Have I used the wrong paint?

The right answer to your question is: Zinsser All Coat multi surface primer and finish. On the old plaster in your situation you will have to use zinsser as the surface was not rub down probably and the primer is making a bad reaction with the shiny wallpaper glue. Hope is helpful

Its pretty common given the humidity and temperature fluctuations. Sometimes the psint doesn't adhere to the old plaster if the preparation is not done right.

Hi, can You say bit more what primer you have used ? It should be all right to send it a little bit and use a top coat.

Hi there, you haven't used the wrong material the small cracks are a result of poor adhesion due to lack of preparation. As the paint on your wall dries, it shrinks and small fine cracks or splits may occur if the paint's adhesion with the existing surface is not 100 percent effective. This can also be caused by heat or moisture but I would suggest that you sand the walls back and reapply once you have a solid base then proceed and finish decoration as once this is done you will have removed all the relevant posdible causes.

Hi this is Michael specialist in spray painting MDF wardrobes. It's possible that the primer you used on the old plaster wasn't the best choice for the job, which could be causing the tiny cracks to appear. Armstead primer for new plaster is designed to seal and prepare newly plastered surfaces for painting, but it may not be the best choice for a previously painted surface. To fix the issue, you'll need to remove the primer from the old plaster using sandpaper or a paint stripper. Once the old plaster is clean and free of primer, you can apply a primer designed for previously painted surfaces, such as Zinsser Bulls Eye 1-2-3. This will help to ensure that the paint adheres well to the old plaster and will minimize the risk of cracking. When painting, make sure to use a paint that is suitable for the surface you're painting on, and follow the manufacturer's instructions carefully. It's also a good idea to paint a small test area first to make sure the paint adheres properly and doesn't cause any issues. In summary, to fix the issue with the tiny cracks on the old plaster, you'll need to remove the existing primer, apply a primer designed for previously painted surfaces, and use a suitable paint for the surface you're painting on. It's important to follow the manufacturer's instructions carefully and to test a small area first to ensure the best results. Good luck with your decorating venture!