Do I need to size?
Technically we should say yes. But often the answer is project based. Surfaces may need to be sized if they are especially absorbent such as new plaster.
Our friends at Anaglypta have a wee test they recommend:
"We always recommend that walls are sized (where necessary) you can check to see if you need to size, by flicking water onto the wall surface. If the water runs down your wall, there is no need to size; however, if the water soaks in then sizing is necessary. There are many sizes available on the market, and we would recommend that you follow the manufacturer’s instructions very carefully".
So what is size?
Traditionally, size is a glue-based liquid. Its main function is to prevent plaster from sucking the moisture straight out the wallpaper paste. (If paper dries too quickly, or unevenly you get bubbles and stretches and creases.)
There are two types of size and many different brands:
Granulated (or powder) size: recommended under non-woven (‘Paste the Wall’) wallpapers. Wallpaper can be hung as soon as it is dry.
Latex size: recommended under paper backed (‘non-pasted’ or ‘pre-pasted’) wallpapers. Needs 2 hours to cure before wallpaper can be hung.
Both sizes contain ingredients to prepare your wall and prevent mould (although most pastes nowadays also have antimould properties), but also have many other advantages:
- Gives a longer wet life of the product, so the product stays workable longer
- Gives more slip and slide, so makes it easier to position during hanging
- Holds down the seams
- Helps prevent seams/joins opening
- Adds to the adhesion of wallpaper to the wall
- Makes it easier to remove the wallpaper when time comes to redecorate
- Protects the wall surface during the stripping process
Some wallpaper pastes double as size so check the back of your paste before buying size to see if yours is a 'two in one' product.
If in doubt - size.