Flat wash on hot press: controlling a surface with no tooth
Hot press is the honest paper. Cold press forgives a slightly uneven load because the tooth scatters pigment; hot press shows every hesitation as a watermark. This is the routine that makes a 300 gsm hot press panel read as a single, deliberate colour field.
Cobalt — Mid-value, semi-opaque, violet-leaning.
| Pigment | Parts | Hex |
|---|---|---|
| Cobalt Blue | 4 : 6 (67%) | #3B6FA8 |
| Cobalt Turquoise | 1 : 6 (17%) | #4E9E9C |
| Quinacridone Rose | 1 : 6 (17%) | #C2537A |
- Hot press has no tooth to hide a mistake. Pre-stretch the sheet or accept that the tape line will be visible around the panel.
- Damp the sheet evenly with a spray bottle from 30 cm and blot once with a clean towel. Target: cool to the cheek, not glossy.
- Mix cobalt with a quarter-pipette of cobalt turquoise. The turquoise is a mixer here, not a colour — it stops cobalt drying chalky.
- Lay the wash with a 30 mm wash brush in four overlapping vertical bands, going top to bottom so gravity works with you.
- Never go back into a band that has lost its sheen. On hot press the sizing seals in about 25 seconds.
- Add the rose only at the final band, half a brush-tip, to warm the bottom edge by one or two degrees of hue.
- Dry flat under a sheet of clean newsprint to slow the drying rate and avoid a tide line at the border.
Pre-wetting is not optional
A dry hot press sheet grabs the first pigment it touches and holds it, so the opening stroke is always darker than the second. Damping the sheet uniformly with a spray bottle equalises absorption and gives you a two-second grace period on each band.
The dampness level matters more than most tutorials admit. Glossy means too wet and the pigment will flood outward; cool and matte means correct. Test on the back of your hand — if it feels cool but the towel comes away nearly dry, you are on target.
Cobalt turquoise as an anti-chalk agent
Cobalt blue dries with a slightly milky film because of its relatively large particle size. One part cobalt turquoise in four parts cobalt blue does not change the hue meaningfully, but it interferes with that film and keeps the wash luminous.
The same trick works in reverse with rose: cobalt blue and quinacridone rose in a 4 : 1 ratio produce a clean violet. Push it past 2 : 1 and the mixture turns muddy, because cobalt is semi-opaque and starts to flatten the rose.
The twenty-five second rule
On 300 gsm hot press at 21 C, the sizing closes roughly twenty-five seconds after you lay the paint. After that, any brush you touch to the surface will lift pigment and leave a lighter streak that cannot be glazed back to an even tone.
This is why the entire routine is planned around never re-entering: four bands, four loads of the brush, one continuous rhythm. Count them out loud if it helps.
What matters
- Damp the sheet evenly first — a dry hot press start always shows a dark opening stroke.
- Four parts cobalt blue to one part cobalt turquoise keeps the wash from drying chalky.
- The sizing closes about 25 seconds after you lay paint; plan the band count before you start.
- Dry under newsprint to slow the rate and prevent a tide line at the tape.
Handling note — Technique notes only. Cobalt pigments are heavy-metal compounds — follow the manufacturer's safety data sheet and never sand a dry cobalt wash without respiratory protection.