Spider cracks have appeared on ceiling after painting

Did you wash the ceiling with fresh water after using sugar soap? This can sometimes affect the behaviour of some paints. Another reason (more probable) is, did you allow and follow the recomended drying times for each layer of paint you applied? If not, spider cracks can appear because of the paint drying at different rates. And my only other suggestion, is that the undercoat/primer or stain sealer was applied too heavy? I hope this helps =D

Unfortunately 'D' has touched on it. I don't use sugar soap on absorbent surfaces for this very reason. Sugar soap is a fabulous product for washing down woodwork and PVC. As long as you rinse down completely. This can not be done with walls and ceilings because of absorbency. As soon as you apply another wet product~paint, the sugar soap residue since hiding in the plaster work reconstitutes and bleeds through the paint. Spidey ceiling. Undercoat the ceiling is the cheaper solution, and reliable. But undercoat all the ceiling. Ben