Acrylic Mediums: What They Are and How to Use Them

Most painters squeeze paint straight from the tube and wonder why their results feel limited. Acrylic mediums are what change that.

These acrylic polymer emulsion-based additives modify how paint behaves: its viscosity, transparency, drying time, surface finish, and texture. No pigment added. Just control.

Whether you’re after thick impasto peaks, smooth glazing layers, or fluid paint that flows without cracking, there’s a medium built for it.

This guide covers everything from gel mediums and pouring mediums to the GAC series and slow-drying open mediums, so you can match the right product to your acrylic painting technique instead of guessing.

What Are Acrylic Mediums

Acrylic mediums are acrylic polymer emulsion-based additives that you mix directly into acrylic paint to change how it behaves, not what color it is. They modify viscosity, transparency, drying time, surface finish, and texture without adding pigment.

Think of them as the paint without the color. Golden Artist Colors describes gel mediums as “colorless paints” made from the same 100% acrylic polymer binder used in the paint itself.

Mediums vs. Additives vs. Varnishes

People mix these three up constantly. They’re not the same thing.

Why Artists Use Them

Straight from the tube, acrylic paint is already a finished product. Mediums expand what that paint can do.

The acrylic medium market was valued at USD 1.2 billion in 2024 and is projected to reach USD 1.8 billion by 2033 (Verified Market Reports), which reflects just how central these products have become to acrylic painting techniques across both studio and hobby contexts.

Acrylic paints account for roughly 32% of global art paint unit volumes in 2024 (Industry Research). Mediums are a core part of that ecosystem, not an optional extra.

How Acrylic Mediums Change Paint Behavior

Every medium targets one or more of five core properties: consistency, transparency, drying time, surface finish, and texture. Understanding which property you need to change is how you pick the right product.

Consistency and Viscosity

Thickening: Gel mediums increase paint body, letting it hold peaks and brushstroke marks.

Thinning: Fluid and glazing mediums reduce viscosity without breaking down the acrylic binder. This is the key difference from just adding water.

Water weakens the acrylic polymer emulsion when added beyond roughly 30% of the paint volume. Fluid mediums thin the paint while keeping the binder intact, which protects paint film integrity over time.

Transparency and Finish

Glazing mediums increase transparency, which is what makes glazing in acrylic painting work as a layering technique. Each thin, transparent layer lets the color beneath show through, building up depth gradually.

Finish is separate from transparency. A gloss gel and a matte gel can have identical viscosity but dry with completely different sheens.

Mixing Ratios Matter

There’s no universal ratio. Results shift depending on the medium type, the paint brand, and the surface.

The general principle: the more medium you add, the more pronounced the effect. But going past recommended ratios, especially with retarders, can affect how the paint film cures. A retarder added beyond about 15–20% of paint volume starts to compromise the film.

Gel Mediums

Gel mediums are the most widely used category. In 2023, gel acrylic medium held 38% of total acrylic medium market share, the largest of any type (Verified Market Reports). That’s not surprising given how many problems they solve at once.

They are essentially high-viscosity acrylic polymer with no pigment. The same binder as the paint, just without any color.

Soft Gel vs. Regular Gel vs. Heavy Gel

Soft gel: Similar viscosity to heavy body paint. Good for extending paint, creating thin impasto, and collage adhesion where you want some transparency.

Regular gel: Stiffer. Holds moderate peaks, bridges the gap between soft and heavy.

Heavy gel / Extra heavy gel: Very stiff. Holds sharp, distinct peaks and palette knife textures. Golden’s Extra Heavy Gel is a go-to for thick impasto work where the artist wants the marks to stay exactly as placed.

Matte vs. Gloss Gel

Consistency stays the same across finish types within the same weight. A Heavy Gel Gloss and a Heavy Gel Matte feel identical in the jar and handle the same way. The difference only appears once the paint dries.

Gloss versions produce more saturated color. Matte versions contain fine silica particles that scatter light, which also slightly reduces transparency. Worth knowing before you choose matte for a glazing layer.

Using Gel for Collage and Texture

Soft gel gloss is the standard choice for collage work, as an adhesive and a sealing layer. It bonds paper, fabric, and found materials to canvas reliably.

For texture, artists mix gels with sand, sawdust, eggshells, and similar materials to create custom surfaces. Ready-made versions, like pumice gel, glass bead gel, and mica flake gel, are also available from brands like Golden Artist Colors and Liquitex.

Gel mediums are also what makes impasto in acrylic painting structurally sound. Without a gel extender, thick paint alone risks cracking as it dries and shrinks.

Fluid Mediums and Glazing Mediums

Fluid mediums reduce paint viscosity to create washes, thin pours, and transparent layers. They’re what you reach for when you want the paint to flow rather than sit.

How Fluid Mediums Differ from Water

Adding water to acrylic paint thins it, but past about 30%, it starts to break down the acrylic binder. The dried paint can become brittle, crack, or lose adhesion to the surface.

Fluid mediums thin the paint without that risk. They’re the same polymer base, just at lower viscosity, so the binder ratio stays stable no matter how much you add.

Most professional portrait and botanical artists I’ve seen work stick to fluid mediums over water for any wash that needs to stay stable across multiple layers. With watercolor-style layering on absorbent ground, this matters a lot.

Glazing Medium Specifically

What it does differently:

• Increases transparency more than a standard fluid medium
• Slightly extends open working time (not dramatically, but noticeably)
• Produces a glassy, smooth layer with minimal brushstroke texture
• Builds color depth through transparent layers without muddying the paint below

Glazing as a technique goes back centuries in oil painting. In acrylics, glazing medium makes it practical without requiring days of drying time between layers. This connects directly to oil painting glazing techniques, where the same color-depth principle applies but over much longer sessions.

Liquitex and Winsor & Newton both make dedicated glazing mediums. Golden’s equivalent is their Clear Leveling Gel at thin dilution, though it behaves slightly differently due to its long-rheology formula.

Pouring Mediums

Pouring mediums are designed for one specific job: making acrylic paint flow across a surface in a controlled way without cracking, crazing, or losing adhesion when it dries.

Fluid acrylic pouring methods have grown significantly in the arts and crafts market. The global arts and crafts market is projected to reach USD 67.39 billion by 2030 at a CAGR of 7.4% (The Business Research Company), with acrylic pouring techniques driving a substantial portion of that growth in the painting and drawing segment.

What Pouring Mediums Actually Do

They reduce surface tension in the paint so it spreads and self-levels without separating into puddles.

Key property: When the paint dries, it forms a flexible, crack-resistant film. That’s the main technical difference from just thinning with water or using a generic fluid medium for pouring.

Golden’s GAC 800 is the professional benchmark here. It’s specifically formulated to prevent crazing (the spiderweb cracking that happens when paint dries too fast or the film is too rigid). DecoArt Pouring Medium and Liquitex Pouring Effects Medium are the most common options at the mid-market level.

Pouring Techniques and Medium Choice

Different pour techniques need slightly different medium viscosities.

Floetrol is a popular substitute among hobbyists. It’s a paint conditioner originally made for house paint, not artist acrylics, and it works reasonably well for casual pouring. For work you want to last, a purpose-made pouring medium like GAC 800 or Liquitex is worth the difference in cost.

A lot of people getting into acrylic pouring for the first time underestimate how much the medium-to-paint ratio affects cell formation. Too much medium and the cells disappear. Too little and the paint won’t flow evenly. It takes a few test pours to find the right balance for your specific paints.

Texture Mediums and Pastes

Texture mediums add physical material to the paint surface. They’re not about changing how paint flows. They change what the surface actually feels and looks like when dry.

Modeling Paste vs. Light Modeling Paste

These two are the most common and most confused.

Modeling paste: Heavy, opaque, dries very hard. Good for rigid surface textures, building up relief elements, and palette knife work where you want the marks to hold exactly as placed. The tradeoff is inflexibility. On a surface that moves (like an unstretched canvas), thick applications can crack.

Light modeling paste: Less dense, more flexible when dry. Made with hollow microspheres that reduce weight while keeping the paste workable. Safer for flexible supports and thicker builds.

Golden Artist Colors publishes clear guidance on which paste to use at what thickness. For layers over 3–4mm, light modeling paste is the practical choice on canvas.

Specialty Texture Options

Beyond modeling paste, there’s a whole range of texture gels built around specific materials.

• Pumice gel (coarse and fine): Gritty, stone-like surface. Works well for landscape work or mixed media backgrounds
• Glass bead gel: Smooth, reflective texture with tiny glass spheres embedded in the dried surface
• Natural sand texture gel: Similar grit to pumice but with a warmer, earthier look
• Fiber paste: Creates a soft, paper-like surface that accepts dry media (charcoal, pastel) well

Liquitex Natural Sand Texture Gel and Golden Coarse Pumice Gel are the most available options in most art supply stores. Both mix cleanly with acrylic paint and accept additional paint layers once dry.

Texture mediums connect naturally to acrylic paint texture ideas and palette knife techniques. The paste does the structural work; the paint adds color on top. That separation actually gives you more control over the final result than trying to build texture and color simultaneously.

Slow-Drying and Open Mediums

Standard acrylics dry fast. On a hot, dry day, heavy body paint can become unmovable in under 10 minutes on canvas. For blending-heavy work, portrait painting, or wet-on-wet techniques, that’s a real problem.

Retarders and open mediums both address this, but they work differently and they’re not interchangeable.

Retarder vs. Open Medium

Retarder: An additive that slows water evaporation. It extends working time but does not change the paint system itself. Must be used in small amounts (typically under 15–20% by volume). Exceeding that ratio can prevent the paint film from curing properly.

Open medium: A purpose-formulated medium designed for use with Golden’s OPEN Acrylic system. It can be added in any ratio without compromising film integrity, unlike a retarder additive.

In lab tests conducted by Golden Artist Colors, standard Heavy Body Acrylics become unmovable at around 30 minutes. OPEN Acrylics stay workable for 1 to 3 hours in thin applications and can be fully reactivated for up to 12 hours after initial application.

GOLDEN Open Medium and the Open System

OPEN Acrylics are slow-drying by design, staying wet on the palette for extended periods without skinning over. The OPEN Medium, Gel, and Thinner are formulated specifically for this system.

• OPEN Medium and Gel can be added in any ratio to OPEN Acrylics
• OPEN Thinner should not exceed a 3:1 paint-to-thinner ratio (Golden’s guidance)
• Thick applications require a minimum of 30 days before varnishing

Mixing OPEN Acrylics with standard Golden acrylics proportionally adjusts drying time. This is how most artists use the system, not as a full replacement but as a tool for specific passages where blending matters most.

Who Benefits Most

Portrait painters coming from oils have found OPEN Acrylics one of the few acrylic systems that allows genuine wet-in-wet technique without fighting the clock on every brushstroke.

Plein air painters working in warm, dry conditions also get real value from extended open time. The tradeoff is that thick OPEN layers can remain tacky for days, which makes them impractical for layered impasto work where you need the surface stable.

For blending in acrylic painting, this is currently the most reliable acrylic system available without switching to oils or water-miscible oil paints.

Specialty Mediums

Beyond gels, fluid mediums, and texture pastes, there’s a category of mediums built for very specific jobs. Most artists don’t need all of them. But when you do need one, nothing else substitutes cleanly.

The GAC Series

Golden Artist Colors’ GAC series is the most comprehensive line of specialty acrylic polymers available to artists. Each GAC is a distinct polymer formulation, not just a variation in thickness.

GAC polymers are thinner than standard Golden mediums and should never be shaken, only gently stirred, as shaking incorporates foam that creates a hazy film when dry.

Crackle Paste and Fiber Paste

Crackle paste dries with intentional surface cracks. The crack size depends on application thickness: thicker layers produce wider, more dramatic cracks. Good for aged surface effects in mixed media and decorative work.

Fiber paste produces a soft, absorbent surface that accepts dry media like charcoal, pastel, and graphite directly over it. Tri-Art and Golden both make versions. It’s one of the few acrylic mediums that genuinely bridges acrylic and dry media in a single surface.

Absorbent Ground and Clear Gesso

These are grounds, not mediums in the traditional sense, but they function as surface modifiers in ways that affect the entire painting process above them.

Absorbent ground creates a watercolor-like surface on canvas or board, allowing watercolor-style paint handling with acrylics. Golden’s version is widely used by artists who want the optical quality of watercolor but the permanence of acrylic.

Clear gesso primes a surface without adding the white opacity of traditional gesso, which is useful when painting on dark or toned supports where you want the ground color to remain visible. It’s a practical alternative to standard gesso for layering in acrylic underpainting over colored grounds.

Mixing Acrylic Mediums Together

Most acrylic mediums can be combined with each other. They share the same polymer base, so compatibility within a brand’s range is generally not a concern.

Liquitex’s chemists test every product in the range in 50:50 combinations to confirm compatibility before release. The result is that their full range, from Heavy Body to Acrylic Ink to Spray Paint, is designed to work together without adhesion problems or film instability.

What Works and What Doesn’t

Daler-Rowney’s technical guidance makes the boundary clear: acrylic mediums mix well with other acrylics, but should not be combined directly with oil mediums (different drying chemistry) or watercolor additives (binder and pH differences).

Safe to combine:

• Gloss gel + matte medium (creates a satin finish)
• Pouring medium + soft gel (flow with controlled body)
• Fluid medium + retarder (extended workability in thin layers)

Avoid: layering matte finish over gloss finish without testing adhesion first, since the silica particles in matte products can reduce bonding between layers.

Testing Before Committing

Making small test swatches is not optional for multi-medium work. It’s the one thing that separates a frustrating result from a reliable one.

Observe drying time, adhesion, finish, and flexibility across several days, not just after the initial surface dry. Some combinations appear fine at first and show problems later, particularly with thick builds where volatile materials take longer to leave the film.

This matters especially in layering acrylic paint, where incompatible finish combinations between layers can cause adhesion failure when the work is handled or stored under pressure.

Choosing the Right Acrylic Medium

The acrylic medium market is projected to grow from USD 1.2 billion in 2024 to USD 1.8 billion by 2033 (Verified Market Reports). Part of that growth is driven by new artists entering the hobby and struggling with exactly this decision. There are a lot of products and most of them look similar in the jar.

A decision framework helps more than a product list.

Decision by Desired Result

Budget Considerations

Student-grade mediums from brands like Liquitex Basics work fine for most applications. The difference at the professional level (Golden, Liquitex Professional) is primarily in consistency, polymer quality, and archival longevity, not in immediate visual results.

For casual or hobby use, the Basics range from Liquitex covers most needs at a lower cost. For work you want to preserve long-term or sell, professional-grade mediums are worth the price difference.

The global art supplies market was valued at USD 12.2 billion in 2023 and is projected to reach USD 20 billion by 2035 (Allied Market Research), with professional-grade products driving a disproportionate share of revenue relative to volume. Hobbyists buy more units; professionals spend more per unit.

When to Skip Mediums Entirely

Not every painting needs a medium. Straight heavy body paint from a brand like Golden or Liquitex Professional already has excellent paint film integrity, good working consistency, and strong adhesion.

Mediums add value when you need something the paint alone can’t do: more transparency, more texture, more flow, or more time. If the paint does what you need as it is, adding a medium just introduces another variable.

For beginners getting into acrylic painting materials for the first time, the most practical starting point is soft gel gloss (for collage and extending), a fluid medium (for washes), and a glazing medium if you plan to layer color. That covers most techniques without needing a shelf full of specialty products.

FAQ on Acrylic Mediums

What is an acrylic medium?

An acrylic medium is an acrylic polymer emulsion-based additive mixed directly into paint to change how it behaves. It modifies viscosity, transparency, drying time, or surface finish without adding pigment. Same binder as the paint, no color.

What is the difference between a medium and a varnish?

Mediums are mixed into paint during the painting process. Varnishes are applied as a protective top coat after the painting is finished and fully dry. They serve different purposes and are not interchangeable.

Can I use water instead of an acrylic medium to thin paint?

You can, but only up to about 30% by volume. Beyond that, water breaks down the acrylic binder, weakening paint film integrity and risking adhesion failure over time. Fluid mediums thin paint safely at any ratio.

What is gel medium used for?

Gel medium thickens paint, builds impasto texture, extends paint volume, and works as a collage adhesive. It comes in soft, regular, and heavy weights, each holding different peak heights. Finish options include gloss, satin, and matte.

What does glazing medium do?

Glazing medium increases paint transparency and slightly extends open working time. It lets you build up thin, luminous color layers without muddying the paint below. It’s central to glazing technique in acrylic painting.

What is a pouring medium?

A pouring medium reduces surface tension so paint flows and self-levels across a surface without cracking or crazing when dry. Golden’s GAC 800 is the professional standard. DecoArt and Liquitex both offer mid-market options.

What is the difference between a retarder and an open medium?

A retarder is an additive that slows drying time but must stay under roughly 15–20% of paint volume. An open medium, like Golden’s OPEN system, can be added in any ratio without compromising the paint film.

Can I mix different acrylic mediums together?

Yes. Most acrylic mediums share the same polymer base and are compatible with each other. Liquitex tests all products in 50:50 combinations before release. Avoid mixing acrylic mediums directly with oil or watercolor-based mediums.

What is modeling paste used for in acrylic painting?

Modeling paste builds rigid, opaque surface texture. It dries hard and holds fine detail well. For flexible supports like canvas, light modeling paste is safer for thick builds, as standard modeling paste can crack on surfaces that flex.

Do I need acrylic mediums as a beginner?

Not immediately. Start with soft gel gloss for collage work, a fluid medium for washes, and a glazing medium if you plan to layer color. Those three cover most techniques without overcomplicating your acrylic painting materials setup.

Conclusion

This conclusion is for an article presenting acrylic mediums as practical tools, not optional extras.

Gel mediums, pouring mediums, glazing mediums, texture pastes, and the GAC series each solve a specific problem. Knowing which one fits your technique saves time, material, and frustration.

Paint consistency, surface finish, and paint film integrity all shift depending on what you add and how much. The ratios matter.

Start with two or three mediums that match how you already work. Test on small swatches before committing to a full painting.

Golden Artist Colors, Liquitex, and Winsor & Newton all publish detailed technical guidance. Use it. The more you understand acrylic polymer emulsion chemistry, the more predictable your results become.