We recommend using Plaster primer 301 for strongly or irregularly absorptive substrates. A quick test which can be done to see if the plaster is absorbent is, spray a small amount of water onto the surface and see if it is absorbed quickly, if it is, this primer should be used.
Alternatively, new plaster can be primed by thinning out the first coat of white paint (321, 524, 331) with 10% water.
The Grip coat primer 505 is suited for weakly absorptive and irregular substrates.
We do not recommend painting a colour directly onto new plaster, it should be primed with a coat of white or plaster primer to give it a stable surface to be painted. If it is not primed this way the colour could look patchy due to differently absorbing areas.