Before applying a coat of wet paint to a wall or repainting a piece of furniture, you need to prepare the surface you're working on.
This helps ensure that the finished product looks good and lasts for years. The first step is to tape off any areas you don't want the paint to touch, such as mouldings. Use painter's tape for this task; it has an adhesive that won't damage surfaces when removed. If your room doesn't have trim, line the perimeter of your room with masking paper before painting that area. Next, prime walls or ceilings in preparation for painting them white. It makes any colour you apply after that look brighter and richer by comparison. To prime, use an oil-based primer, which most paint manufacturers sell. Oil-based primers have a longer drying time, so they help give you more time to smooth out any imperfections in the wall before painting it white. However, don't use oil-based primer on wood because it can raise the grain of the wood and cause problems when applying a coat of paint. Note, if you are using water-based paint, apply a water-based primer. Similarly, apply oil-based primer to a surface prior to applying oil-based paint. Always leave the primer to completely dry before starting to paint walls.
If you're painting over wallpaper, spend whatever time is necessary to remove all of it first; otherwise, your new coat will peel off with the old paper wrecking the entire painting job. To remove wallpaper, soak a sponge or brush in warm water and add some mild dishwashing liquid (or another mild detergent). Cover this sponge with plastic wrap and cover the area where you're working with a drop cloth, using weights to hold it down. Then moisten the wall and wait a few minutes for it to soften up. Chisel away any parts of the wallpaper that won't come off with the moistening. If you still can't remove all of the paper, use a spray bottle filled with water and spray the surface until it softens enough so you can scrape it off.
Using this technique to remove wallpaper won't cause damage to paint or plaster behind the paper, two substances that would be adversely affected by water if applied directly. However, your walls may need repairs before they're ready for painting; fill holes and cracks using spackle paste. To prepare plaster for painting, apply an anti-fungal agent. This will prevent it from turning yellow. On walls that may get damp, seal the surface with masonry paint formulated for masonry surfaces; on all other walls, use an oil-based primer before painting them white. Preparation is key to long lasting paint.You'll also want to clean dirty walls before painting. Wash dirt and grease off kitchen walls with a cloth dampened in warm soapy water, then rinse the surface with clear water to remove any soap residue. If your walls have been painted before but are looking worn, you may want to lightly sand them with fine-grit sandpaper just before applying primer. This will help it stick better. However, if you're going to use an oil-based primer, sanding isn't necessary.
After this preparation, your walls should be ready to receive a new coat of paint. The rule of thumb is to apply the next coat of paint only after the current coat of paint dries.It is critical to prep walls thoroughly before painting. You will need to move furniture or remove pictures or fittings on interior walls before anything else. For wall fittings and light switches that cannot be removed, tightly wrap them with a plastic bag and fasten them with masking tape. It is easier to unscrew outlet covers and switch plates to apply paint freely. Always wear safety equipment. For areas high up the wall, have a step ladder ready. Have the right tools such as masking tape, putty knife, stir stick, paint roller brush or related brushes, and sanding block or sandpaper. Scrap off loose paint with a putty knife. Smoothen the surface by sanding down uneven surfaces. Start with medium-grit sandpaper. Finish with finer grade type to ensure you attain a smooth surface. Apply gap filler to fill cracks and nail holes. A joint compound should be used to fill larger holes. Use a damp cloth to wipe any excess filler from the surface. Apply painter's tape to wood trim areas and tape off one paint colour section from the other. For unlevelled surfaces, apply spackle compound, then sand it down to level up such areas. Before you start painting, spread drop cloths on the floor. Paint splatters and drops will fall on the drop cloths instead of the bare floor. You do not need to cover the entire room floor. Just cover along the length of the wall where the paint drops will fall. Once you have finished painting, clean the brushes with water and soap to preserve them for the next paint job.
Painting over old or cracked paint can cause problems since the new coat doesn't bond to whatever is underneath. While this won't affect your walls much in the short term, it could cause peeling or flaking when you apply a second coat of paint or when you try to change colours later. If you're painting over the same colour, you might get away with applying a coat of primer first. However, if you're changing colours or just applying fresh paint, consider stripping existing paint off instead. To get a clean surface, apply a liquid chemical stripper to the surface using a sponge brush. Let stand for about 15 minutes before rinsing it off completely with water. If the paint comes off easily, then go ahead and apply your primer or new paint. If not, repeat until it does.
Before painting your walls white, then follow these guidelines: If they aren't dirty and haven't been painted before, paint them with an oil-based primer; if they've been painted before and are in good condition (no holes or cracks), paint them with an oil-based primer; if they've been painted before and need repairs (holes or crevices), strip existing paint off before applying primer; clean any dirt or grease off with a damp sponge or cloth dampened in lukewarm water, rinse with clear water and let dry completely; finally, apply your primer.
Primer is made of a thin mix of two parts paint and one part thinner. It's important that you buy the right type; most wall primers are latex paint with water as their thinner, but some may be acrylic (a mix of polymer and water) or oil (just like regular paint but uses mineral spirits in place of water). Oil-based primer needs to have a bit more volatile substance, mineral spirits, than regular paint so it can dry entirely through evaporation over time. That's why it isn't recommended for areas where moisture tends to gather. If this will be a problem, get an oil-free primer instead. There are other types of primer available for specific purposes. One is "kraft" primer, an oil-based product that has the consistency of peanut butter and is used as a sealer before painting plaster or masonry walls. Another type, known as "impregnator" primer, is also recommended for unprimed plaster and masonry surfaces; it's designed to penetrate these porous materials and prevent bleed-through of dye and pigment from paint coats applied above it.