Just like paint, there are also different types of wood glue. Some are suitable for indoors and others for outdoors. There are also quick-drying glues and glues with a longer drying time. Here we will give you an overview of what you need to look out for when buying and using wood glue.
Moisture resistance
The first characteristic of wood glue is the degree of resistance to moisture. The European Standard NBN EN 204 distributes glue in 4 different classes, which you can also find on the packaging.
D1: non moisture-resistant glue
For indoor use, for example furniture.
D2: moisture-resistant glue
For indoor use and also in bathrooms or kitchens with adequate ventilation.
D3: water-resistant glue
For indoor use in bathrooms and kitchens. Also suitable for outdoor use if the wood and glue is well protected.
D4: waterproof glue
For indoor and outdoor use. This glue can handle long-lasting and regular periods of moisture. It is ideal for outdoor furniture or for wood that is constantly in contact with water, such as piers or boats.
Important: When you use a type of wood glue with a low moisture resistance, you run the risk that the adhesive loosens after a while.
Composition of wood glue
Looking at the composition of the glue, we can distinguish different types. The best known are the PVAc wood glue, the PU glue and Epoxy glue.
PVAc wood glue
This is the well-known white wood glue that dries colourless. The glue settles in the wood through absorption into water, creating a strong adhesion. Both parts need to connect well because it is a dispersion glue – a glue in which the glue particles are evenly distributed as a liquid. PVAc (“polyvinyl acetate”) wood glue is thus not suitable for filling of gaps or for glueing uneven surfaces. At Klium you’ll find a wide range of PVAc wood glue brands, for example Rectavit.
PU, of polyurethane wood glue
This type of wood glue has a similar strength as PVAc wood glue, but the use and the colour are different. The brown colour can leave ugly spots on your wood, so please make sure to be careful when using it. The PU glues are available as single component and two-component: the two-components glue has a second element added to accelerate hardening. This makes it possible to apply a thicker layer of glue and to apply it on larger surfaces. PU glue reacts with the moisture in the air: it foams and then hardens. This also explains the other name that is often used for this glue: foam glue. The foam ensures that splits, cracks and uneven surfaces are filled. Both parts that are to be glued must be clamped properly, so that the foam remains in place while drying. This moisture-resistant glue is available from brands like Soudal or Rectavit.
Epoxy or resin glue
Epoxy glue is harmful to the skin, therefore many people don’t like using it. Before use it should be mixed. Epoxy glue is actually also a two-component epoxy glue. This glue is very strong and is also an ideal filler because it is a liquid and dries rapidly.
Special wood glues
- In addition, there are some lesser known wood glues such as rabbit skin glue or hide glue. This glue is made of the skin and ground bones of small rodents like rabbits or hares. Hide glue should be applied while hot. This makes the glue difficult to use, though it is very elastic and can be applied in very thin layers. The glue loosens upon reheating. Typical examples for the use of hide glue are the construction of musical instruments and veneer work.
- A glue that is seldom used nowadays is casein glue or cold glue, the forerunner of PVAc glue. This was originally created by pulling casein – a protein – from milk. Nowadays the glue comes in powder form and is mainly used for (surface) painting. The glue is strong, elastic and has the added advantage that it does not need to be processed quickly.
