How to create gouache–acrylic hybrid studies that withstand varnishing using absorbent ground and artist-grade fixatives

I love pushing the limits of materials — the meeting point between gouache’s matte, velvety presence and acrylic’s resilience is one of my favourite playgrounds. Over the years I’ve developed a workflow for creating small hybrid studies that retain gouache’s delicate surface but can safely be varnished or handled without the gouache lifting or changing tone. The keys are an appropriately absorbent ground, gentle layering, and the right fixatives. Below I share the practical steps, materials I trust, common pitfalls and a few tests you can run at home.

Why combine gouache and acrylic?

Gouache brings a softness and immediacy — it’s brilliant for quick studies, soft edges and layered opacities. Acrylic offers permanence, flexibility and the ability to varnish. When I want the best of both worlds (the subtle reworkability of gouache with the protection of acrylic varnish), hybrid studies are my solution. But gouache is water-soluble and reactivates easily, so protecting those surfaces requires thought.

What makes a surface "safe" for varnishing?

There are two things I aim for before varnishing a gouache-containing piece:

Reduce the solubility of the gouache surface so it won’t lift when a varnish (often water-based or acrylic polymer) is applied.

Create a consolidated surface that accepts varnish evenly, avoiding patchiness or beading.

Both goals are helped by an absorbent ground and by using artist-grade fixatives rather than hobby sprays.

Materials I use (and why)

Support	Heavyweight watercolour paper (300gsm or heavier) or primed hardboard panels
Absorbent ground	Golden Absorbent Ground or Liquitex Absorbent Ground — these create a slightly porous, toothy surface that takes gouache well and prevents sitting-on-topiness
Acrylic	Artist-grade acrylics (Golden, Winsor & Newton Professional) for underpainting and final protective coats
Gouache	Artist-quality gouache (Schmincke Horadam, Winsor & Newton Designers) — they are more stable and finer in pigment than student brands
Fixatives	Rembrandt or Schmincke matt fixative (artist-grade spray), or a water-based acrylic isolation coat like Golden GAC 800 for greater protection
Varnish	Golden MSA Varnish (made for mixed-media) or Winsor & Newton Professional Acrylic Varnish — test first
Tools	Soft brushes, spray booth or well-ventilated area, glassine paper for testing

Preparing the support with absorbent ground

If you’re starting on heavy watercolour paper, I still recommend applying a thin layer of absorbent ground. It does two things: it evens out sizing inconsistencies and produces a surface that accepts both gouache and thin acrylic washes without beading. I usually do the following:

Apply one thin, even coat of Golden Absorbent Ground with a soft brush across the whole sheet or panel. Brush strokes should be minimised; use long, even strokes and smooth any ridges immediately.

Let it dry fully (often 1–2 hours, depending on humidity). Lightly sand with a very fine grit (400–600) if you want an extra-smooth surface for fine detail.

If you want more absorbency, add a second thin coat. Too many coats will reduce tooth and can lead to a more plastic surface — which is counterproductive.

Working sequence: acrylic underlayers, gouache passages, consolidation

My favourite sequence for longevity and flexibility is:

Begin with acrylic underpainting for structure. Thin washes of transparent acrylic (or acrylic ink) help me establish values and composition without disturbing the absorbent ground too much.

Apply gouache for mid-tones, local colour and soft edges. Because the absorbent ground draws water away slightly, gouache dries matt and non-beadingly rather than pooling.

If I need to add highlights or rework, I’ll use opaque gouache after any acrylic underlayers have cured (24 hours for most artist acrylics).

For final crisp marks, sometimes I use a small amount of acrylic over gouache — but only after a consolidation step (below).

Consolidating gouache: fixatives and isolation coats

This is the crucial stage. Never move straight from fresh gouache to a varnish. I perform one of the following tests to decide how protective I need to be:

Rub test: gently rub a corner of a dried gouache area with a fingertip. If pigment smudges, it needs consolidation.

Water droplet test: place a tiny drop of water; if the paint reactivates and blooms, consolidation is necessary.

Options for consolidation:

Artist-grade matte fixative spray: Rembrandt or Schmincke make fixatives that reduce solubility without drastically changing colour. Work in a ventilated space, apply two light even coats, allowing 15–30 minutes between each. Test first: some fixatives slightly darken colours.

Isolation coat with a water-based acrylic medium: Golden GAC 800 or an acrylic gloss medium thinned slightly with water can act as an isolation coat. This creates a non-water-soluble barrier you can varnish over. Apply thinly with a soft brush; two thin coats are safer than one heavy.

Hybrid approach: I sometimes use a light spray fixative first, then follow with a very thin isolation coat. This gives extra security when I plan to varnish flat or gloss.

Varnishing: what I do and the tests I run

Before varnishing the whole piece I always test on a corner or on a sacrificial sample. My varnishing routine:

Ensure all layers (acrylic, fixative/isolation coats) are fully dry — 24–72 hours depending on products and humidity.

Test-spray or brush a small area with the chosen varnish. Golden MSA is lovely because it’s removable and compatible with many mixed-media materials, but it’s solvent-based and needs a fume hood. Winsor & Newton acrylic varnish is water-based and practical for studio use.

If varnish beads or causes any reactivation, stop. That means either the fixative wasn’t adequate or it’s incompatible. Try a different isolation coat or allow more cure time.

Varnish in thin even layers. If using spray, keep the can 25–30 cm away and apply several light passes rather than one heavy coat.

Common pitfalls and how to avoid them

Using student-grade fixatives or sprays: They can yellow or be insufficiently consolidating. Invest in artist-grade products.

Skipping absorbent ground: Without it gouache can sit on top, remain overly soluble and bead when varnish is applied.

Applying heavy isolation coats: Thick acrylic layers can change the optical quality and flatten gouache’s matte charm. Thin, even coats are better.

Varnishing too soon: Patience is essential — allow curing time for acrylics and fixatives.

Quick test you can do at home

Cut a small piece of your support, apply absorbent ground, then do a mini study with acrylic and gouache. Let it dry, apply your chosen fixative, then test with a tiny drop of varnish. Record what you used and the results — build your own reference swatches for different product combinations.

These hybrid studies have become a regular part of my practice: they let me explore colour and composition quickly while still producing work that’s durable enough to show, sell or varnish for protection. With a considered ground, the right fixative and a spirit of testing, you can keep the best qualities of gouache while avoiding the worry that a varnish will ruin a lovely surface.