Painters Series: Cutting Paint With Water: Smart Shortcut or Costly Mistake?

We will be writing a number of blog posts on this contentious topic, I’ve been successfuly doing it for decades in certain situations and for the right reasons and I just wanted to share my experiences with you.

If you've ever talked to a painter—or watched a few DIY videos—you've probably heard the phrase "cut the paint with a bit of water." Some people swear by it. Others say it's the fastest way to ruin a job. Like most things in painting, the truth sits somewhere in the middle.

Cutting paint with water simply means diluting it slightly to change how it behaves. It's common, it's controversial, and when done wrong it can absolutely backfire. Let's break down why people do it, when it makes sense, and when you should absolutely not touch that lid with a water jug nearby and other by-products of this contentious topic.

The first post in this series is titled “Why People Cut Paint With Water”, the subsequent posts will build on this topic by talking about the pro’s and con’s, tools, techniques and related.  Enjoy the post and if you enjoyed it, come and visit us on our social media: IG @martythepainter FB Marty’s Painters Tools

Why People Cut Paint With Water

There are a few main reasons painters thin paint:

1. Easier application

Thinner paint flows more easily. It can reduce drag when rolling or brushing, especially with thick modern latex paints. This can make cutting in edges smoother and reduce visible brush marks. Modern paints are formulated thicker than older generations—manufacturers have increased solids content to meet VOC regulations and provide better one-coat coverage. While this improves performance in many ways, it can also make the paint feel heavy and sticky on the brush or your paint roller.  A little bit of water can reduce this drag without compromising the integrity of the paint, and no you won’t need to add a second coat, unless you would have needed to originally.  Another benefit is it can reduce the severity of the overlap lines between roller applications.    

2. Better spray performance

If you're using a sprayer, paint often must be thinned to atomize properly. Too thick and you'll get spitting, clogging, or heavy orange peel. Different sprayer types have different requirements. HVLP (high volume, low pressure) systems typically need more thinning than airless sprayers, which can handle thicker materials. The tip size on your sprayer also matters—a .015 tip requires thinner paint than a .021. Ignoring these realities doesn't just give you a bad finish; it can damage your equipment and turn a two-hour job into a full-day cleanup.  Try applying thinned paint on a test surface or on an area of your next job that it won’t matter if the shade is different.  

3. Cost stretching (the bad reason)

Some people dilute paint to make it go further. This is common in low-bid jobs or rentals where appearance matters more than durability. You'll see this with landlords prepping units between tenants or contractors trying to salvage a bid they underbid. The walls might look acceptable at move-in, but six months later they're showing every scuff mark and handprint. This practice gives thinning paint a bad reputation it doesn't entirely deserve—the problem isn't the technique, it's the motivation.

4. Hot or dry conditions

In warm or low-humidity environments, paint can dry too fast. A small amount of water can slow drying time and improve leveling. Anyone who's tried to paint a south-facing wall in July knows the frustration of paint drying before you can work it out. The paint sets up so fast you can see lap marks forming in real time, and brushstrokes freeze before they have a chance to flow out. In these situations, a measured amount of water isn't cheating—it's adapting to the conditions.

5. Working with aged or thickened paint

Paint that's been sitting for months or years can thicken, even in a sealed can. The water in latex paint slowly evaporates through the plastic container, especially if it's been stored in a hot garage or shed. Rather than throw it out, a small amount of water can bring it back to workable consistency. This is different from diluting fresh paint—you're restoring it to its original viscosity, not weakening it.

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