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When it comes to acrylic painting, the paint itself is only half the story. The real magic often lies in the mediums, those jars, tubs, and bottles you’ve probably seen on the shelves and wondered, what do they actually do?

Acrylic mediums are designed to alter the properties of paint, extend your techniques, and open new creative possibilities.

From preparing your surface to building dramatic textures or achieving delicate flows, mediums are an essential part of any artist’s toolkit. In this guide, we’ll walk through some of the most popular acrylic mediums, what they do, and how you can use them in your practice.

Gesso – The Foundation of Every Surface

Before the paint even hits your canvas, gesso does the heavy lifting. Acting as a primer, it prepares your surface by adding “tooth” for the paint to grip, ensuring your colours remain vibrant and your artwork stands the test of time.

White gesso provides a clean, bright surface and is the most commonly used.

Clear gesso allows the underlying surface, such as woodgrain or coloured paper, to show through while still giving you the necessary foundation.

Black gesso creates a dramatic base for moody works or to help bright colours pop with intensity.

Most artists apply one to two coats, depending on the surface's absorbency. While gesso is often associated with canvas, it’s equally valuable on wood, paper, and board.

Crackle Paste – Texture with Character

Crackle paste is a medium that naturally fractures as it dries, producing an aged, weathered effect. It’s often used to create vintage aesthetics, distressed backgrounds, or as a dramatic base layer for abstract works.

To get the best result, apply the paste in thicker sections for deep cracks, or thinner layers for subtle veining.

For maximum impact, use contrasting paint colours above and below the paste so the cracks stand out. Think of it as giving your work instant history and depth.

Sand Texture Medium – Adding Earthy Grit

As the name suggests, sand texture medium introduces a grainy, tactile quality to your paint. It’s a favourite for artists looking to mimic natural textures: think beach scenes, desert landscapes, or urban walls.

By mixing it with acrylic paint, you can create unique surfaces that play with light and shadow, giving dimension and authenticity to your work. For abstract painters, it’s also a brilliant way to incorporate unexpected tactile effects that draw viewers in.

Light Moulding Paste – Sculpt Without the Weight

Traditional moulding paste can add significant heft to your artwork, but light moulding paste offers the same sculptural possibilities without the weight. It’s airy, easy to spread, and dries to a strong but lightweight finish.

This medium is perfect for artists who want to carve into their surface, build layers, or create 3D effects without warping their canvas. Once dry, it can be painted over with acrylics, or sanded back for a smoother result.

Gel Medium – Versatile and Essential

If there’s one medium every acrylic artist should try, it’s gel medium. In many ways, it’s the Swiss Army knife of mediums.

It can extend paint without changing colour intensity.

It can alter transparency, allowing for glazing effects or subtle layering.

It also functions as an adhesive, making it ideal for collage and mixed media work.

Available in gloss, matte, or semi-gloss, gel mediums dry clear and can be built up for textural effects. They’re particularly valuable for artists experimenting across multiple surfaces and styles.

Flow Medium – Smooth and Controlled

Flow medium (sometimes called fluid medium) reduces the viscosity of acrylic paint, allowing it to spread more evenly without diluting the pigment strength the way water does.

This makes it ideal for fine detail, controlled line work, glazing, or large fluid applications like acrylic pouring. It keeps colours strong while giving the artist complete control over how the paint moves across the surface.

Why Use Mediums?

Mediums are not about complicating your process — they’re about expanding it. A single tube of acrylic paint can behave in dozens of different ways depending on the medium you combine it with. For artists, this means more freedom, more control, and more opportunities to create unique, professional results.

Whether you’re preparing a canvas with gesso, experimenting with sculptural forms in moulding paste, or creating delicate veils of colour with flow medium, these tools offer creative flexibility that can completely transform your practice.

FAQs: Acrylic Mediums Explained

What is an acrylic medium?
An acrylic medium is an additive mixed with acrylic paint to change its properties, like texture, drying time, or flow. Mediums let artists achieve effects that aren’t possible with paint alone.

Do I need to use acrylic mediums, or can I just paint?
You can absolutely paint without them, but mediums expand your options. They help you prepare surfaces, create textures, adjust transparency, or control flow for more professional results.

What does gesso do?
Gesso acts as a primer, sealing and preparing surfaces like canvas, wood, or paper. It creates the right level of absorbency and texture so your paint sticks properly and stays vibrant over time.

Can I use clear or black gesso instead of white?
Yes. Clear gesso keeps the natural look of the surface beneath, while black gesso provides a dramatic base that makes bright colours stand out. White gesso is the most common choice for a clean start.

What is crackle paste used for?
Crackle paste creates a fractured, weathered effect as it dries, making your artwork look aged or distressed. It’s especially effective for vintage styles, backgrounds, or layered abstract pieces.

How do texture mediums like sand paste work?
Sand texture medium adds a gritty, tactile quality to your paint. It’s perfect for natural textures such as beaches, stone, or desert landscapes, and gives your work an earthy, dimensional finish.

What’s the difference between regular and light moulding paste?
Regular moulding paste is dense and adds significant weight, while light moulding paste is airy and easier to spread. Both create 3D sculptural effects, but the light version prevents heavy build-up or canvas warping.

Why is gel medium so popular with acrylic painters?
Gel medium is versatile: it can extend paint, adjust gloss levels, increase transparency, and even work as an adhesive for collage. It’s a go-to product for both traditional painters and mixed media artists.

What does flow medium do?
Flow medium thins acrylic paint without weakening the colour pigment. It’s commonly used for smooth blending, detailed line work, glazing, or acrylic pouring where control and fluidity are essential.

Can I mix different acrylic mediums together?
Yes, many mediums can be combined to achieve custom results. For example, you can use gel medium with sand medium for textured glazes, or gesso under crackle paste for a stronger base.

Do acrylic mediums change drying time?
Some do. Gel and moulding pastes can slow drying and allow for more working time, while flow mediums often speed up application but keep pigment intensity intact. Always check the label.

Are acrylic mediums beginner-friendly?
Definitely. Start with gesso for priming, then try gel or flow medium to see how they change your paint. Most mediums are easy to use and designed to make experimenting fun and accessible.

At Art Shed, we believe every artist deserves access to the right tools, whether you’re experimenting for the first time or refining your professional technique.

Our range of acrylic mediums includes options for all styles, budgets, and creative goals.] Explore the full range of acrylic mediums here and find the perfect fit for your next project.