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.
You can use multiple coats of the same join t compound. You need to either sand the previous surface to get it smooth, or if there are ridges you might have luck scraping it with the mud knife. There is a skill and art to finishing walls, takes lots of practice. Starting in a small room is a good choice.
Observe how the plaster behaves – if it sucks the primer in evenly then you can be sure this is will also happen when paint is applied, you may find you need 2 or 3 coats for full obliteration with white paint over the pink finish. For the best results leave 4-6 hours between coats for drying.
Apply each layer of plaster 15-30 minutes after the previous layer. If there is not enough time to finish the project in one day, it is important to apply a thin layer of water over the plaster before applying the next layer. If a new layer is applied to plaster that is already fully dry, it will not bond.
If you still see indentations or imperfections after the second coat dries, trowel on a third coat. After the last coat dries, pole-sand the wall with 120-grit paper.
Generally, it takes a few hours to overnight for a skim coat layer to dry. Always follow the manufacturer's recommendations and allow each layer to dry completely before sanding and applying the next coat.
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. This is where you can focus on smoothing over trowel marks, making for a completely even surface.
Slightly wetting the wall can help the plaster adhere better, but avoid over-saturating it, as this can weaken the plaster's bond. Damp proofing walls before plastering is a vital step in ensuring a durable and moisture-free finish.
Without the mist coat, the plaster will soak the moisture out of the paint like a sponge, causing it to crack as it dries.
For gypsum plaster, we generally recommend waiting around 24 hours between coats. This period allows the plaster to harden and set properly, providing a sturdy base for the next layer. Gypsum plaster is well-suited for interior walls and ceilings due to its smooth finish and quick drying time.
The main telltale sign is a colour change. Wet plaster is darker with shades of brown or red, whereas dry plaster is pale, creamy pink. You are looking for an even colour. Dark patches indicate moisture.
Applying the second coat too early will result in lost time, money, and effort. Not only that but it'll also create additional stress that's not necessary. Applying the second coat too early will result in streaks, peeling paint, and uneven color.
Once the skim coat is applied, it should be left to dry thoroughly. After drying, you can sand the surface to remove minor imperfections and create an even smoother finish.
b) Disadvantages of Skim Coat:
A skim coating is a more workable and skilled process. That's why this process is more expensive than applying for textured walls and ceilings. It needs more time for painting because the skim coat drying process is slow.
Not allowing adequate drying time
Plaster needs enough time to dry between coats. If a first coat is too wet, adding a second coat can cause issues like blistering or cracking. Plaster that is too thick can take even longer to dry. Thicker layers hold more moisture, which can affect the bond between coats.
First and foremost, let the plaster dry. Paint won't adhere properly to wet plaster, so make sure it's fully dried. This takes around 3-5 days for overskim or 4-6 weeks for a new plaster wall, though it can take longer depending on humidity and ventilation.
Although the minimum thickness over any portion of the surface should not be less than 15 mm, the average thickness of the plaster should not be less than 20 mm.
It's as smooth as you can get, or the highest finish possible. There are no bumps, no texture, and it's achieved by multiple skim coat layers that are finished with a good sanding.
Scrape down raised edges, mud those perimeter areas with a 6” knife, sand into existing until you can't see any lines once it's dry. Then you can try blending in the texture with a spray can, or buy a small touch up texture hopper and mix up your own mud(what I would do).
The air bubbles are caused by the joint compound off gassing because either the area was previously painted or a on the second or third coats of mud. This happens because the surface is sealed and the off gassing has nowhere to go but out because it can't soak into the porous drywall surface.
Well it makes it a lot easier to spot when you are sanding touchups • I like to use a little paint pigment. But you could also use chalk • Spinning it up with the Makita 40v and a little mixer I got from the paint store Makita Canada Makita Tools USA.