How to Thin Epoxy – Steps and Tips for Thinning Epoxy

This post may contain affiliate links. We may earn a small commission from purchases made through them, at no additional cost to you.

If you are a newbie to epoxy resin, then you should be aware that good mixing and preparation skills are essential. You should adhere to instructions since you will be dealing with polyoxides. The only troublesome thing about epoxy resin is its thickness and viscosity, making it hard to apply. Thus, also preventing it from getting into the dings and nicks of the surface. This article will enlighten you on how you can fix this problem with much ease.

Epoxy Resin

Epoxy resin is a thick, strong material that is mostly used as a sealant and adhesive in most projects. It is considered a very solid and strong material usually used in construction and building applications. This substance is thick and viscous.

However, the thickness and viscosity features of epoxy can pose problems. These features make it hard to apply epoxy. Thus, bad coverage causes the resin to cure improperly by creating pockets of air. The solution to this problem is to thin the epoxy resin.

Thinning Epoxy Resin

This process is done by lowering the viscosity (state of being thick in consistency).  Doing so will enable the epoxy to flow better because the consistency becomes thinner. Thin epoxy is also easy to use, for instance, it becomes easy to roll and brush. Two methods are used for temporary epoxy thinning are heating the substance material or adding a solvent.

Note: Some of the epoxy thinning methods can lower its viscosity, thus affecting the properties of the substance as well. 

Heating Method

This method is not popular as the solvent method, but it can thin the epoxy resin, without weakening it. You can do this process by applying heat to the surface before applying the epoxy. The heat will thin down the epoxy to a workable size. A good example that can be used to see how heat works on a resin is canned cake frosting which is originally thick, but when it is heated it becomes thin and easy to pour.

If you want to try the heating method then you should start by filling a bathtub/bucket with hot water, preferably boiling water. Place the can of the resin inside the boiled water. Leave it to sit for a short while. The epoxy resin will become thinner because of the heat of the water which conducts effectively with metal. Apply the resin quickly before it cools down to its normal state.

However, thinning epoxy with heat should be done with some caution. This is because epoxy cures quite fast, so you need to organize your things first before you do the mixture of the hardener and resin. Choose a slow hardener like a 206, 207, or 209.

A slow hardener is useful in increasing the working time. Make sure the containers are warm enough for at least 115 degrees Fahrenheit. This is because too much heat quickens the hardening time of the epoxy. This will be bad if you are doing thick applications. The epoxy will be overheated if the cure happens quite rapidly. If you notice any smoke during the curing of the epoxy, then it means that your epoxy would have been damaged.

Solvent Method

This is the most harmful method of thinning epoxy, but the most used method. This method is harmful because it damages and weakens the epoxy. Even though the epoxy varies from brand to brand, the 5% thinner that is added to the mixture can decrease its strength by 35%. Handle this process with caution because the solvent has a direct effect on the performance of the resin. Once the performance has been affected, there will be an increase in the curing time of the epoxy. However, there are a few downsides to using a solvent to thin epoxy. These include:

• A solvent increases the risk of fire
• A solvent like acetone affects the cured epoxy`s color
• The solvent can cause the epoxy to shrink/crack
• A solvent increases the curing time
• A solvent weakens the epoxy`s strength

Using Acetone

You can use acetone or paint thinner interchangeably to make epoxy thinner. However, exercise a lot of caution when doing this process because these solvents can weaken the epoxy resin. Moreover, if you mix the substances incorrectly the finished product will be ruined. So be sure to follow the general rule of thumb by mixing the thinner at a ratio of 10:1. This means that one gallon of acetone is enough to thin 10 gallons of epoxy.

Using Denatured Alcohol

This is usually recommended over acetone or any other solvents. Denatured alcohol is effective in thinning epoxy because it does not affect the physical properties of the substance. When using denatured alcohol, the general rule of thumb is at least 20% of the denatured alcohol should be added to the epoxy.

Frequently Asked Questions

Is There Another Way of Heating Epoxy Besides Heating the Components Separately?

Yes, you can also thin your epoxy resin by heating the substrate for example wood, then apply your cooled resin and hardener to the heated surface.

What Happens if I Overheat my Epoxy?

Overheating hardens the epoxy quite fast and this might damage the epoxy. If you happen to notice any smoke, then probably your epoxy has been damaged, and you should replace it with precaution.

Why is a Solvent not Recommended When Thinning Epoxy?

There are a lot of disadvantages when it comes to using a solvent in the process of thinning epoxy resin. This is because the solvent can weaken the epoxy, it can cause the epoxy to shrink, and so on.

It is not always necessary to make epoxy thinner. But if you have to, the heating method is the preferable method as it does not reduce the qualities of epoxy. While you are at it, remember not to overheat as this might damage the epoxy resin. Adding solvents reduces some favorable qualities of cured epoxy such a strength, moisture resistance, and so on. However, the process of adding solvents is quick, and it’s a simple method of thinning epoxy.