How to Easily Thin Out Thick Acrylic Paint

Easy methods for thinning out thick acrylic paint and add more versatility to your paintings

how to thin out thick acrylic paint

You probably encountered this problem before. You stare at your landscape painting, want to add a subtle blend, a hint of a certain color to that beautiful sunset sky, or get a super fine thin line for your tree branches.

So you pull out your paint tube and squeeze a dollop onto your palette, but to your utter dismay, the paint itself is just way too thick! Using it in its original thick state would easily overtake the painting, like a bull in a china shop, totally making it harder for you to create that sexy smooth sunset blend or that fine-looking thin branch. What is a poor, distraught artist to do in such a situation!?

Lucky for us, the answer is quite simple.

The best strategy would be to thin out your acrylic paint, either by using water, adding an acrylic medium to properly dilute and thin out the paint, or buying paint with your desired consistency.

Alright, so thinning out acrylic paint is a great idea, but it presents a myriad of additional questions:

  • How much should I add?
  • How much is too much?
  • What specific types of acrylic mediums can I use without ruining the paint itself?

In this post, we’ll dive into these questions and explore them even further.

How much water can I add to acrylic paint?

One of the easiest ways to thin out acrylic paint is by adding water to it.

However there are few things to keep in mind when diluting paint with water. Water actually breaks down the binders in acrylic paint, thinning the paint to resemble that of watercolors, allowing it to sink into the surface of the support and dry with a matte finish.

Adding too much water however can cause the binders to break down so much that the paint won’t be able to adhere together or provide good coverage. Plus, after your paint dries, there is a great likelihood for the paint to chip or flake off the canvas. Blegh, that would suck!

So, if that is an effect you want to avoid, consider adding 25-30% water to your paint to dilute it.

To take this even further, you can use super diluted acrylic paint to create pretty watercolor effects!

I have created watercolor effects just by using acrylic paints, diluting it with a lot of water (about 60%) and creating washes and layers of color. So really, it’s up to you what effect you want to go for at the end of the day.

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What acrylic mediums can I add to acrylic paint to thin it out?

Another way to thin out acrylic paint is to mix in various acrylic mediums with your paint. A big advantage of using these mediums is it maintains the integrity of the acrylic binders, therefore you’ll still get coverage no matter how much medium you add. The paint will simply thin out and become more transparent the more medium you add. It also allows the paint to sit on the surface of the canvas or support, keeping it’s glossy finish.

Now, what kinds of acrylic mediums are good for thinning out acrylic paint? Some include the following:


There are two approaches to using gesso to thin out your paint.

And just in case you have no clue what gesso is, it’s basically a white (or clear) paint mixture consisting of a binder mixed with chalk, gypsum, pigment, or any combination of these. Gesso is fantastic for prepping and priming surfaces for painting – in fact, most canvases are already pre-coated with gesso for easier paint application.

One is to prime your canvas or final support with gesso so that whatever paint you add on top will not absorb into the support itself. This is really important for the use of thin paint, especially if you want to create a more wash-like or stain effect with your thinned out paint.

The second approach would be to actually mix the gesso and acrylic paint together to thin it out to your desired consistency. Since you probably want to keep the same color/tone of your desired paint, I would recommend choosing clear gesso to do your thin bidding.

Read more: How to reuse or fix any canvas for new paintings

Thinning/anti-congealing agents

Acrylic paint thinners that provide anti-congealing capabilities can be a great option to thin out your acrylic paint. Two paint thinners that come to mind include:

  • Golden Open Thinner (the art company Golden has created an acrylic thinner that can not only thin your paint, but also slow down the drying time of your acrylics)
  • US Art Supply AirBrush Thinner (even if you don’t work with airbrushes, airbrush thinners are really great at thinning acrylic paint without compromising the paint coverage or color. You’ll have to add a bit at a time into your acrylic paint to get your desired texture)

Acrylic glazing liquids

Acrylic glazing liquids can serve as a way to thin out acrylic paint and are usually milky white in appearance and have a slight runny quality to them. Some glazing liquids have slow-drying paint extenders pre-mixed in that can be used to keep your acrylics from drying too quickly and can dilute your paint strokes without compromising canvas coverage (which water has been known to do with acrylics). When mixing this in with your paint, you can continually add glazing liquid to further dilute your coverage – making it really awesome for subtle blending edges.

One of the more reputable acrylic glazing liquids that extend your painting time is Golden Glazing Liquid. It helps thin out your acrylics, keep them wet for a while longer and is available in gloss and satin finish.

Golden Gloss Glazing Liquid
Golden Satin Glazing Liquid

Read More: 5 Easy Ways to Keep your Acrylic Paint Wet for Longer

Flow improvers

Flow improvers help break down paint viscosity so it can better flow and spread on canvas, without compromising color strength or saturation. I have commonly seen these types of thinners for fluid pour artworks which need a higher flow rate, but these can also be used for other painting projects as well. Some great flow improvers include the following:

How much acrylic medium can I add?

That would depend on the acrylic medium you are using and their specific instructions on the packaging; but as a rule of thumb, consider adding medium a bit at a time to your acrylic paint and observe the resulting mix and transparency. Because you’re not dealing with water (and the resulting breakdown of binders), you can add acrylic medium without careful observation of specific ratios or compromise of paint coverage capabilities.

Can I thin acrylics with household items?

Yes, you can. There are a fair amount of artists that have resorted to their kitchen or pantries to help thin out their acrylics, much to their success. Some common household items you can use include the following:

  • Hydrogen peroxide
  • Pledge Floor Shine
  • Fantastik Cleaning Spray
  • Rubbing alcohol (30%-60%)

Can you use alcohol or acetone to thin acrylic paint?

Some artists swear by using isopropyl (aka rubbing) alcohol for thinning their paints, and this is relatively true but with a caveat. High concentrations of rubbing alcohol (90%+) can actually gum up your acrylic paint and cause it to gather like cottage cheese. No bueno!

So if you are looking to use rubbing alcohol to thin your paint, opt for lower concentrations (30-70%) or dilute the alcohol with water before mixing with your acrylic paint.

As for acetone, the same general idea applies.

Undiluted acetone might be far too strong when thinning acrylic paint, so its best to first dilute 50% of it with water and add little bits to the acrylic paint at a time until you get your desired consistency.

Can you thin acrylic paint with commercial paint thinner?

Yes, you can use commercial paint thinners, but it’s not an option I would always recommend. Commercial paint thinners tend to contain more chemicals and can emit powerful fumes that may be toxic if mishandled. If you choose to work with commercial paint thinners, consider working in a well-ventilated area or outdoors. And in the same vein as rubbing alcohol and acetone, you’ll want to first dilute the paint thinners first with water before directly applying it to your acrylic paint. Test small amounts at a time until you reach your desired consistency.

What should I avoid?

When thinning acrylic paint, there are few things you’ll want to avoid mixing with the paint so as not to mess with the binders or consistency. They include the following:

  • Ammonium
  • High concentrations of isopropyl alcohol
  • Vinegar

What else can I do to thin out my paint?

Pick the right brushes

Ok, why are we talking about brushes in relation to thin paint? How is this relevant?

Well, the type of brush you choose to create a background or fine detail can lead to create more layers of paint or load more paint than you intend.

Take painting backgrounds for example. If you still find yourself struggling to get that perfect spread of thinned paint, struggle-bussing with a #10 shader brush to create a smooth background color is just not the right call or use of your time. Instead, when trying to create blends or apply wide applications of thin paint, consider using a wider brush (perhaps a 1″ flat wash brush) to help you cover more area and evenly apply your thin paint without the need to create more layers than you want.

Along the same vein, if you are looking to create fine strokes for blades of grass or create sharp, crisp lines for trees and branches, a #10 shader brush may not be the best choice. Instead, opt for a smaller detail round brush that can take just the right about of paint to achieve those razor crisp lines you are looking for. Plus, using either water or acrylic mediums mentioned above will significantly increase paint flow for optimal stokes!

Buy the right paint

If you want to avoid having to use any additional mediums or just feel there are way too many steps to get your desired paint thinness, buying the paint with your desired consistency is a great option.

So what do you specifically look for? The answer is paint viscosity.

There are 3 famous types of paint viscosities, which include the following:

  • Heavy body acrylics: a peanut-buttery, paste-like consistency of paint that is great for palette knifes, impasto-style paintings, and textured brush strokes.
  • Soft body acrylics: a soft, creamy paste with the consistency of custard that is great for brush details, glazes, undercoats, or painting large flat areas.
  • Liquid Acrylics: a free-flowing, extremely diluted with pigments paint with the milk-like consistency, liquid acrylics are ideal for paintbrushes, airbrush and frescoes (to name a few).

If your go-to acrylics were always heavy body paints but you continually struggle thinning them out, try working with either soft-body or liquid acrylics. Soft body acrylic paints are usually a good-middle ground paint for lots of projects and is one I prefer because I can add a small amount of water to get amazing thinned out paint with great flow.

What are your thoughts about my acrylic paint thinning tips? What have you used to thin out your acrylics? Comment and share below!

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