How to Thin Epoxy

thin epoxy resin pouring

You’ve loved epoxy projects and have scrolled Pinterest and Instagram endlessly to see the effortless beauty of aesthetic epoxy flowing across river pour art, serving trays, and even countertops. But when you try to work with epoxy, it is sludge harder to pour than tar. This can be confusing, but one can easily thin epoxy to make it easier to work with for pouring projects.

To thin epoxy, you must first transfer it into another container and add one-tenth paint thinner to the transferred quantity. You should then stir it with a stick-like utensil that you don’t plan to use later. After the thinner has vanished into the epoxy, you can work with the resin as intended.

In this article, you’ll learn everything you need to know about thinning epoxy, including what happens when you use the wrong thinner or mess up proportions with the right diluent. You’ll also discover other ways to make epoxy easy to work with, even when you can’t thin it. Above all, you’ll find out how to safely portion your epoxy so there’s room for error and a mistake in thinning doesn’t ruin your whole epoxy batch.

Picking the right diluent is a key part of getting a functioning low-viscosity epoxy. If you use the wrong product to thin your epoxy, the proportions don’t matter because either result will be virtually unusable. When you use the wrong thinner, you can end up with a sludge that never cures. 

In other instances, the thinner doesn’t actually mix with epoxy and forms bubbles or layers inside the epoxy. When epoxy cures, it is either bumpy or has a visible layer of thinner suspended in it. Of all the diluents one can use, one of the worst ones is water. 

And it’s bad mainly because of how easy it is to use for novices. If you’re reading this article, you already know better than to use just any liquid lying around the house to make your epoxy thinner. Many people don’t, and they add water to thin the epoxy as if diluting juice.

The right diluent is an alcohol-based one, ideally a paint thinner. These thinners have construction-grade resilience, so they are reliable additions to the epoxy. 

Of course, picking the right thinner doesn’t mean you can add as much as you want. It’s always better to err on the side of less, though, because the problem with less thinner (low working time) can be fixed by adding more. But once you’ve added thinner, taking it out becomes harder. In such cases, you have to resort to pouring more epoxy.

If you add too much diluent and don’t balance it with epoxy, the curing time will become so long that the project will be at risk of damage from the environment. 

Usually, you don’t want the epoxy to take any more than 24 hours to cure. If you add too little thinner, the epoxy will be harder to work with and might trap bubbles but will cure just in time. 

An expert can get away with pouring epoxy with little thinner and turning out a perfect product. But epoxy with too much thinner is something even most experts have a tough time working with. With the foundations established, let’s look at the steps you must take to thin epoxy.

Step 1 – Start With Half the Amount of Resin

You must start with half the amount of resin you need because this gives you a 50% margin of error. In other words, if you mess up the ratios, you’ll be able to add epoxy without having a surplus. Epoxy is expensive, and this small step can save you a lot of money. Pour the epoxy into a wide container while being mindful of its curing time and conditions.

Step 2 – Add One Part Paint Thinner for 10 Parts of Epoxy

This one is a straightforward step that people get wrong only because they try to aim for a total of ten. A simpler method is to simply divide the amount of epoxy by ten and pour that much thinner. So, let’s suppose you want 1 gallon of epoxy for the project, and you start with half to be safe. 

Dividing 0.5 gallons of epoxy by 10, you get 0.05 gallons. That’s the amount of thinner you must add at this step. 0.05 gallons equal 0.189 liters and since this degree of precision isn’t possible for most household DIY projects, remember to err on the side of less. So, going for 0.15 liters or less thinner would be ideal.

Step 3 – Stir Using an Appropriate Utensil

This is dictated entirely by how big a project you have on your hands. If you’re working with a cup’s worth of epoxy, you can use any spoon you plan to throw away later. But it is also possible that the project you’re working on will encompass your entire floor. In that case, using an entire shovel to mix the epoxy in a barrel will make more sense.

Step 4 – Lay the Epoxy

Yes, the next step isn’t to repeat the same steps with the rest of your epoxy even though you currently have only half the thinner. This step helps keep your epoxy from curing at an inopportune time. 

Work with the half that you have thinned and return to the remaining epoxy when you’re done with this. In some cases, you do need the entire batch in one go, which is where flipping this step with the next one makes sense.

Step 5 – Thin the Rest of the Batch

Using the same ratio and steps outlined in steps one through three, then the remaining batch, so you have enough epoxy to finish your project. Once the epoxy is thinned, proceed with the project as intended.

It is worth remembering that pouring thinner first is not an option as thick epoxy can easily form a layer over it and keep your stirrer from reaching the diluent when you try to stir it. Always pour epoxy first. If you want to skip the steps above and make epoxy easy to pour without thinning it, then you should get comfortable working in very hot environments. 

It turns out the hotter the environment, the easier epoxy pours. And while adding thinner means you get to work in relatively colder conditions, you cannot pour hardener to fix the long curing time. 

You will need to protect your epoxy from bubbles, dust, and pets or kids for a longer time when you operate with thin epoxy. If the reason you want to thin epoxy is that it traps bubbles when you leave it to cure, then you’re thinking along the right lines.

Using a thinner like Sunnyside Lacquer and Epoxy Thinner will reduce the bubbles that might get trapped during the curing process. I like this product more than average paint thinner mainly because Sunnyside has cared enough to segment a thinner product specifically for epoxy. 

Given the appetite for epoxy products, it makes sense that this much-needed thinner has over 1,900 reviews and ratings on the site, with most of them positive. The collective rating of Sunnyside Epoxy Thinner is 4.5 out of 5 stars. A great average for that many reviews.

Final Thoughts

Thinning epoxy isn’t rocket science but requires the same seriousness as working on a rocket. Spilling too much thinner can drag the cure time, while using the wrong diluent can ruin your epoxy batch. Follow the steps in the post above (or recapped below) to do this right.

  • Add epoxy to a different container
  • Add one-tenth of the same amount of thinner into the same container
  • Stir with a spoon or an appropriately sized clean stick
  • Lay the thinned epoxy as intended

Damien Madeira

Damien has been doing woodworking for the last 5 years. He began as a hobbyist with hand tools and slowly worked his way up to own larger machines and mill rough wood into beautiful creations. While still considering himself a hobbyist, he has a passion for woodworking and enjoys working with epoxy as well.

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