Acrylic Additives vs Mediums

Hey guys! So I just realized something…lately I’ve been talking a lot about mediums I like to use and additives and how to avoid the biggest mistake acrylic painters make, and I’ve just realized that I don’t have a dedicated blog post to sharing the difference between additives and mediums!! What??? What am I doing with my life?

I thought for sure I had written about this before, but apparently I haven’t.  I’ve touched on various mediums to prime and finish your work and types of acrylic paint, but not exactly what the difference is between additives and mediums. I explain the differences in my Acrylic Painting for Absolute Beginner’s Ebook, so perhaps that’s where I feel like I’ve written about this before.

So enough rambling! Let’s get on with the difference between additives and mediums once and for all!

What's the difference between acrylic additives and mediums?

If you’re interested in checking out any of the mentioned mediums or additives in this post, I’d greatly appreciate you clicking the affiliate links I’ve included to Amazon to help support this blog at the same time, thanks!

I’m going to try to keep this as short and sweet as possible.  Let’s take a moment to think about what makes up acrylic paint.  Acrylic paint is basically pigment (the color) mixed with a vehicle to deliver the pigment to the surface we’re painting on.  In acrylics, that vehicle is a polymer structure that dries to a plastic-like finish.  It’s this vehicle, or “glue” that holds the pigment, that gives acrylics their signature sturdy composure.  When acrylics are fully cured they’re flexible, crack-resistant, dirt-resistant, and waterproof. It’s the polymer structure that gives it these properties.

So mediums that we use to change the texture or fluidity of our paint have their own structure.  An acrylic medium is basically the same polymer vehicle that makes up acrylics, without the pigment.  In place of the pigment, we have other materials that give us the effect we want (ground pumice stone in pumice gel, that stringy texture in clear tar/string gel, or even just more of the polymer vehicle in heavy gel).

Golden's Heavy Gel, a medium for increasing the thickness of your paint.
Golden’s Heavy Gel, a medium for increasing the thickness of your paint.

So to sum it up, acrylic mediums are composed of the same “glue” that holds the paint together.  This is why we can use acrylic mediums in unlimited quantities, and mix them with each other in whatever ratios we want without changing the integrity of our painting.

Additives, on the other hand, are something completely different.  Acrylic additives do not contain the polymer structure within them, so by adding them to our paint, we’re diluting the “glue” that gives our paint its strength.  Adding too much additive can create gaps between the polymer structures, preventing them from meshing together in their strong formations when cured.  This means that if too much additive is used with out paint, our painting has the risk of cracking in the future, or even not fully curing at all and remaining in a horrible tacky consistency forever!

Acrylic Flow Release
Acrylic Flow Release, an Additive

So how do we know how much additive is too much? It will tell you on the container.  Just be sure to follow the directions and not use too much. Additionally, you can mix your chosen additive with a medium that works well with it, so you’re basically adding some “glue” to the additive.  I personally like to mix in a bit of glazing medium with my flow release additive that I add to my misting bottle for spraying my paint to make it run down the canvas.


So there it is, guys! The difference between acrylic additives and mediums.  Both are great and can really help you express yourself with acrylics, as long as you know what you’re using and how to use it.  Leave me a comment below if this post helped you, and thanks for stopping by! Till next time, keep creating!

-Ashley <3

What's the difference between acrylic additives and mediums?

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