1. Use SafeMend™
There are several ways to repair hairline cracks, but using a wall mending agent is by far your best option. SafeMend™ is a toxic-free wall mending agent that is used for filling in wall cracks. Alternative products contain harmful chemicals that can harm people and pets. Fortunately, SafeMend™ is non-toxic and 100% safe.
2. Have the right tools
You don’t need many tools when repairing a hairline crack, but having the right ones can make your job a lot easier. If you’re repairing a plaster wall, you may need to use sandpaper to roughen the surface, allowing the mending agent to stick better. Sanding the surface also helps when painting over the mending agent, providing a smoother finish.
3. Clean the surface
When repairing hairline cracks in concrete, it’s vital to clean any dirt and debris from the surface first. A clean surface ensures the mending agent bonds perfectly to the wall. Pressure washing is a great way for cleaning concrete walls prior to repairing and painting them.
It's not the best idea to go blasting a pressure washer indoors. So, if you have to repair interior walls, you can simply use a vacuum or cloth.
4.Widen the crack
As ridiculous as it sounds, making the crack larger is a great idea if you are having trouble getting your mending agent to stick. In hairline cracks, there is not much surface area for the agent to be applied to. By widening the crack, you allow more of the mending agent to seep in.
Be sure to clean any excess debris or dried paint from the crack, as it can affect the mending agent's ability to bond.
5. Prepare for painting
Having a colorful feature wall in your home can be completely ruined by a hairline crack. If you do have a colorful wall, a paint job will most likely be required. A poor paint job can sometimes look worse than the crack itself, so it’s important to prepare before painting.
Once your applied mending agent has dried, you should sand down the surface to make it nice and smooth. Painting over an even surface makes it easier to blend in with the rest of the wall. If you’re applying two coats of paint, then it is important to allow enough time for the first coat to dry.