We use a putty knife and a 4" plaster knife. the trick is to add as little as possible and simply try to feather the edges so there isn't an abrupt change. Once the plaster (drywall mud) is dry sand it so it's smooth.anti wrote:So even what I see in pics 3 and 4 is plaster? It looked like wood from the picture!!
1.) How do you skimcoat something so uneven as your molding? Anto
We are useing a high quality latex paint but first we use spray oil primer in trouble spots and regular brush on / roll on primer in other large areas of fresh plaster.anti wrote: Is there a specific reason why you are using oil based paint? (I assume you are, since you're using oil based primer....) Anto
IAnto[/quote] Can the same treatment be used to fix plaster where the paint is cracking and breaking off or does plaster not stick on paint? Should a filling primer like XIM Peel Bond be used there?
XIM is a is an exceptional one on hard to stick surfaces or you can use Zinsser White Tintable B-I-N Shellac Base Primer. We used Kilz
Our walls and probably most plaster walls from this period were originally painted with a thick layer of Calcimine. What you are seeing in pic 3 and 4 is the layer of calcimine and some pigment residue. Pigment looks like wood in this case and the calcimine looks like 30 layers of paint. Most places it has held and is stable but in a few places it has failed.
Calcimine is an old, chalk and water based paint. New plaster walls are supposed to cure for up to a year before they are painted, but calcimine can be used right away. Often, people would build a house, plaster the walls, wait a few weeks and then throw on some calcimine. After some time, they could wash off the calcimine or paint over it, when the plaster had fully cured.
The problem is that as the calcimine ages, the binding agent in the “paint” starts to fail, and if any water or moisture gets between the calcimine and the plaster, it starts to release. If someone paints with latex paint, the water in the latex paint penetrates to the calcimine, and then the paint starts falling off on its own. It's almost impossible to paint over calcimine with latex. So we use oil primer to "fix" the edges of the cracked off area. We used a spray so as not to put any additional pressure on the calcimine. After the primer is dry we make plaster repairs and then we paint with a high quality latex paint.
Here is an excellent article that goes into great depth on how to deal with calcimine ceilings.
I hope this helps, Dan (Banner)