Give the final coat a full day to dry, then you'll sand the drywall for that ultra smooth finish. In color, it may not look perfectly even, but as long as it's super smooth, the primer will do the trick to even the color prior to paint.
The answer to ur question is the quality of finish on the skimming. When painting onto new plaster, it's generally recommended to sand the walls lightly before painting. Sanding helps smooth out any imperfections in the plaster and provides a better surface for the paint to adhere to.
You should do a little bit of sanding between adding coats of mud. Knock down any ridges or significantly imperfect areas through sanding, which should help you apply the next coat of mud smoothly. If your first coat of mud is pretty smooth after it dries, a quick sanding is all you'll need.
Let it dry, sand it, and do another thin skim coat. Let that dry. Sand it and prime. Let the primer dry and touch up the bad spots. Let that dry and sand it. Prime the spots. Wait for that to dry and sand your primed wall.
Give the final coat a full day to dry, then you'll sand the drywall for that ultra smooth finish. In color, it may not look perfectly even, but as long as it's super smooth, the primer will do the trick to even the color prior to paint.
Drywall mud can take as long as 24 hours to dry for thick applications. The 24-hour drying time recommendation can be applied to nearly all factors. Some manufacturers will bring down that number to 12 hours if a few shortcuts are applied to help speed up drying time without affecting the finished product.
Any pro will tell you that you must thin it down. You want it smooth and spreadable like pudding. You might have to remove a scoop of mud to make room for some water.
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.
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.
You should prepare to apply at least two coats, in order to achieve a smooth finish. However, if you can still see obvious grooves and indents after the second coat dries, you can trowel on a third coat using the method mentioned in Step 7 of this guide.
Before painting on newly skimmed walls, you'll need to wait until the plaster is completely dry. In good conditions – typically in summer months – this will usually take around three days. However, we'd recommend leaving it for at least two weeks if possible to be safe.
Skipping the prep before painting your walls can mean you're left with an uneven finish, unsightly paint bubbles and obvious imperfections, such as holes and cracks. Taking the time to prep before you roll paint onto a wall helps you achieve a flawless finish that stays that way for years to come.
Don't paint directly over new plaster walls because the glossy surface can prevent the paint from adhering effectively. Instead, once you've protected your work area with dust sheets, lightly score the walls with 150-grade sandpaper to create a key and improve adhesion.
Allow the first coat to dry completely, which can take anywhere from a few hours to overnight, depending on humidity and temperature. Once dry, lightly sand the surface with fine-grit sandpaper to remove any ridges or bumps.
An orbital sander is an option for a large drywall project. This tool is lightweight and can perform the task in less time, but as a power tool it must be used carefully to avoid damaging the drywall surface. Use fine grit sandpaper, between 150 and 180 grit, to achieve the desired results.
Good air flow also helps speed things up. To dry mud quicker, pros use fans for better air circulation. Some also use heaters to warm up the room.
Another common blunder is using too little or too much joint compound. Uneven application can cause visible seams, cracks, or bulging joints, compromising the overall appearance of your walls.
Premixed joint compounds come in a variety of consistencies, depending on the brand, the factory where they were produced, and even regional formulas. The joint compound manufacturers allow users to add water to the compounds, but the formulas are designed be thinned with water only.
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.
Temperature and Humidity Changes: Fluctuations in temperature and humidity can cause materials to expand and contract. This movement can lead to cracks in plaster over time, especially if the plaster and the substrate have different rates of expansion and contraction.
During the skim coat drying process, minimize airflow in the room. Keep doors and windows closed, as air draft may disrupt the skim coat and cause air bubbles formation. Maintain the environment with stable humidity and temperature levels.