Bubbles can appear for varying reasons:
1. Base surface
· The base surface is too absorbent (ie. gypsum plaster board.) Since the paste may soak too quickly into the wall in places, the wallpaper on these places may loosen and create bubbles.
Absorbency can be reduced by using a solvent-free primer.
· The base surface is clogged. This can occur when too much primer has been applied, which may be evidenced by a greasy appearance on the base surface following priming. Water can then bead on the walls. Since a closed layer has been formed on the wall, the paste cannot adhere to the wall. Therefore, this layer must sanded away using either sandpaper or a polisher
· The base surface is too coarse
· The base surface is not stable
2. Soaking time
· It is necessary for paper wallcoverings to soak, because paper is made of wood fibres, which swell when in contact with moisture (paste.) This causes the wallpaper to become wider and longer. If the wallpaper is not allowed to soak for the recommended amount of time, the wallpaper will stretch when hung on the wall, which causes bubbles.
3. Paste
· Incorrect paste
· Paste is too thin, as a result of mixing too much water
· Layer of paste is applied too thinly
· Layer of paste is applied to thickly
· Additional paste applied to wall before hanging wallpaper strip (in the case of paper wallcoverings)
4. Other reasons
· High humidity, due to closed windows and doors
· Low temperatures (at temperatures lower 10 °C, the wallpaper dries too slowly).
What causes bubbles, and how can they be avoided?