I have recently hired someone to create a venetian plaster ceiling for me. I am new to VP and have noticed hairline cracks in parts of the ceiling and was told that they are normal to the process. The installer was highly recommended and has a strong portfolio. Is cracking normal?

cracks happen when plaster dries too fast and/or applied to thick, building movements (whatever the reason may be).

and yes they do happen in base layers and could "pop" in the final one here-and-there but to the "certain extend"...

so if you have 1 or 2 small hairline cracks on 20X20 ceiling it is fine...