Primer paints may be oil- or water-based and are used to seal unpainted surfaces to prevent covering coats of paint soaking in. The appropriate type of primer should be used for the surface being painted - wood, metal, plaster or tiles. There are some 'all purpose primers' available which are designed for two or more of these surfaces. You scuff up existing paint for two reasons. First, you want to get rid of any oil, grease or dirt trapped in the top layer of paint. This is the stuff that cleaners and degreasers can't get off. The second reason to scuff is to set up a physical bond for the new primer and paint to adhere to. You want to give the old paint some tooth so the new sticks better. Water-thinned interior paints are calcimine, casein, resin-emulsion, and gloss water paints. Calcimine consists of powdered whiting and clay mixed with an animal-glue binder and a preservative. It cannot be recoated, but can be easily washed off before redecorating.
There is still no standard labelling scheme for paint. The blue globe label, pioneered by B&Q, led to VOC reduction on the mass market and has been adopted by other brands, while the European Ecolabel, recognised in 15 EU member states, looks like a flower and appears on brands such as Earthborn. Germany also has a Blue Angel label and there is a green Nordic Swan as well. You will find more detailed information on most of the paint company's websites, as well as a wealth of practical and design advice. The second part of preparation is surface prep, it addresses covering the surfaces you do not want to get any paint on. A little plastic sheeting will go along way to keeping paint off of floors, window coverings, handrails, cabinets, counter tops, etc... And, if you are not confident with your ability to paint a straight line next to door casing, baseboards, cabinets or hardware protect these surfaces using masking tape. There are two basic types of masking tape white/yellow and blue. The white tape sticks to surfaces better but, can pull off finishes on cabinets or stained woodwork. Blue tape usually will not pull off finishes but, does not stick as well, this will probably be the tape to use for most applications. Always wipe down or dust the surface you will be masking to assure the best tape adhesion possible. If you use blue tape you may need to re-rub down the tape before painting next to it, only mask off areas with blue tape that you will be painting for a given day. With either tapes, do not assume the are a force field that paint will not penetrate, use them as a reference and dry brush the paint next to the edge of the tape and avoid soaking the edge of the tape with a lot of paint, this will cause the paint to "bleed" through giving you an undesired look. If you will need to apply multiple coats of paint, on the first coat, paint as close to the tape as you can, not really getting paint on the tape. With the second coat or a one coat application, you can use the tape more of like a paint barrier and get a little more paint on the tape if you immediately remove each section of tape after painting the section, this will keep the paint from sitting on the tape and "bleeding" behind it. Also, if you get a lot of paint on the tape it is not good to let the paint dry on the tape because some paints (especially the glossier paints) will peel if allowed to dried, with the tape when it is pulled off. White tape should not be left on for longer than a couple of days and I suggest not leaving it on more than a day in areas that receive long periods of direct sunlight. Blue tape can be left on for days, if it will stay on, there again it does not stick as well and may need rubbed down again immediately before painting up next to it. Proper rolling technique: When rolling paint on the wall, get the roller skin evenly loaded with paint and make a V,N or M pattern on the wall, this is to spread the paint across the entire section you will be rolling, then roll back across the section and even out the paint. To properly "lay off" each section, make a final pass of the section applying light pressure to the roller frame arm end of the roller skin and bringing the nap mark (mark created on the pressure applied side of roller skin) across from the beginning of the section to the end of the section, and just repeat all the way down the wall.The V,N or M pattern, will be determine by how far the paint will spread, a V is for less spreading paint and M is for farther spreading paints. Do not "dry roll", which means trying to roll to much of a section at once with very little paint on the roller. Just as important, do not apply to much, if you find you are applying to much, increase the size of the section you are painting i.e. from a V pattern to an N or a N pattern to a M. Five categories are used to describe VOC content. For guidance, a minimal VOC content is up to 0.29 per cent, whereas a very high VOC content is above 50 per cent. All brands have, where necessary, reformulated their ranges to give minimal VOC content.