Wallpaper paste works by providing a strong, moisture-activated adhesive that allows wallpaper to bond securely to a wall surface. Here's a breakdown of the process:
1. Composition and Activation:
- Most wallpaper pastes consist of starch-based polymers (like modified potato or corn starch) or methylcellulose.
- These polymers are dry and inactive until mixed with water.
- Adding water causes the polymers to swell and hydrate, creating a viscous, glue-like substance.
2. Application to Wallpaper:
- The paste is applied evenly to the back of the wallpaper. This is crucial.
3. "Booking" (Soaking) Time:
- After pasting, the wallpaper is typically "booked." Booking involves folding the pasted sides of the wallpaper onto themselves, paste-to-paste.
- This booked state allows the moisture from the paste to evenly saturate and penetrate the wallpaper fibers. This pre-soaking step is vital.
4. Expansion and Preparation:
- The moisture from the paste causes the wallpaper to expand. Allowing the wallpaper to expand before hanging it on the wall is essential. This prevents bubbles from forming later as the paste dries and the paper shrinks on the wall. Without booking, the paper would expand after being applied to the wall, causing vertical bubbles.
5. Adhesion to the Wall:
- When the wallpaper is applied to the wall, the paste creates a bond between the wallpaper fibers and the wall surface.
- The paste's adhesive properties ensure that the wallpaper sticks firmly to the wall.
6. Drying and Curing:
- As the paste dries, the water evaporates, and the adhesive polymers form a strong, rigid bond between the wallpaper and the wall.
- This curing process provides long-lasting adhesion.
In essence, wallpaper paste acts as a go-between, using water to activate its adhesive properties and allowing the wallpaper to expand before it's hung. This process ensures a smooth, bubble-free finish.
