Plaster on old plaster with remnants of tile adhesive?

[Jensab]

I'm renovating the basement and going to plaster the lightweight concrete blocks with plaster mix C. However, about 4 square meters of the blocks are covered with old plaster with some remnants of tile adhesive left... I have scraped off everything loose, but I'm wondering if I need to remove ALL the adhesive? Or is it enough to remove the worst of it? Should I use primer on that surface? Does anyone know? Grateful for answers.

 

[Helioz]

No, if you have scraped away all loose material, roughened up, and cleaned the surfaces, it's not a problem to apply plaster. If you are going to paint with a diffusion-open paint like lime paint or silicate paint and have a lot of moisture, you can apply rödgrunda to the wall to create a bit more protection, even out the absorption so that the lecafogar aren't visible, and maximize the adhesion of the plaster.