What should I do to the wall before painting?

Generally, when decorating a new wall, you don't need much preparation work, but you should test the alkalinity and moisture content. The moisture content of the wall can be tested by a moisture content tester; You can use ph test paper to measure the ph value-first wet the test paper with distilled water and stick it on the base surface to be measured, and you can know the alkalinity of the wall according to its discoloration degree. However, if you find tiny white powder on the wall, it means that the wall contains salt and should be clean. After the cement wall is dry and light-colored, use sandpaper to smooth the wall and paint it. If there is too much white powder on the cement surface and it is continuously leached. Please brush a layer of primer after cleaning to prevent salt from eroding the wall in the future.

Treatment of painted walls:

Please wipe with sponge or rag first, clean the ceiling first, and then clean the surrounding walls. If you wipe it with water, remember to wait until the surface is completely dry before sweeping the paint. If the surface of the old paint is smooth, it must be rubbed gently with sandpaper to strengthen the adhesion of the new paint film.

In addition, also need to pay attention to:

Remove peeling paint film:

Remove the peeling paint film with scraper or iron brush, and then polish the smooth surface with sandpaper.

Remove pasted wallpaper:

Be sure to remove the old wallpaper. You can mix detergent with hot water, soak the old wallpaper thoroughly, scrape the paper clean with a scraper, clean the residual glue on the wall with clear water, and polish it smooth with sandpaper after drying.

Surface finishing:

Fill the gap in the concave hole with a batch of earth knives, and smooth it with sandpaper pad after it is completely dried.