How do I fix bubbles and blisters in wallpaper?

Wallpaper expands when it is pasted and contracts as it dries. A great deal of what looks like a defect on the day of hanging is simply paper that has not finished shrinking back.

What you'll need

• A sharp craft knife or a scalpel
• A glue syringe or a fine artist's brush
• Wallpaper paste or overlap adhesive
• A seam roller
• A damp sponge

Step by step

1. Wait before doing anything.Give freshly hung paper 48 hours. Most bubbles are excess moisture and they close up as the paper dries and tightens onto the wall.
2. Assess what is left.A bubble still present after the paper is fully dry is an area with no paste behind it, or a hollow in the wall, or something trapped underneath.
3. Feel for a lump.A bubble with a hard point in the middle is a lump of dried paste, a piece of grit or a nib on the wall. Slitting it and pressing will not work until that is removed.
4. Cut with the pattern.A single slit with a very sharp blade, along a pattern line or in the direction of the paper's grain. On a plain paper, a small X or a cut along the natural fall of the light.
5. Use a fresh blade.A scalpel or a new snap-off blade. A dull blade tears the paper and the repair is then visible whatever else you do.
6. Inject paste through the slit.A glue syringe is the neat way. Otherwise work a little paste in with a fine brush through the cut, spreading it under the whole bubble.
7. Use the right adhesive.Ordinary wallpaper paste for most papers; an overlap or repair adhesive for vinyls and heavy papers, which standard paste will not hold.
8. Work the air out.Press gently from the edge of the bubble towards the slit so the air and excess paste come out of the cut rather than being trapped.
9. Roll it flat.A seam roller over the repair, then wipe the excess paste off immediately with a damp sponge. Dried paste on the face of the paper leaves a shiny mark.
10. Do not roll embossed or textured paper.It crushes the texture permanently. Press with a sponge or a soft cloth instead.
11. Deal with a hollow wall.If the bubble is over a genuine dip in the plaster, no amount of paste will pull the paper into it. The wall needs filling, which means taking that drop off.

Tips

• A glue syringe costs very little and is the difference between an invisible repair and a smeared one. Every decorator has one.
• Bubbles that appear in a straight line usually follow a ridge or a joint in the wall underneath. That is a preparation problem, not a hanging problem.
• Hang paper from the centre outwards with a smoothing brush and most bubbles never form in the first place.

Common mistakes

• Attacking bubbles on the day of hanging — Wet paper is expanded and slack, and much of that slack disappears as it dries and shrinks onto the wall. Cutting and pasting bubbles that would have vanished leaves permanent slits in the paper for no reason.
• Using a blunt blade — Wallpaper is a thin, layered material. A dull blade tears rather than slices, so the edges of the cut lift and fluff. That is visible even after the repair is pressed flat, and no amount of paste hides it.

If it doesn't work

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