When we are painting homes in Roland Park or Mt. Washington, we often have to repair hairline cracks in the plaster before any painting can be done.
The cracks in the plaster actually need to be widened before patching compound can be used. Use the sharp end of a 5 in 1 tool (or similar tool) to make a “V” sharpened tunnel, approximately 1/4″ to 1/2″ where the cracks are located.
After this is done use a dust brush first then a damp rag to remove any dust or loose plaster pieces. At this point it is important to use Durabond or a similar type product that has a bonding agent.
Skimcoat the compound on as smooth as possible while still making sure compound fills cracks completely.
Plaster homes in Baltimore require a specialist who is familiar with plaster repair. The biggest mistake is a well meaning painter treating plaster like drywall and using Fibertape or a similar material.