This Old House™ Paint FAQ's
- Before starting an exterior painting project, what preparations must be done for optimal results?
- When is using a primer necessary?
- What type of primer should I use?
- Is it okay to mix different brands of primers and topcoats?
- Which type of paint should I use, oil or latex-based?
- When living in high-humidity regions, what protective benefits should be taken into consideration when selecting paint?
- What type of brush should I use for my painting project?
- What is paint anyway?
- Do pigments determine the quality of paint?
- Should latex paint be thinned?
- Are there different types of alkyd resin?
- Are paints containing alkyd resin of top quality?
- Will oil-based or alkyd enamels yellow?
- Where are flat finishes used?
- Why would a flat finish be preferred over a higher sheen finish?
- What types of flat wall finishes does ICI Paints manufacture?
- What is an acrylic paint and how does is differ from an alkyd?
- What is the typical drying time of a latex flat paint?
- What factors increase the drying time of paint?
- How large an area can be painted with one gallon of latex flat paint?
- How is the sheen of paint measured?
- How is the gloss of enamel paint measured?
- Why are eggshell, low lustre, semi-gloss and gloss enamels more durable than flat finishes?
- What advantage does a gloss enamel have over a semi-gloss enamel?
- How should latex semi-gloss be thinned?
- Will gloss enamels cover in one coat?
- How do I estimate my paint needs for interior rooms?
- How should brushes and rollers be cleaned?
- What is the function of a primer-sealer on new plaster surfaces?
- Besides primer, what other products may be used as the first coat on drywall?
- Is an entire prime coat needed if the surface has patched areas?
- Why is it poor practice to put low cost flat paints on high usage wall surfaces?
- Why do surfaces previously painted with low cost flat paints require primer before being repainted?
- What is a "self-sealing" flat paint or enamel?
Q: Before starting an exterior painting project, what preparations must be done for optimal results?
A:
Start with a clean, sound surface:
Clean
Scrub off as much dirt and chalk as possible. If mildew is on the surface, remove it with a combination of dishwashing detergent (quarter cup), household bleach (quarter cup), and water (three cups). Make sure to wear safety goggles and gloves during this process. Rinse the detergent formula off completely to ensure that the primer and/or topcoat* will adhere to the surface properly. When it is possible that lead paint may be present, make sure to use proper surface preparation techniques outlined on the can label or in readily available lead paint safety brochures at your local paint store or home improvement center.
Sound
Scrape off flaking or peeling paint, as well as flaking wood. If the paint is peeling, putting a topcoat over it will not make it stop peeling. The new coat of paint will actually peel off with the older paint.
Q: When is using a primer necessary?
A:
A primer is a key tool for achieving optimal results from the topcoat. Many primers provide protection or resistance from various elements, such as staining (such as from tannin on redwood/cedar) and mildew. In terms of choosing a topcoat color, certain shades suggest the usage of a primer to provide better hide. Follow paint directions and assess the elements and surface you will be painting to determine if a primer should be used.
Q: What type of primer should I use?
A:
A latex primer offers the most versatility and works well on most any surfaces. Latex is designed to be flexible after it cures. This flexibility is a good choice for wood or plywood that may tend to crack. It is also blocks calcium build-up on cement and stucco surfaces (which prevents a white powder formation on the surface of the topcoat after curing).
An oil-alkyd formula is the best choice for blocking tannin stains (yellowish-brown stains caused by redwood or cedar wood). However, oil becomes brittle over the years after curing and can attribute to surface cracking and flaking. Additionally it can feed mildew. Choose oil-alkyd formulas primarily for wood applications that would benefit more from the oil.
Q: Is it okay to mix different brands of primers and topcoats?
A:
It is a bad idea to mix different primer and topcoat brands. A manufacturer will not test their brand of primers with different brands of topcoats. Manufacturers test their own primers and topcoats to make sure they are optimized to work together for the best results.
Q: Which type of paint should I use, oil or latex-based?
A:
Latex paint is the most versatile coating. Latex is water-based, so it is low-solvent and can be cleaned up easily with soap and water. It also retains its flexibility over time which makes it appropriate to use on most surfaces, provides good color-retention and excellent mildew and algae resistance. This Old House™ paint is a 100% acrylic latex paint that will provide optimal coverage on old or new wood.
Oil-based paint is best for old wood that is porous, dry or chalky. The oil tends to soak in and penetrate the wood better than latex. The downside of using oil paint is that the color can fade and loose its sheen faster than latex, is more susceptible to mildew damage and becomes less flexible over time creating cracks.
Q: When living in high-humidity regions, what protective benefits should be taken into consideration when selecting paint?
A:
Mildew and algae resistance is especially important for homeowners in high-humidity climates. Algae can grow on an inert surface because it only needs water and sunlight to grow, while mildew needs organic food such as sugar from wood or oil from paint to develop. Most paint brands focus only on mildew, not algae protection. This Old House paint in the flat and satin sheens protect against both.
Q: What type of brush should I use for my painting project?
A:
A polyester brush is best for latex-based paints. Natural bristle brushes become very wilted in latex-based paint, but they work well with oil-based paints.
Q: What is paint anyway?
A: The chemical combination called paint is an intimate mixture of three principal components: Pigments, Resin (binder), and Solvent.
Q: Do pigments determine the quality of paint?
A: The level of any one pigment (such as titanium dioxide) is not, by itself, a good indication of quality. The properties and performance of the paint are a result of the particular combination of pigments and vehicle in the dry film. Example: durability (hardness) can be obtained with a combination of soft pigments and hard resin or hard pigments and a flexible resin.
Q: Should latex paint be thinned?
A: Normally no thinning is required. In general, thinning any paint reduces the film build, hiding and sag resistance. When applying with a sprayer, thin sparingly with clean water as needed. The maximum amount of water to be used is 1 quart/5 gallons.
Q: Are there different types of alkyd resin?
A: 'Oil length' is a term you may encounter, in phrases such as 'long oil alkyd'. Long oil paints are formulated with a high ratio of oil to resin to deliver maximum flexibility and penetration into the substrate. (e.g., exterior wood primers) Short oil paints are formulated with a low ratio of resin to oil to deliver maximum hardness, durability and fast dry. (e.g., machinery enamels)
Q: Are paints containing alkyd resin of top quality?
A: Paints containing alkyd resin can vary from the highest quality down to the lowest quality. The type and amount of alkyd resin and the pigmentation determines a paint's quality.
Q: Will oil-based or alkyd enamels yellow?
A: All alkyd or oil-based enamels will yellow in the absence of light or exposure of the paint to ammonia fumes during the curing process.
Q: Where are flat finishes used?
A: Flat finishes are ideal for broad wall surfaces and ceilings because of their uniform, non-glaring appearance. Examples include hospitals, schools, institutions, offices, factories, apartments and houses.
Q: Why would a flat finish be preferred over a higher sheen finish?
A: Flat finish surfaces scatter the reflection of light and help minimize surface defects. Glossy finishes reflect light more directly to the eye (more glaring).
Q: What types of flat wall finishes does ICI Paints manufacture?
A: The three principal types are acrylic copolymer latex, vinyl acrylic latex and alkyd resin base.
Q: What is an acrylic paint and how does is differ from an alkyd?
A: An acrylic paint is a superior type of latex paint made with an acrylic resin and is generally water-thinned. An alkyd paint is a solvent-thinned paint made with an alkyd resin. In exterior finishes, the acrylic paints have better flexibility and color retention (or fade resistance.)
Q: What is the typical drying time of a latex flat paint?
A: Under normal conditions, latex flat paint dries to touch in one half-hour. It may be re-coated in two hours.
Q: What factors increase the drying time of paint?
A: Low temperature, high humidity, thick film application and poor ventilation.
Q: How large an area can be painted with one gallon of latex flat paint?
A: Generally, on smooth walls the practical coverage (also called the 'spread rate') is 400 square feet per gallon. This is enough to paint the walls in a 12 X 13 foot room.
Q: How is the sheen of paint measured?
A: The sheen of paint is measured at an angle. The two standard angles are 60° (generally used for paints with some reasonable level of sheen) and 85° (used for paints with very low sheen). Looking straight at the surface (which is considered 0°) makes it difficult to compare one paint sheen from another.
Q: How is the gloss of enamel paint measured?
A: The degree of gloss of enamel is measured by means of a Glossmeter, which measures the light reflected from a painted smooth surface where the angle of incidence from the light to the painted surface is 60 or 85 degrees. The ASTM D-523 standard gloss ranges for consumer paints are:
- Flat: below 15 units @ 85
- Eggshell: 5-25 units @ 60
- Satin (low lustre): 15-35 units @ 60
- Semi-Gloss: 30-65 units @ 60
- Gloss: over 65 units @ 60
Q: Why are eggshell, low lustre, semi-gloss and gloss enamels more durable than flat finishes?
A: Enamels have more resin solids in proportion to the pigment. It is this high resin content which give an enamel its sheen and toughness. As the amount of resin increased, the sheen or gloss of the paint increases.
Q: What advantage does a gloss enamel have over a semi-gloss enamel?
A: No real advantage. The choice between the two is really just a matter of personal preference.
Q: How should latex semi-gloss be thinned?
A: As mentioned in the previous module, thinning is not normally needed. If necessary, thin sparingly with clean water. Maximum thinning is 1 quart of water to 5 gallons of paint.
Q: Will gloss enamels cover in one coat?
A: Gloss enamels are high hiding and will cover most surfaces in one coat as long as the color contrast is not too great.
Q: How do I estimate my paint needs for interior rooms?
A: Measure the length of each wall and add them together; multiply this by the height of the room. Measure the door and window openings and subtract them from the total. If the ceiling is to be painted, multiply the length by the width and add to the total. This will give you the square feet of area to be covered. You will need approximately one gallon of paint for every 400 sq. ft. of surface to cover.
Q: How should brushes and rollers be cleaned?
A: If latex paint has been used, only soap and water are needed to clean equipment. If alkyd paint has been used, paint thinner is needed. Paint thinner is the same as mineral spirits (an aliphatic hydrocarbon).
Q: What is the function of a primer-sealer on new plaster surfaces?
A: The primer-sealer seals the surface uniformly and provides a sound, non-absorptive surface for subsequent coatings.
Q: Besides primer, what other products may be used as the first coat on drywall?
A: Most latex flats are self-priming and the application simply consists of two coats of the finish product.
Q: Is an entire prime coat needed if the surface has patched areas?
A: If the finish is to be flat latex wall paint, either latex primers or the latex wall paint itself may be used for spot-coating. If the finish is to be enamel, prime the entire surface.
Q: Why is it poor practice to put low cost flat paints on high usage wall surfaces?
A: These products may contain a very high amount of coarse-textured pigment for cheaper material cost and for 'dry-hiding'. These cheaper flat paints do not wash well; they burnish and mark easily and usually require a primer before repainting.
Q: Why do surfaces previously painted with low cost flat paints require primer before being repainted?
A: Low cost paints tend to be more porous. Many coats of flat paint will create a suction effect. Therefore, if a porous surface is not primed before repainting, the finish coat may not be uniform is sheen or color.
Q: What is a "self-sealing" flat paint or enamel?
A: Generally, these are higher quality paints with a film density that prevents excessive penetration; this permits use over most surfaces without primer. These paints serve as their own primer when a second coat is required.
