The Ceresit primers recommended for skim coat application are: Ceresit IN 10 and Ceresit CT 17 Profi.
For large areas that are skim coated with plaster, it's best to use an oil-based seal binder designed for porous surfaces like Dulux 1L PRECISION White Sealer Binder.
You have to prime new plaster before painting it. Freshly plastered walls are very dry and such the moisture out of your paint. Priming the walls with a mist coat first will ensure you end up with a great paint finish that doesn't flake or peel off.
Clean first, sand next to give the surface a ``tooth'', them skim coat and sand as many times as necessary to get the quality of finish desired, primer (PVA) and then top/color coat.
According to another paint forum, Sherwin Williams Loxon is the best primer to use for ``new'' real plaster.
Masonry, Brick, Stucco and Plaster: KILZ ORIGINAL Primer may be used on clean, dry, aged masonry surfaces that have cured (dried) at least 90 days.
Usually, two coats of PVA mixture will give you the best surface for skimming before plastering. Instead of PVA, you could use a bonding agent.
There's no one answer because the number of coats of primer depends on a few factors, such as the color you're painting over, the type of paint you're using, and the condition of the walls or surface you're painting. However, two coats of primer are typically used for most projects.
Cons of the Skim Coats
Skim coating walls seems to be more tedious than expected. It can consume more time for those who aren't familiar with the steps used to repair walls. This process can also be intensive labor-wise and energy-consuming.
The original, most-trusted conventional weight all purpose joint compound for all phases of drywall finishing. USG Sheetrock® Brand All Purpose Joint Compound is a best-in-class solution for embedding tape with superior filling and finishing qualities and is an excellent choice for skim coating.
Don't paint directly over new plaster walls because the glossy surface can prevent the paint from adhering effectively.
If your walls are in a good condition and you're using a similar paint to the existing paint, you may not need primer. Always check the instructions on your chosen paint for guidance on using primer.
Application/Usage:
Brush down highly polished surfaces with a stiff bristle brush before priming. 2. Apply 2 coats of BAL Bond SBR using a clean brush from a container, diluted or undiluted as appropriate (See USAGE above). Allow to dry between coats.
Mist coat paint is simply watered-down emulsion paint, which acts as your primer. All you need to do is get some white emulsion paint and thin it out with water – it's that easy! Ten parts paint to one part water should work. If you don't fancy watering down your paint you can also use Dulux Sealer for Plaster.
For newly skim-coated walls, use a high-quality PVA (polyvinyl acetate) drywall primer. This type of primer is designed to seal the surface, provide a good base for paint, and ensure even coverage. It's specifically made for new drywall and skim coats, so it should work well for your needs.
KILZ PVA DRYWALL PRIMER is designed for use on new drywall. It is a fast-drying, interior water-based primer formulated to prime and seal new, uncoated drywall and reduce the number of topcoats required to achieve a uniform, professional quality finish.
Be prepared to apply at least two coats for a smooth finish. You don't need to wait for the first coat to dry before applying the second. As soon as you've finished covering a wall, go back to the beginning for your next coat, dragging your trowel.
The first alternative is to use joint compound rather than skimming the surface with plaster. The compounds are for filling joints between plasterboard or any gaps and holes. However, you could use it to give an entire wall a smooth coat. You apply it with a trowel or putty knife.
You don't have to sand between coats; just knock off lumps or proud mud lines with a 5- or 6-in. putty knife to avoid streaks in the next coat. Brush off the wall and you're ready for the next coat.
PVA primer: PVA (polyvinyl acrylic) primer is a water-based primer that is specifically designed for use on new drywall. It is easy to apply, dries quickly, and helps to seal the surface, making it less porous and more receptive to paint.
You only need to sand if there are brush strokes or other blemishes. Also you don't need to sand between coats.
Walls with a skim-coat will need a full coat of primer. Patched areas should be spot-primed before painting too, so if you've filled in nail holes or patched dents, be sure to prime those spots after sanding.
Remove wallpaper or panelling
As with most DIY projects, the surface you apply the skim coat to needs to be clean dry and sound and this means all wallpaper, flaky paint and loose plaster needs to go as it will either stop the plaster from sticking or at least cause you a patchy final result.
If you have various stains, shellac Bonding primer is the ideal choice. It can be used to cover rough surfaces and old varnish as well as metal and ceramic.
Start by cleaning your surface before removing any loose paint and rust with spirits and sanding. Repair any holes or imperfections with a metal putty, wipe the surface clean and begin priming. Apply evenly on a dry and non-windy day if working outdoors.