What is PVA?
What is PVA glue made from? Our first port of call is 'Wikipedia'. Here is what they say about PVA:
"PVA is a rubbery synthetic polymer with the formula (C4H6O2)n. It belongs to the polyvinyl ester family and has the general formula [RCOOCHCH2]. It is a type of thermoplastic. Polyvinyl acetate is a component of a widely used adhesive, commonly referred to as wood glue, white glue, carpenter's glue, school glue, Elmer's glue (in the US), or PVA glue."
Facts about PVA glue
Polyvinyl acetate, the main chemical component of PVA, was discovered in 1912 by the German Fritz Klatte. The resulting glue does not develop any odors or dangerous fumes and can be touched with bare hands without hesitation.
It can be used not only for "real" wood, but also for plywood, chipboard and MDF boards. It can be used as a heavy duty sealer, primer, binder and dustproofing agent.
PVA cures with good air circulation and dries fastest at room temperature. You get the strongest seal when you clamp the parts to be bonded. It dries quickly and has a very high adhesive strength.
PVA is flexible, permanent and only toxic if you eat it. It has a neutral pH.
PVA is water soluble. You can add water yourself to thick glue to make a thinner, less gooey glue. It's best to add a small amount of water to the glue at a time (not the other way around) and give it a good stir so you don't dilute it too much.
Using PVA glue
What is PVA glue used for? As a water-soluble emulsion, it is particularly suitable for bonding porous materials, especially wood, paper and fabric. It contains no solvents and is a useful consolidating agent for porous building materials such as sandstone. PVA glue is flexible, provides a very strong bond and, unlike many polymers, is non-acidic. PVA wood glue is most commonly used:
- as wood glue
- as an adhesive for paper, fabric and leather
- in the bookbindery
- in handicrafts, for example for mosaics
- as glue for envelopes
- as wallpaper glue
- as a primer for drywall
- as a filler by adding sawdust to it
A 50/50 mixture of PVA and water is a very good sealant for plaster of paris in preparation for painting or wallpapering. It can also be used as a non-waterproof interior varnish, perfect for paper mache projects.
7 steps to using PVA to glue wood
PVA is an inexpensive, non-toxic, water-based method of gluing wood. Wood glue is an extra strong version of ordinary PVA, ideal for heavier jobs. It dries completely clear, but you can also buy pre-colored (white/yellow) versions that are less visible on wooden surfaces.
- Press the glue onto the surface of the two pieces of wood you want to glue together.
- Immediately wipe away any excess or spilled glue with a damp cloth.
- Use either a special plastic spatula or a brush to apply a thin layer of glue to the surface of the two pieces of wood.
- Press the pieces together and rub the surfaces from side to side to remove trapped air and ensure the glue is evenly distributed.
- Take a clamp or two and clamp the parts.
- Allow the parts to sit for 24 hours before removing the clamps.
- Sand off excess dried glue.
The disadvantages of PVA glue
- Various fungi, algae, yeast, lichen and bacteria can decompose and degrade polyvinyl acetate.
- PVA must not be allowed to freeze, as this will degrade the polymer, rendering the glue useless.
- You can't paint PVA, but you can paint over it
- It takes 24 hours for the connection to reach full strength. (There are wood glues that dry faster)
- It is not fully waterproof except for D4 glues