How to Thin Wood Glue That Has Thickened

In the woodworking world, wood glue is a huge and popular help. The useful adhesive has one big downfall, though: it can thicken, making it harder to use or even useless. While wood glue is common and can be found in most stores, it can be a pain to replace and buy often.

Because wood glue thickens, the flip side has also been asked: how can you thin wood glue that has been thickened? Depending on the type of wood glue, there are about four main ways to thin wood glue that has been thickened. You can tap the container on a hard surface, add water, add some drops of vinegar, and even heat the container in a pan of warm water.

Seems pretty simple, right? While it does seem simple, there are still important things to know about wood glue before just going right out and trying to thin it.

To make sure you’re prepared with everything you need to know about thinning wood glue that has been thickened, we’ll let you know all the basics on wood glue, like the types of wood glue there are, why wood glue thickens, how to prevent it from thickening, and of course how to thin it back out!

The Basics of Wood Glue: What You Need to Know

Before diving into how wood glue gets thickened, how to prevent it from thickening, and ways to thin it once it’s become thickened, there are some basics about wood glue that you’ll need to know. There are a few different types of wood glue that each have a variety of uses.

The type of wood glue being used can determine how long it will last before becoming thickened and can also determine the method you’ll need to use to thin it back out. First things first, let’s discuss the different types of wood glue and their uses, then take a look at how to prevent wood glue from thickening in the first place.

What is Wood Glue?

To keep it simple, wood glue is a type of adhesive that is specially engineered to be used on wood. Wood glues form tight, durable bonds between pieces of wood and they’re extremely common in the worlds of woodworking and repair.

Like with most products, there are several different types of wood glue.

The Five Main Types of Wood Glue

There are five main types of wood glue that are commonly used for woodworking projects and repairs everywhere. They have different uses and different properties, and it’s helpful to know about them!

PVA Glue

“PVA” stands for polyvinyl acetate – the ingredients in this type of wood glue. Polyvinyl acetate essentially just means this type of glue is often odorless and colorless. PVA glues are the most common type of wood glue, and most glues you see around people’s homes tend to be PVA glues.

PVA glues can be non-waterproof and waterproof and have a wide variety of uses. They’re great because they’re available virtually anywhere and they’re fairly easy to use.

The downside of PVA glue is that they can actually affect finishes on wood if excess glue isn’t removed – to the point that the finish no longer looks good. When working with PVA glue, it’s important to remove any excess glue to keep finishes looking the way they were intended.

Polyurethane Glue

Polyurethane wood glues are activated by moisture. They have some great properties; polyurethane glues are waterproof, dry quickly, and dry hard. They can be used for a lot of projects because they can be used both indoors and outdoors.

The downside of polyurethane glue is that like PVA glue; it can have bad effects on wood finishes. This type of glue also needs to have any excess removed to protect wood finishings.

Two-Part Epoxy Glue

Two-part epoxy wood glues are called two-part because, well, they’re made up of two parts: a resin and a hardener. These two parts on their own don’t make use for glue, but once they’re combined, they create a chemical reaction resulting in a waterproof glue that is great for filling cracks, dents or holes in wood, unlike other types of wood glue.

Hide Glue

Hide glue is like its name implies: it’s made from animal hides. There are two types of hiding glues; the first type is hot hide glue, and the second type is liquid hide glue. Liquid hide glue tends to be more popular for woodworking projects and it has one standout benefit: it doesn’t affect wood finishes like PVA glue or polyurethane glue!

Be aware, though: hide glues may need a little longer to dry than other types of wood glues.

CA Glue

CA wood glue, which stands for cyanoacrylate glue, is used to bind hard pieces together in woodworking. It cures and dries very quickly, and accelerants can even be added to make the application process faster.

What Makes Wood Glue Thicken and How to Prevent It

Now that you know about what wood glue is and about the different types of wood glue there are, it’ll make much more sense to find out what can make wood glue thicken and how you can prevent it.

What Can Make Wood Glue Thicken?

Perhaps the biggest factor in wood glue thickening is improper storage. Wood glue technically has a shelf life of one to two years, but it’s notorious for lasting and staying usable without thinning for much longer than that.

Wood glue is only known to withstand about five freeze and thaw cycles – very fluctuating temperatures can also make it thicken more easily. Excessive heat can also make wood glue thicken, as can exposure to a lot of air.

Ways to Prevent Wood Glue from Thickening

The good news is, there are a lot of easy tips to keep wood glue from thickening! Here are some tips to prevent your wood glue from thickening:

  • Squeeze out excess air from the bottle before sealing if you can
  • Keep the bottle tightly sealed
  • Store the bottle in your refrigerator if you have room
  • Put your wood glue in an insulated lunch pack if you live somewhere with freeze/thaw cycles and plan on keeping it outside
  • Keep your wood glue somewhere that the temperature stays pretty constant, and isn’t prone to excessive heat or cold

Can Wood Glue be Thinned?

With all the talk about wood glue thickening, you probably think the opposite can happen – can wood glue be thinned? Absolutely! There are some different methods when it comes to thinning wood glue, and different types of wood glue may call for a different method of thinning.

Materials Needed to Thin Wood Glue That Has Thickened

If your wood glue has thickened and you’re hoping to thin it back out, you’re in luck! It’s fairly easy to do. There are a few materials you might need – it all depends on the method you want to use to thin your wood glue. In different cases, to thin your thickened wood glue, you may need:

  • Water
  • A pan
  • Vinegar
  • A hard surface

Methods of Thinning Wood Glue That Has Thickened

Like mentioned previously, there are several different methods to thinning wood glue. Let’s take a look at them.

Method One: Tap the Container on a Hard Surface

A popular and proven first step to take when trying to thin wood glue is to tap the container on a hard surface. Do this repeatedly to loosen up the contents of the wood glue container. If you’ve done this a few times and your wood glue isn’t thinned out, you can move on to other methods.

Method Two: Add Water

“Just add water” is a popular method for a ton of things – including thinning wood glue. According to Titebond, water-based wood glues like polyurethane glues can be thinned by adding water up to 5% of the weight or volume of the glue.

Titebond highlights that it’s important to not add more than 5% of the weight or volume of the glue in water – this can decrease the bond strength and effectiveness.

Method Three: Add Vinegar

A lot of people thought this method for thinning wood glue was an old wives’ tale, but it turns out it works – and it works well! Adding a drop or two of vinegar to your wood glue and mixing it can revive thickened wood glue.

Method Four: Heat It Up in Warm Water

You read that excessive heat can actually make wood glue thicken more – so to make it clear, this method only applies to liquid hide glue! Liquid hide glue can be thinned by gently heating the container or bottle up in a pan of warm (not hot!) water.

Place the container in the warm water and check it periodically to see if the wood glue is thinning. It may take a minute or two for results to start showing up.

How to Know When to Get Rid of Wood Glue

While wood glue that has thickened can be thinned back out, there’s still a point when it’s time to throw that container of wood glue away and get a new one.

You should get rid of your wood glue if:

  • Its color becomes orange-colored or orange-tinted
  • It becomes so thick it won’t thin out or run at all
  • It becomes stringy
  • It doesn’t attach to the wood at all when applied
  • A foam or skin has formed on top
  • Its consistency is like a gel (usually orange in color)
  • It looks separated, much like oil sitting on top of a solid
  • It becomes lumpy

Ready to revive and thin your wood glue that has thickened? Now you know how!


I've been building things for many years, and I want to share what I've learned to try and help whoever I can. Make sure to checkout the homepage for my most read posts!

Recent Posts