Understanding the Different Types of Paint Thinners and When to Use Them

Paint thinners are used to make paint easier to apply, but it’s not as simple as that. You need the right thinner, in the right amount, for the right paint system. Get that wrong and you can easily ruin a perfectly good tin of paint.

In this article, we explain the different types of paint thinners and why compatibility with your paint is so important.

What are Paint Thinners?

Paint thinners are solvents used to adjust how a paint behaves during application by controlling its viscosity, flow and evaporation rate. When used correctly, thinners help ensure proper atomisation during spraying, improved flow and levelling, and a consistent finish across the coated surface.

Paint thinners are not universal products. A thinner suitable for one resin system may be incompatible with another. Using an incompatible paint thinner could potentially cause curing issues, loss of gloss, poor film formation or resin separation.

What are Paint Thinners Used For?

Paint thinners are used to dilute paint in order to make it easier to apply, especially when used with spraying equipment. They are mainly used for:

• Thinning the viscosity of the paint for application type, brushing, rolling or spraying 

• Improving flow and levelling 

• Achieving the correct atomising when spraying 

• Controlling drying and curing behaviour

• Cleaning application equipment

Why is Paint Thinner Compatibility so Important?

There are many different thinners on the market, each formulated to be compatible with specific paint systems. Because each paint system uses a particular resin chemistry, the thinner must be chemically compatible with that resin for the coating to dissolve correctly, flow properly, and cure as intended. Different resins behave differently, which is why a one-size-fits-all thinner does not work. Some solvents simply do not work well with certain pigments or with other solvents already present in the paint.

You will save yourself time and frustration by sticking with the thinner made for the paint you are using. The people who manufacture the paint know exactly which thinner works best with their formulation, as it has been tested to deliver the correct flow, drying behaviour and finish quality.

Always consult the paint manufacturer and use the recommended thinner, as systems are tested together. Following their guidance is the best way to avoid application problems.

What Problems are Caused by Using the Wrong Thinner?

Using incompatible paint thinners can cause – 

• Poor drying or incomplete curing

• Loss of gloss and reduced finish quality

• Adhesion failure or surface blooming

• Resin separation or coagulation, resulting in a grainy or “bitty” appearance

• Increased or unstable paint viscosity, leading to application difficulties

Always check the manufacturer’s recommendations for the correct thinner, and if in doubt, test the mixture on a sample piece first.

What are the Different Types of Paint Thinners?

White Spirit 

White spirit is mainly used with oil-based paints and single-pack polyurethane coatings that are formulated using white spirit as their base solvent.

Xylene 

Xylene is used in quick-drying paints and primers typically used for industrial use. It's ideal for adjusting paint viscosity and is suitable for spray, brush and roller applications. 

Standard Thinners 

Standard thinners are usually general-purpose solvents. They are most commonly used for cleaning spray guns, brushes and other application equipment rather than thinning paint for application. 

Epoxy Thinners 

Epoxy paint thinners are used to thin down epoxy paints and primers. They reduce viscosity to make the application easier without interfering with the chemical curing process that epoxies rely on. 

2K Acrylic Thinners

2K acrylic thinners are used as part of a full paint system alongside the base paint and hardener. They control sprayability, flow, evaporation rate and final finish quality. Because 2K systems are chemically reactive, using the correct branded thinner is critical for both performance.

Cellulose Thinners

Cellulose thinners were commonly used in older paint systems; they are generally unsuitable for modern industrial coatings. Today, paint-specific thinners provide better control over application, curing and finish quality.

Read our Quick Guide to Paint Thinners for more practical tips on using thinner for paint.

How Much Thinner Should Be Added to Paint?

The amount of thinner you need to add to paint depends on the type of paint being used and the application method, whether it is brushing, rolling or spraying. There is no standard amount that works for every product. The correct thinning ratio will always be stated on the paint’s Technical Data Sheet (TDS), usually as a percentage. Adding too little thinner can make the paint hard to apply and affect atomisation when spraying. Adding too much can weaken the coating and damage the final finish.

Can You Over-Thin Paint?

Yes, you can absolutely over-thin paint. Over-thinning happens when too much thinner is added and the paint’s viscosity becomes too low to form a proper coating. This reduces film build, weakens durability and often leads to poor coverage and loss of gloss.

Over-thinned paint is also far more likely to sag or run. This makes application difficult and usually results in an uneven or poor-quality finish that needs reworking.

The best way to fix over-thinned paint is to bring the mix back to the correct consistency rather than trying to work with it.

Add more paint

The simplest and most reliable fix is to add more of the original, un-thinned paint. This increases the viscosity and restores the correct balance of resin, pigment and solvent. Always mix thoroughly and recheck the consistency before applying.

Paint Thinners at TA Paints

At TA Paints, you’ll find a range of thinners and solvents designed to work with specific paint types and application methods. As manufacturers and suppliers of industrial coatings right here in the UK, our thinners are selected to match the coatings we offer. 

Our range includes quick-drying xylene-based thinners, universal epoxy thinners and white spirit options. They are all available in multiple sizes with free delivery deals and bulk discounts to suit trade and industrial projects.

If you’re unsure which thinner is right for your application, contact our expert team today. We’re on hand to help you choose the correct product for metalwork, machinery, vehicles or structural surfaces, so you get the best performance and a professional finish every time.