.
Do not substitute phthalo blue for cerulean here. Phthalo is roughly eight times stronger by weight and will produce a wash that looks like stained glass under the same dilution.
Reading the bead
The bead is the thin line of pooled water at the bottom of the last stroke. It should be the width of a fingernail. If it widens to a finger, you loaded too much; if it disappears entirely, the paper is drinking faster than you can lay paint and the next band will show a hard start mark.
A stalled bead is almost always a sizing problem, not a paint problem, which is why the fix is ox gall rather than more pigment.
What matters
- 3 : 1 cerulean to ultramarine, diluted to weak-tea strength, keeps the wash luminous.
- Tape all four edges on 200 gsm or the sheet will cockle and pool at the centre.
- Keep the board flat; tilt only when you deliberately want a graded edge.
- A stalled bead means sizing, not strength — add ox gall, never more paint.
Handling note — Technique notes only. Pigment handling, dust and solvent safety vary by product — read the manufacturer's safety data sheet before studio use.