Why Is Your Oil Paint Clumping? Common Causes and Fixes 

Why Is Your Oil Paint Clumping

You’re new to painting with oil paints, and your paint is clumping instead of mixing smoothly. Is your paint ruined? Why is this happening, and what should you do?

Your oil paint could be clumping because it’s old, dried-out, or very low quality. Mix with a solvent and smooth with a palette knife to get the lumps out. Using too much thinner can also cause the binder in the paintOpens in a new tab. to dissolve and the pigment to clump. In that case, use less thinner.

This article will explore three common causes and fixes for lumpy oil paintOpens in a new tab.. I will also include tips on using thinners and recommendations for alternative solvents. 

One – Your Paint Is Old

Old paintOpens in a new tab. is the number one reason for clumps. When oil paint begins to dry out, it gets thicker and forms lumps. This can occur quickly with cheap paints, but high-quality paints should only get lumpy if the tubes are punctured, left open, or extremely old. 

Using a traditional paint thinner like turpentine is the easiest way to combat this issue and revive your old paint.

How to Fix

Mix the lumpy paint with turpentine on a flat surface using a palette knife (not a paintbrush). Use turpentine only a little at a time to avoid over-thinning the paint and ruining it. Always use turpentine in a well-ventilated area, and avoid breathing the fumes or getting it on your bare skin.

You can add other mediums like linseed oilOpens in a new tab. to thin your paint and slow the drying time, but use it with a solvent like turpentine. Mix the linseed and turpentine into your paint in about equal measures for the best results. 

Note: It’s best not to use too much linseed oil for the early layers of your painting, as you want those to dry faster. In addition, using too much linseed oil can cause the yellowing of the paint as it dries. 

Two – Your Paint Is Cheap

It’s perfectly reasonable for beginners to buy cheap oil paints, but if your paints are too cheap, they may come out of the tube already lumpy. Cheap paints contain fillers and drying agents to make the pigment go a little farther and ensure that the different colors dry at equal rates. Low-quality tubes may dry out faster on the shelf as a result. 

How to Fix

Try using turpentine as described above. However, if your paints are new and they come out of the tube lumpy, it may be worth the investment to buy some higher-quality paints. Cheap paint can also separate inside the tube before they’re ever opened, which makes them unusable. 

*High-quality oil paints dry at different rates depending on color/pigment. Beginner paints have added drying agents to make their use easier for novice painters. 

Three – You Used Too Much Thinner or Medium

Sometimes, beginners may go overboard with the thinners and mediums. That’s okay, though! It’s part of the learning process. However, adding too much solvent or other mediums can cause the pigment and fillers/binding agents in your paint to separate. 

This is especially true if you’re using low-quality paints, as they already contain extra fillers. The result is little clumps of pigment swimming in oil, which is irreversible. 

Separation can also occur because of a reactionOpens in a new tab. between the paint and a particular solvent, filler, or medium. Some paints may even begin to separate inside the tube immediately after it’s sealed and packaged. 

How to Fix

Add solvents, thinning agents, and other mediums a little at a time until you get the consistency you want. I always recommend mixing with a palette knife for smooth and evenly mixed paint.

Suppose you have repeated problems with your paint separating, and you’re sure it’s not due to excess thinner. In that case, it is likely a reaction between something in the paint and whatever medium you add. In this case, investing in higher-quality paints and/or trying different mediums to get your desired consistency is best.  

Alternative Solvents and Thinners

I’ve mentioned turpentine and linseed oil as the go-to thinners for oil paints. Still, there are several alternativesOpens in a new tab. that won’t fill your studio with toxic fumes. In fact, the solvents listed below are considerably more environmentally friendly than turpentine and just as effective!  

Gamsol Oil (OMS)

Gamsol, a.k.a. odorless mineral spirits (OMS), is a solvent distilled from petroleum, but it’s much safer than turpentine. However, it can still be damaging to the skin, eyes, and lungs with prolonged exposure. 

Tip: Make sure to buy artist-quality OMS as commercial versions have additives that don’t mix well with paint. 


Turpenoid is turpentine’s odorless cousin. This solvent is used for thinning oils and varnishes. It’s not precisely non-toxic, but it doesn’t produce intense toxic fumes like turpentine. 

Tip: Use in a well-ventilated area and buy a lidded, leak-proof brush washer to contain the fumes.

Citrus Solvent

Citrus SolventOpens in a new tab. is a safe, non-toxic alternative to turpentine, made almost entirely of citrus peel oil. This solvent won’t damage the environment, and it smells great! This is an exceptionally environmentally friendly choice because it’s biodegradable. 

It also won’t damage your paint brushes over time, like turpentine and other harsher solvents, by leaching the natural oils from the bristles.

Tip: It can be used to thin oil paints for use with dip pens and can be mixed with oil-based inks, oil pastels, and wax-based products. 

Lavender Spike Oil 

Lavender spike oil is a type of essential oil. For centuries, spike oil has been used as a natural, plant-based, non-toxic thinner for oil paints, resins, and varnishes. As you might expect, it’s pretty expensive. However, it’s totally organic and biodegradable.

Tip: It can also be used for aromatherapy, skin treatments, perfumes, and soaps. 

Final Words

Oil paints become lumpy when they are old and dried out or mixed with too much thinner. Low-quality pains can also become clumpy due to the separation of the pigments from oil and fillers. The best way to fix old and dried oil paint is to mix it with a solvent and smooth the lumps out with a palette knife.

waddellwebisodesOpens in a new tab.
Was this article helpful?


Ines is a self-taught artist based in the UK. Originally from Caracas, she has dabbled in the world of arts and crafts in a diversity of ways participating in city intervention projects, sustainable practices’ open exhibitions, and her illustrations being featured in anniversary editions of literary magazines.

Recent Posts