White Glue - The Classic in Workshop Applications
White glues are a classic in workshop applications. Still, there are a few things to bear in mind. Did you know that contact with iron can lead to blue discolouration in the wood? Or that the open time of the glue depends on the surrounding temperature? A reoccurring, contentious issue is the content of formaldehyde in the products. Therefore, we also have in our range products low in formaldehyde.
White glue is based on polyvinyl acetate as a binder and is therefore also known as PVAc glue. The thermoplastic dispersion glue is used for bonding soft and hard woods, for HPL surface face bonding, for gluing board gaps, for block bonding and carcass and assembly applications.
These water-based wood glues harden physically by drying out. The water evaporates from the glue line and/or is absorbed by the workpieces. White glues are needed for different purposes in the workshop, as for example HPL surface bonding, solid wood, block or assembly gluing. High final bond strengths are achieved. The addition of hardeners boosts the adhesive properties of white glues. We supply glues and hardeners from various manufacturers to cover various applications. Our white glue REDOCOL Kombicoll Super-N is available with a practical Comfortable and easy operation
Durability Groups for Wood Glue: D1 to D4
One of the most important classifications for white glues is the durability group as per EN 204. It gives information on the water resistance of the adhesive and allows conclusions on when it might be adviseable to change to other adhesive systems (e.g. PUR).
D1: Interior Doors, Furniture and Claddings
Dowel processing, max. wood moisture 15%.
D2: Living Room and Office Furniture
Influence of running water or condensation and/or occasional high air humidity and an increase of the wood moisture level up to 18 %.
D3: Kitchen, Bathroom Furniture and Stairs
Interior with frequent short-term exposure to running or condensed water and/or occasional high level of humidity.
D4: Exterior Applications: Windows, Exterior Doors, Stairs
Exposure to running or condensed water and/or occasional high level of humidity. Exterior exposed to weather, but with adequate protection by a suitable surface coating.
What can be done against bleed-through?
Many carpenters know bleed-through all too well - particularly when bonding veneer edgings. How may this phenomenon be avoided or at least reduced?
There are several possibilities. Firstly, it helps to reduce the pressure and make the glue mixture a little thicker. The amount applied is of importance. Normally, 90 to 100 g per m² suffice. For highly absorbent surfaces, 120 g per m² may be used.
You can draw conclusions from a simple finger test: if you are able to draw finger tracks into the glue, too much adhesive has been applied. Should the glue bleed through despite all caution, clean the surface immediately with warm water, a cloth or a scrubbing brush. The faster you react after the pressing, the better it will work.
White glues normally have a pH value between 3 and 5. They are thus graded as acidic, aqueous solutions. Due to the acidic pH value, discolourations of the wood may occur with certain wood types (e.g. oak), when processing white glues.
Therefore, it is advisable to execute test bonds beforehand. An alternative is the use of pH-neutral white glues. This will considerably reduce the risk of wood discolouring.
Viscosity - a Measure of How a Fluid Flows
The greater the viscosity, the thicker (lower flow rate) is the fluid, the lower the viscosity, the thinner (higher flow rate) is the fluid.
High viscosity – low flow rate -thick – e.g. honey
Low viscosity – high flow rate - thin – e.g. water
Pressing Time of Wood Glue
The pressing time is the time needed to reach the necessary minimum strength. The type of wood as well as the pressing temperature have an influence on the pressing time:
- a longer pressing time is needed for hard-textured wood as well as for resinous or oleaginous woods.
- you can reduce the minimum pressing time by increasing the pressing temperature
