Is it ok to put shellac over acrylic paint?
Yes the shellac has been used decoratively for generations admittedly mostly on furniture where it is integral in French Polishing which still looks good hundreds of year later often darkening and mellowing. I believe it was used to seal the plaster on gilt picture frames and furniture too before they were gilt. I have used shellac on very dry plaster (damp or moist plaster will causes blisters as trapped water affected by the seasons ) with acrylic paint and the more coats of shellac the more intense the colour instant old and it still looks the same 20 years later! Lightly rub with methylated spirits soaked steel wool to smooth the surface between them. Besides it is almost 100% removable with same spirits so goof proof repairable enjoy the exploration and expression. Try adding spirit based inks or pigments even furniture stains to either the plaster or shellac for extra depth and wash effects.
