Introduction To Acrylic Mediums
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The most common mistake beginners make is thinning acrylic paint with too much water.
The Breaking Point: If you add more than 30% water, you spread the glue molecules too far apart. They cannot link together.
The Result: The paint film becomes weak ("underbound"). It may chalk, flake off, or lift up when you paint a second layer over it.
The Solution: Use mediums. They are essentially "colorless acrylic paint". You can add as much medium as you want without ever weakening the chemical bond.
Texture Modifiers (Gels)
These change the body of the paint. They make it thicker or harder.
1. Gel Mediums (Soft, Regular, Heavy, Extra Heavy)
What it is: Tubbed white goo that dries clear.
Use: As an extender: Mix it 50/50 with expensive paint to make the tube last twice as long without changing the consistency.
For impasto: Use Heavy Gel to make cheap, runny paint feel like thick oil paint. It holds peaky brushstrokes and knife marks.
As an adhesive: It's the best glue for collage. It bonds paper to canvas permanently.
2. Modeling/Molding Paste
The Difference: Gels are flexible plastic. Paste contains marble dust (calcium carbonate).
The Result: It dries rock hard, opaque white, and rigid.
The Superpower: You can sand it, carve it, or drill into it like wood. Use this to build 3D structures on your canvas before you paint.
Warning: Do not use on flexible surfaces (like thin paper) or it will crack when rolled. Use it on rigid panels.
Flow Modifiers (Fluids)
These change the movement of the paint. They make it thinner or more slippery.
1. Glazing Liquid (or Glazing Medium)
The Look: Thin, milky liquid.
The Use: The secret to the "Old Masters" look. It turns opaque acrylics into the look of transparent stained glass.
Technique: Mix a tiny dot of color into a pool of glazing liquid. Paint it over a dry image to tint it (e.g., turning a black and white grisaille painting into color).
2. Flow Improver
The Physics: Water has surface tension (it beads up). Flow Improver breaks that tension.
The Use: It makes the paint "slippery." It allows you to paint long, continuous lines without the brush running dry.Critical Rule: This is an additive, not a medium. It contains no binder. Do not add more than 10% to your paint, or the paint will never dry properly.
3. Pouring Medium
The Trend: The "Dirty Pour" or "Fluid Art" phenomenon.
The Physics: It thins the paint to the consistency of honey but keeps the colors separated so they don't mix into mud. It is "self-leveling," drying to a perfectly smooth, glass-like finish.
2. Matte Medium
Effect: Contains matting agents (white powder) that kill the shine.
Use: Good for photographing art without glare.
Warning: Because of the matting powder, it can look "milky" or "foggy" if you layer it too thickly over dark colors.
The Trend: The "Dirty Pour" or "Fluid Art" phenomenon.
The Physics: It thins the paint to the consistency of honey but keeps the colors separated so they don't mix into mud. It is "self-leveling," drying to a perfectly smooth, glass-like finish.
Time Modifiers
Acrylics dry in minutes. Sometimes you want them to stay "open" like oils.
Slow-Dri / Retarder
The Function: It contains chemicals (glycol) that inhibit evaporation.
The Result: It keeps your paint wet on the canvas for 30–60 minutes instead of 5.
Why use it: Essential for blending smooth gradients in skies or skin tones. Without it, your paint dries before you can finish the blend.
Warning: If you add too much, the paint will remain tacky for weeks. Follow the bottle instructions (usually max 15%).
Sheen (Gloss vs. Matte)
Most acrylics naturally dry to a semi-gloss (satin). You can force them one way or the other.
1. Gloss Medium
Effect: Makes colors look wet, deep, and saturated (like oil paint). It increases contrast.2. Matte Medium
Effect: Contains matting agents (white powder) that kill the shine.
Use: Good for photographing art without glare.
Warning: Because of the matting powder, it can look "milky" or "foggy" if you layer it too thickly over dark colors.
Benchmark Brands
Liquitex
The System: They color-code everything perfectly. Green label = Slow Dri. Red label = Super Heavy.Verdict: The best system for beginners to understand what they are buying.
The Quality: Higher solid content. Their "GAC" (Golden Artist Colors) line of specialty polymers is for chemical nerds who want exact control.
GAC 100: Universal polymer (thinner).
GAC 800: For pouring (prevents crazing).
ArtHero's Verdict
The Essential Mediums:
Liquitex Gloss Gel Medium.
Why: It does everything. It extends your paint, works as glue for collage, and adds transparency.
Golden Retarder or Slow-Dri Fluid.
Why: If you are frustrated by your paint drying on the brush, this solves the #1 complaint about acrylics.
The Avoid List:
String Gel / Tar Gel.- Unless you are doing very specific "drizzle" abstraction (like Jackson Pollock), this sits on the shelf unused.
- It’s a gimmick. It looks like a craft project, not fine art. You can achieve better textures naturally.