What are the different types/grades of wood glue?

Question

I was wondering what where different types or grades of glue there is for gluing wood. I use titebond and there is others. My Question is simple. Can somebody list the different types and how the benefit over the others. Like maybe titebond is the type and this other brand is a different type. Hope you guys know what I mean with my question, thanks!!

Answer 1

This is really too broad for SE but at some point there was going to be a question that asked about wood glue generally and I think it makes a good reference point for future visitors so I'm going to try to answer it. But be aware that despite how long this is it's only a brief overview of the subject and not at all comprehensive.

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Some previous Q&As covered quite a bit of the ground here so I think I should link to all of them I could find to start with, for cross-referencing:
What is special about wood glue?
What are the applications for polyurethane glue?
What is the appropriate wood glue for outdoor wood furniture?
What type(s) of glue can I use on wooden kitchen utensils and devices?

It's perhaps not that important but I think it's worth mentioning that while there are glues sold to bond wood the reality is that few were actually developed specifically for wood. Instead we use glue that has been packaged/sold for use by woodworking trades. Where this is of interest is in deciding on an adhesive not sold specifically to woodworkers for certain special applications. Probably the best example of this is the early experimenters who tried cyanoacrylate adhesives (CA, superglue) and found them useful for a few specialist jobs.

If I try to list all the glues used in woodworking I'm sure to miss out a few, and the list would be overly long anyway, so this is just a few key ones. As for listing the various strengths, weaknesses and ideal applications for all of these that is definitely beyond the scope of SE so I'm not going to attempt that but I'll touch on a few interesting points.

Casein
AKA milk glue or milk-protein glue. No longer widely used but a very important adhesive in its day. Can be made at home fairly easily if anyone wants to experiment with it in a small way, but it's still possible to buy this and the quality and consistency would be better.

When you make it at home you produce a wet paste, the commercial version comes as a dry powder that you mix as needed into a paste with water. It doesn't keep very long, even in the refrigerator, so don't make or mix too much.

Hide glue
Hide glue is not one thing, it is many closely related products, part of a broader class of protein glues derived primarily from animal skins.

This and fish glue used to be the wood glues, and for many centuries were almost the only adhesives used in furniture making. In the past it was a hot glue (often referred to in English sources as "Scotch glue") and had to be kept warm for use in a double boiler, and the wood surfaces usually warmed prior to application as well.

You have to be very careful not to overheat the original form as that spoiled the glue, which along with the sometimes rank smell of the old glue pots made using it not particularly pleasant. Today we have room-temperature versions such as Old Brown Glue and Titebond's Liquid Hide Glue that make it a lot more user-friendly, at the cost of a little of its strength (still plenty strong enough though). Unlike many glues hide glue joints are reversible, using moisture and heat, making them very popular still with instrument makers for example.

Fish glue
Derived from the skins or swim bladders of certain species of fish, e.g. sturgeon. Originally a very important adhesive (not just to woodworkers, it was widely used in other crafts) and while not commonly used today still valued for certain specialist applications.

Starch
Starch glues are well worth experimenting with particularly with children because you can turn an everyday food product (flour, starch, rice) into something that will glue. Starch glues can be quite strong, good enough for smaller items but they don't usually form bonds that you'd rely on for furniture work.

PVA
You could probably devote a chapter of a book on these alone. As you can see from some of the information in the above links there are a few types. The main class difference might seem to be between the white and yellow forms but they're broadly similar.

In reality the main thing that separates PVAs into two nearly distinct categories of glue is whether it is water-resistant or not, and it is not just the yellow form that can be water-resistant or waterproof.

PVAs of all types are the most important woodworking glues in the modern era, and their relative cheapness, ease of application, lack of a strong odour, easy cleanup with water and other advantages ensures they'll remain popular.

Epoxy
Obviously there are many different types of epoxy, almost everyone is familiar with there being fast-setting types (3-min, 5-min or quick-set epoxy) and slow setting types with 'drying' times of an hour or more but it goes much deeper than that.

As a general rule the slower the setting time the stronger the epoxy.

Where gap-filling is important epoxy is the glue of choice and it can/should be filled with wood flour or fine sanding dust when used to fill major gaps.

Note: epoxy is one of the few glues that doesn't require clamping pressure to achieve a strong bond.

Polyurethane
We're probably most familiar with the foaming type (the original Gorilla glue being the classic example) but there are actually a number of classes of polyurethane glue, including types that are a paste consistency, e.g. "construction adhesive".

The foaming quality of the usual type used by woodworkers has led to the belief that it can fill gaps, and it does — with a weak foam that has little strength. Polyurethane requires good clamp pressure to ensure a good bond, and it's important to watch out for the foaming pushing a joint apart with the pressure created.

Urea-formaldehyde
Extremely important industrially (for most of the 20th century this was the glue used in plywood manufacture) and in some production woodworking shops, not widely use by home woodworkers. Can gap-fill to a small degree but it shouldn't be relied on for this. It and some closely related glues create coloured glue lines, which obviously limit where they can be used.

Superglue
Generally what's known as "superglue" is cyanoacrylate. Also used as a finish, most commonly among pen turners I think.

There are actually a few versions of this glue (not just liquid and gel types) with a broader range of properties than you might suppose. This is not used as a general-purpose glue in woodworking in that you would not use it e.g. to glue a large joint together, but it does have some uses, mainly for small repairs and/or in non-loaded applications. Superglue can cure very quickly, and even more so when used with a chemical "activator" which usually comes in an aerosol spray can. Woodturners in particular sometimes use superglue to repair smaller/very fine grain splits, and it can also be of use to bond small mitre joints such as on picture frames.

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IMPORTANT NOTE
It should be noted here that many glues sold to woodworkers tout their strength (including the now-infamous old marketing tagline for Gorilla glue). And there are various adhesive test published in magazines and done by various woodworkers online that do show that there is a range of joint strengths produced. But this can obscure the fact that the weakest of them is generally capable of producing joints strong enough for use, and the least expensive PVA can make joints as strong, or stronger, than the wood around them.

Once you match or exceed the strength of the wood itself you've done all you need to, any stronger than that is interesting but unimportant.

Answer 2

A while back I was also scratching my head over this same question/issue.

I just wanted to know the different types of wood glue I could use for my woodworking projects at home, as well as where to apply them.

After thorough research consulting several woodworking/adhesive sites, and also visiting my local hardware shop, I learnt that when it comes to wood glue, one type does not fit all woodworking applications.

Most of us are familiar with the yellow wood glue or Titebond which is actually a brand of Polyvinyl Acetate (PVA) glue. All your yellow and white wood glue are all PVA glues, which is just one of the types of wood glue (though it is the most common).

Michael Pekovich of Fine Woodworking says that it is great for about 80 percent of your woodworking projects. Considering how common it is, I'm sure he's right.

There are other types of wood glue and I figured it wouldn't be a bad idea to make an infographic about this topic that makes everything easier to read and comprehend.

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