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When using an oil-based product, how much time is needed for the product to set up sufficiently to withstand rain or precipitation?

A minimum of eight hours is recommended when the temperature is above 70° F. The cooler the temperature the longer the wait.

What is sweat-in or induction time?

These terms refer to the waiting period required between the time you mix and the time you can start applying a two-part product, such as an epoxy. This allows the necessary chemical reactions between the two parts to begin so the coating will cure and perform properly.

Mixing instructions for two-part epoxies and urethanes mention a potlife of so many hours. Does this mean the paint turns solid in that amount of time?

In some high-solids materials, the liquid will become solid at the end of the potlife. In most cases, though, the potlife refers to the amount of time you have to apply the coating before it gets to a critical point in the chemical reaction between the two parts. After the potlife period expires, the material will become difficult to apply and the adhesion, cure, and performance of the coating will be adversely affected. When working with these types of products, it’s best to mix only what you can use within the potlife listed by the manufacturer.

Does bleach really kill mildew on a wood?

Chlorine bleach (sodium hypochlorite), when mixed in proper proportions, removes mildew stains and kills the living mildew spore growth on the wood surface. However, it will not kill mildew deep in the wood.

Is it always bad to paint in direct sunlight?


What kind of paint works best on galvanized surfaces?

After allowing the galvanized surface to weather for six months or chemically cleaning it to remove any oil or remnants of the galvanizing process, you can apply two coats of an acrylic latex paint directly to the metal or a special galvanized metal primer topcoated with an alkyd or latex product. Do not apply an alkyd directly to a galvanized metal surface because the oils will react with the zinc used in the galvanizing process, causing the alkyd to peel.

What is the best paint to use on handrails, material handling equipment and other surfaces exposed to heavy wear-and-tear?

A two-component polyurethane coating will produce a hard, durable finish as well as provide effective colour and gloss retention in areas that must withstand a lot of physical abuse. Over properly prepared and primed substrates, two-component polyurethanes provide a tough, long-lasting finish.

What makes a better paint? Do more expensive paints contain more durable pigments and resins?

Yes they do. You hit on some key items that improve the quality of finish. The resins along with the binders give you the quality of finish. Also, the way the product is produced can impact the quality. Paint goes through a piece of machinery called a ball mill. This grinds everything together. The size of the balls used and length of time it goes through the mill impacts the fineness of the pigment grind, which impacts the quality of the product.

What basic ingredient gives paint its hiding power?

Of the three main paint ingredients – pigments, solvents and binders – the pigment provides hiding power and gives paint its colour and shading. The solvents carry the paint to the surface, then evaporate, leaving behind a film of paint; the binders are bonding agents that hold the paint together.

I see the term “Volume Solids” in most specifications. What does it mean, and why is it so important?

Paint is made up of four basic elements: solvent, binder, pigment and additives. The material left on a substrate after the solvent evaporates and the coating cures is its solids content. When calculated as a percentage of the total gallon of paint, the solids are referred to as “Volume Solids.” A higher percentage of Volume Solids is usually an indication of a better quality paint, because more binder and pigment are left to protect the surface compared to a coating with a lower Volume Solids rating.

The VOC requirements I read about are expressed grams per liter, but I buy paint in gallons. How do I know if I’m in compliance?

Simply divide the grams per liter amount by 120 to determine the pounds per gallon figure. For instance, a product that has a VOC of 250 grams per liter would have 2.08 pounds per gallon, because 250/120 = 2.08. To convert from pounds per gallon to grams per liter, multiply the number of pounds by 120.

What chemical component of paint is responsible for the sheen level?

The resin is responsible for the sheen level (latex & alkyd).

What factors are most significant in determining paint quality? We are about to paint a Victorian home and are looking for the highest quality exterior paint. Longevity without shrinking, cracking or loss of luster are our primary concerns.

The main factors are the type and amount of resin (the binder that holds the paint together), type and amount of pigment, volume solids and film thickness. A high quality paint like Sherwin-Williams Duration, has enough volume solids for applying one coat at 2.8 mils dry film thickness. This is the longest lasting coating that Sherwin-Williams has to paint the exterior of a home.

It seems that darker coloured acrylic latex paint has a longer service life than lighter colours. Can this be true?

Yes, it’s possible. Even if all other factors are equal, this situation can occur if the darker colour is based solely on a durable oxide “earth” colour, such as red iron oxide, and the lighter colour contains a portion of titanium dioxide (a white pigment), which contributes to chalking.

Will acrylic latex house paint stand up to a harsh seashore environment where there is high humidity, wind-driven rain and salt? Or must an oil-based paint be used?

Acrylic latex paints have demonstrated outstanding durability in the most rugged environments including direct sunshine, moisture from rain and snow, and at the seashore. Due to the superior adhesion of acrylic latex paints, they don’t tend to blister, crack or flake when exposed to rain or high humidity. Remember that the most important part of repainting is surface preparation. While priming is usually not necessary for some repaint surfaces when using an acrylic latex paint, it’s a good idea to prime any bare wood. For the best performance in the seashore environment you describe, it’s advisable to carefully wash away any salt deposits found on the surface to be painted along with any “chalk”.

What types of cleaners can I use to remove mildew?

Try using a solution of one quart household beach in three quarts of water. Apply the solution to the area with mildew and then rinse off with water. Never add detergents or ammonia to the bleach/water solution. Always protect your skin and eyes against splashes.

How do I remove insects from fresh paint?

If bugs land on the wet paint, let them stay until the paint dries. Once dry, remove them with a clean paint brush. You might end up with small, unnoticeable “bug prints,” but that’s better than removing the bugs and trying to touch up partially dry paint. Using a faster-drying exterior-latex paint, like Sherwin-Williams SuperPaint, is helpful in this situation. Latex paint dries quicker than oil-based paints, giving insects less time to get stuck in the coating.

What is the best way to clean a new galvanized surface before painting?

If it is not practical to allow the surface to weather for six months before painting, it must be cleaned with a solvent to remove any surface contaminants and oils applied by the manufacturer to prevent oxidation of the zinc in the galvanized coating. This is best accomplished by using a water-soluble degreasing cleaner applied with a clean cloth or sponge. Change sponge or cloth and cleaning solution frequently so the dirt and oil are removed from the surface, not just spread to other areas. Rinse the surface thoroughly and allow to dry before painting.

What determines if a joint should be recaulked? Should old caulk always be removed?

If the old caulk is cracking or pulling away from the surface, dig it out and replace it. Prime the bare wood then re-caulk. Any butt joint in siding or other joints between two pieces of wood should be caulked. You DO NOT want to caulk the lap joints of siding since they allow moisture to get out from behind the wood.

How do I determine when a concrete floor is ready to paint?

New concrete should cure for at least 30 days. Check for moisture by taping a 2’x2′ piece of 4-mil plastic to the floor with duct tape. If no darkening of the concrete or condensation is evident after 24 hours, the floor is dry enough to paint. The floor should be thoroughly cleaned and acid etched prior to application.

Can I apply latex paint over a surface finished with an oil-based product?

Yes you can. You have two choices to do this. First would be to wash the surface, sand and then clean the sanding dust off. You may then apply your latex paint over the oil base paint. That process works for both interior and exterior applications. Your other option is to wash the surface and then apply a coat of a bonding primer and then topcoat.

Can acrylic latex house paint be applied over gloss alkyd paint? Is special prep work necessary to ensure good adhesion?

Yes, to both questions. but, to ensure good adhesion, glossy surfaces must first be washed clean and then sanded to allow the paint to “grip” the surface. Gloss alkyd paints that are exposed to harsh weather conditions have a tendency to “chalk” – that is , the old paint film develops a faded, powdery substance on the surface. So it’s best to wash off any excessive chalk prior to applying an acrylic topcoat. When painting bare surfaces, use an appropriate primer before applying the topcoat. This will ensure the best adhesion and long-term durability.

Is it advisable to apply an alkyd over an existing latex?

No, it isn’t. The alkyd layer will get hard and brittle as it ages, but the latex underneath will remain flexible. As time passes, the latex layer will flex and move with the expansion and contraction of the substrate more than the alkyd topcoat will. This will compromise the adhesion of the alkyd to the underlying latex and cause the alkyd topcoat to peel.

How do I find out if the paint on a house exterior is latex or oil? Is there a quick test?

If the old paint is peeling, take a good size piece of the peeling paint and hold the edges of it between your thumb and index finger. Exert pressure on both sides of the chip. If it is very flexible and bends easily, it is probably latex. If it is hard, brittle and breaks instead of bending, it is most likely oil-based paint. Another way to test the paint is to wet a rag with denatured alcohol and rub the surface of the paint. If the paint softens or rubs off, it is most likely latex. An alcohol test usually will not affect an oil-base paint.

Why do I need to use a primer instead of just using two coats of the finish paint?

A primer is beneficial because it helps provide a uniform surface that promotes good adhesion of the topcoat. A primer can also serve a special purpose by sealing a porous surface, blocking out stains, preventing rust formation on iron and steel, and preventing tannin bleed on wood. Most finish paints are designed to provide a decorative or protective finish for a substrate. In most situations, they do not provide the features of a primer, so it is always important to follow the manufacturer’s recommended coating system.

What is the best method of touch-up?

To achieve acceptable touch-up results, it’s important to apply touch-up by the same method as the original application, if possible, to avoid having any difference in sheen or texture. Be sure to use paint from the original batch, reduced 25 to 50 percent, and only apply a thin coat. It’s also best to apply the touch-up paint under similar temperature and humidity conditions as the original.

How can I avoid overlap marks when I’m painting?

Try not to paint too large of an area at one time. Overlapping occurs when a freshly painted section begins to dry before you start painting the adjoining area.

What does saponification mean?

Saponification is the reaction of an alkaline surface, such as concrete or galvanizing, with the oils in a coating. This reaction forms a soaplike material at the coating/substrate interface and eventually causes the coating to peel.

The following day after painting the siding on a house, I noticed wrinkles in various areas of the finish. What went wrong?

When paint is applied in excess of the recommended wet film thickness or when two coats of paint are applied too quick. This will not allow sufficient drying and wrinkling may occur. This surface imperfection should be corrected once the paint film has dried by power sanding. The smooth area should then be primed with a quality oil or latex primer prior to topcoating.

I recently painted a house with vertical wood siding white, but now notice rust staining from nails. What should I do?

If steel nails or uncoated steel hardware is exposed to air or moisture, unsightly stains can develop on adjacent paint surfaces. This problem is easily rectified by sanding the metal clean and applying a rust-preventative primer. Nails should then be countersunk and caulked or wood filled.

What usually causes a coating to fail?

The most frequent causes for premature paint failure are as follows:- insufficient surface preparation; low film build; improper coating was used; product not applied as directed; or environmental conditions (moisture, fumes, chemicals, etc.).

What causes white powdery deposits on masonry surfaces, and how can I fix them?

The deposits, known as efflorescence, are caused by moisture in the masonry. The moisture dissolves salts in the masonry — the mortar, block, concrete, etc. — and is drawn to the surface by the heat of the sun. The water evaporates, leaving behind white deposits that must be removed before painting. After you find and fix the source of the moisture, remove the efflorescence with a wire brush and coat the surface with a masonry primer and topcoat.

What causes small cracks to form on a recently painted wall?

This problem is commonly called “alligatoring.” The most common cause of alligatoring is the application of too thick of a paint film. The surface of the film dries first, with the rest of the film taking longer to dry than normal. When the underside of the paint finally does dry, it shrinks, causing the top of the film to pull apart and leaving unsightly cracks. You can prevent this by applying the paint at the manufacturer’s recommended thickness and spreading rate. A less frequent cause of alligatoring results from painting over a contaminant on the surface such as oil, silicone, body oils, hair spray, etc. You can prevent this by thoroughly cleaning the surface before painting.

I have tried everything I can think of to keep paint on exterior window sills. What do you suggest?

You should prepare and repaint the entire window unit. Begin by removing all loose paint with a wire brush or scraper. Don’t forget the ends and underside of the sill, as peeling or cracking often begins there. Next, remove any old caulking from the joints in the frame and the areas where the frame meets the sill and where the frame and sill meet the siding. Finish the surface prep by sanding the wood until it has a bright, new look. This removes any decayed wood fibers from the surface and provides a sound surface to paint. Now apply one coat of Undercoater 450, again paying special attention to the end grain and underside of the sill.

After the primer dries, apply an acrylic latex caulk to the joints in the frame, the space between the frame and sill, and the space between the window and the siding. Follow with two coats of a top-quality acrylic latex satin or gloss house paint, like Kem Gloss. After you replace the storm window, make sure the drain holes at the bottom are open. This will prevent the condensation that builds up on the inside of the window from collecting on the sill.

What’s the drying difference between alkyd and latex?

Latex paint dries to the touch in one hour and cleans up with water. Alkyd paint dries to touch overnight and cleans up with solvent.

How can walls be “untexturized” and at what cost?

There are a couple of different options. One would be to have more material added on top of the texture and then troweled to a smoother finish. This could add a lot of weight and “could” cause some adhesion problems. The other choice is to have the texture sanded smooth. That’s a lot of dusty work. Whichever method you choose, make sure the walls are properly primed before applying a topcoat so you get a uniform appearance.

When texturing a ceiling, how much joint compound, water, and paint do you use proportionately?

The ratio is one gallon of paint to a pail of joint compound. This ratio may vary depending on the manufacturer of the joint compound.

Why would a popcorn texture peel and fall off in sheets after a latex paint is applied?

When latex is applied over a “popcorn” ceiling, the water in the paint can break down the adhesive bond between the texture and the substrate, allowing the weight of the texture to pull the material off the ceiling. Applying an alkyd primer before repainting with latex will usually alleviate the problem.

What happens to an acrylic latex paint if it is diluted with water? In what way would this lessen the durability of the dry paint film?

When water is added to paint, the solid content of the system is diluted. As a result, the diluted paint will not form as thick a dry film as the paint manufacturer intended. Since film thickness is important to durability, these paints will perform poorer than expected. Hiding can suffer, too.

I occasionally have problems with exterior doors being difficult to open after they’ve been painted. What causes this and how do I prevent it?

Latex paints contain chemicals called plasticizers that allow proper film formation and keep the coating flexible. Many vinyl and plastic weather-stripping materials also contain plasticizers to give them flexibility. When two surfaces containing plasticizers come in contact with each other, they can have the tendency to stick. This condition, known as blocking, will generally occur during the early curing time of the coating, but it can continue for some time. Blocking can also occur on double-hung windows and garage doors. The easiest way to prevent blocking is to use a non-blocking acrylic, or alkyd base paint in areas where it may occur.