DIY Guide to House Paints, Primers and Solvents
The best way to make a paint job last is to prepare the surface well and use the right coating. The choices available for finishing and protecting household surfaces are not extensive and only a few basic rules apply so choosing the best coatings to use is fairly simple. Below are some guidelines for choosing paint, both for protection and appearance, as well as some tips for choosing a color and finish that can make the job go a bit easier. Also find alphabetical listing of paints, primers, thinners and solvents to guide your choices.
Paint can be placed into two general categories: water-based coatings like latex, and oil-based coatings like alkyd. No matter which type, virtually all paint coatings are made with the same basic ingredients: solvent, binders, pigment and additives.
The solvent acts as a delivery system for the paint, evaporating as the coating dries, leaving the binders and pigment behind on the wall. The binders are what give paint its body, as a general rule the more binders the better the paint quality. Pigment is what gives the coating its color, the more pigment the better the coverage. Additives can be any of a number of ingredients added to make the coating perform a particular function such as retard mildew.
For water-based coatings the solvent is water and the binders are usually acrylic or vinyl, or a combination of the two. These coatings are very flexible and tend to "breathe", allowing water vapor to pass easily through walls. They dry very quickly and can usually be recoated the same day. They are also easy to work with and clean up with soap and water.
Oil-base solvents are mineral spirits or benzine and the binders are linseed oil or alkyd resins. These coatings tend to become hard and rigid when they're dry, they don't breathe well and the surface will chalk and become brittle over time. They dry slowly, usually taking at least 12 hours to touch and 24 hours before another coat can be applied.
Below is a list of household paints including some technical information about each and some do's and don'ts for using them, to help in choosing a coating.
This is the "new oil-base", made using alkyd resin in the place of the linseed oil traditionally used to make these coatings. Alkyd dries faster than oil and has low odor in comparison. This coating produces a hard shell finish and is very resistant to wear and fading. It tends to become brittle over time and the surface will product a chalky powder that must be washed off before new paint is applied. Cleanup with mineral spirits or turpentine.
- -interior trim molding, walls and ceilings
- -exterior wood trim molding, wood siding
- -use of bare aluminum, a chemical reaction with salts in the aluminum will cause the bond to fail
- -use over latex, it becomes brittle as the latex remains flexible, causing the alkyd to peel
- -use on bare galvanized metal, it will react with the zinc in the galvanized coating, causing it to peel
Enamels are special coatings designed to create a smooth, hard shell that will withstand wear and hold its finish. Interior and exterior enamels are available in both oil and latex formulas and specially made enamels can be found for many different surfaces including wood, masonry, metals, kitchen appliances and more. Always use enamel for trim molding and consider it for walls where heavy traffic is expected.
- -interior trim molding, walls
- -metal tools, appliances, masonry floors, radiators
- -use just any enamel for any surface, stick with the recommendations on the label
- -use on bare surfaces without first applying an enamel primer
These are two-part coatings that are mixed on site just before using. The coating pigment mixes with a hardener and must be used right away before it sets. Also called catalytic coatings, these dry and harden due to a chemical reaction rather than through evaporation. These have excellent adhesion and a hard finish that resists wear. Epoxies emit hazardous fumes as they harden and should only be used with plenty of ventilation. They tend to chalk and fade over time when uses on exterior surfaces. Check the label for solvent recommendations.
- -painting ceramic, porcelain, fiberglass, plastics and other similar non-porous surfaces
- -re-painting over epoxy
- -apply over other types of paint coatings
- -mix more than you can immediately use
Glaze is a translucent liquid that mixes with colorant to create a see-through finish. It is used for faux finishes such as wood graining and sponging. Glaze dries slower than paint, allowing time to manipulate the finish to create different effects. It is available in alkyd-base and latex. See Painting Glaze and Faux Techniques for more.
A very fast drying coating used mainly on furniture for a hard, glossy finish. It's usually applied with a spray but there are also slow-drying brush-on formulas available. Lacquer should not be applied over other types of coatings as it tends to soften them much like a paint stripper, other coatings can be applied over lacquer, however, with proper preparation. Thin and cleanup with lacquer thinner.
A water-based coating made with acrylic and vinyl binders that fuse together as it dries, creating a film that remains flexible over the life of the finish. While acrylic and vinyl are both used to make latex paint, the best of these is acrylic for improved adhesion, coverage and resistance to fading and mildew, these advantages mean acrylic latex requires less maintenance and repainting.
For breathability latex is the best coating to use on bathrooms, kitchens, exterior siding and other surfaces that see a lot of moisture as long as a good oil primer is used on bare surfaces. Because it allows water vapor in the air to pass easily it doesn't tend to check and peel with normal environmental conditions. Thin and clean up with water.
- -all surfaces around the house except iron and steel
- -apply outside when temperatures will fall below 50° within 48 hours
- -cover with an oil or alkyd coating, they will peel
- -apply shiny finishes without priming first
- -apply over oil or alkyd without washing first
This paint is made using linseed oil as the vehicle and has been mostly replaced by alkyd because of its lower odor. It tends to chalk off with exposure to the elements, creating a powdery residue on the surface that must be washed away before re-coating. It also doesn't breathe well and will tend to block moisture passing through wall surfaces, this can result in checking and peeling. Oil tends to becomes brittle over time making it a poor choice for coating over latex which remains flexible, this can cause the oil top coat to peel as the latex moves and the oil doesn't. Thin and clean up with mineral spirits or turpentine.
Oil and alkyd paint is getting harder to find from local suppliers. Because these paints go through a chemical reaction during the whole life of the coating, they emit volatile organic compounds or VOC's into the environment constantly. The federal government is in the process of implementing new regulations concerning these toxins which will change the way solvent-borne coating like oil-based paint are made. It's still possible to find traditional oils and alkyd paints however.
- -interior trim molding and walls
- -exterior trim molding and siding
- -re-coat with latex without washing first
- -use over latex, it becomes brittle as the latex remains flexible, causing peeling
Choosing Your Paint
When choosing a coating for your project the first consideration is whether the surface you're dealing with is inside or outside. Some coatings are made for both situations, but most will be specific to one or the other. It's best to use paint designated exterior, outside and interior coatings, inside. Exterior products may contain toxic chemicals that are a serious health hazard when used inside and interior coatings used outside will not stand up to harsh weather conditions.
Beyond location, the surface type should be considered. While a general purpose paint can be used in many situations, some surfaces require a specialized coating. For instance, steel and iron will require an oil paint with lots of red oxide to inhibit rust in the finish, and wood moldings will need an enamel to produce a hard, smooth finish that will stand up to heavy traffic and resist fingerprints and smudges.
Finish refers to the luster of a coating, household finishes include flat, eggshell (also called matte and satin) semi- and high-gloss. Finish is an important consideration that will have a significant impact on your paint job. It's true, the prep work is the most important part of painting, but the choice you make for finish can dramatically affect the amount of prep needed and the degree of difficulty in application to get the professional looking job you want. For instance, because shiny finishes like eggshell and semi-gloss tend to show flaws in walls and other surfaces, flat can be a better choice because it tends to hide rough spots. Flat has other advantages over the shinier finishes, it is self-priming over wall repairs, it's very easy to touch up later to hide smudges and stains and it tends to resist roller and brush marks.
Other characteristics of shiny finishes that make them more difficult to use than flat is the need to prime over bare spackle and joint compound before using them. If not primed, these areas will show through the shiny finish when it dries. In addition, care must be taken when rolling or brushing shiny finishes to use continuous strokes, any stopping and starting in the middle of a wall will show when it dries. Of the shiny finishes, high-gloss is the most difficult to use, it shows even the most minor flaws and it doesn't cover very well, requiring multiple coats to do a good job. For these reasons few people use high-gloss on household surfaces.
This doesn't mean shiny finishes don't have their own advantages, they are used because they tend to repel smudges and stains on trim molding as well as to resist stains on bathroom and kitchen walls and ceilings. They also tend to be more durable than flat because of they contain more binders that make the paint adhere better and retain its color to resist fading. When you want to accentuate a feature like crown molding or other, intricate woodwork a shiny finish is an excellent choice.
Color becomes an important consideration if you're making a radical change to the original finish or you plan to use red or yellow as your finish color. A major change of wall color, especially if you're planning to lighten a dark shade, will require at least 3 coats and maybe more to cover completely. Using bright colors will also affect coverage, bright reds and yellows for instance, can require many, many coats to cover completely. These colors get their bright appearance because a neutral base is used. A neutral base has no extra pigment added that would dull the color. This makes the paint more transparent and not good for hiding the surface below. If you must choose a red or yellow, try to use one that's not so bright. For instance, adding a dark pigment like umber to red or yellow creates earth tones leaning toward rust or olive. These dulled versions will cover much better than the pure, bright red and yellow tones. The store clerk can tell you if the color you choose is a "low hide", with a neutral base like this.
Paint quality is important for good coverage, having a significant impact on the work load with regard to the number of coats needed to hide the surface below. Using the best product a brand offers will make coverage much easier. It can take as many as four or more coats of some low grade paints to cover completely even with a minor color change, while a quality one will often cover in as little as one coat. A quality paint will also be more durable and fade resistant than the cheaper options.
Paint quality is determined mainly by the percent of solids it contains. Solids include the binders and the pigment, these are what are left on a wall after the solvent has evaporated. Acrylic and vinyl, usually used in combination, are the most common binders found in house paint, with acrylic being the more durable and flexible. For top quality and performance a 100% acrylic is the best choice. While it will cost a bit more than the other products in a manufacturer's line, the extra work saved will more than make up for the price. In addition, 100% acrylic will last longer, retain its gloss better and resist mildew and color-fading better.
Mixing Leftover Paint
If you want to mix coatings to change colors or salvage leftovers be sure to only mix like coatings together. Don't for instance, mix latex with alkyd or oil-based. Don't mix shellac-based products with latex, oil or alkyd. You can mix oil and alkyd coatings together in a pinch, but it's better to avoid it if the finish quality and durability is important.
It's OK to mix different finishes together such as mixing flat with semi-gloss, the flat will dull the semi-gloss to make an eggshell finish. Or you can add flat to high-gloss to get a semi-gloss finish. When mixing several shades of paint together the resulting color will be some shade of gray, to change it to get a specific, desired color, use the rules of color mixing here.
Working with Oil Coatings
Working with alkyd, oil and shellac-based coatings can get very messy and the risk of ruining surrounding surfaces is high. There's also the issue of cleaning tools and other surfaces after the job is done. In addition, some jurisdictions have strict rules about using these toxic products, even banning them in some cases. All this makes it tempting to forget about using oil altogether. This is not a good idea for some surfaces unless you want to be doing your paint job over again in a matter of a few months or sooner.
To minimize cleanup and make oil coatings easier to deal with try these tips. First try to do all the necessary work at one time. This will eliminate the need to cleanup more than once. If that's not possible use a plastic trash bag and seal the wet tools inside while waiting to continue working. A paint tray and roller can be inserted into a large trash bag and the opening tied shut for a day or more before it starts to dry. Keeping the bag in a cool place with little air circulation will also help to slow drying. Try putting the whole thing in a large cooler or other air tight container.
Use a dedicated brush to apply water resistant coatings and leave the brush in the can when you're done. It will not need cleaning and will be there the next time you need to use it. Some brush handles will be short enough to fit nicely into the average paint can, otherwise, the handle can be cut to a length that will work. When you need to get the brush out of the can again, do it slowly, wiping the excess paint off with a rag and scraping it off on the edge of the can. Then clean the handle with a little solvent before beginning work.
For final cleanup wipe all leftover paint from the roller tray into the can and let the remainder dry on the tray. Hang the tray somewhere to dry so it can be used again later. If you must clean your brush, let it stand in a bucket of solvent for several days before trying to clean it completely. Then use a small amount of solvent in a coffee can or other small container and rinse the brush by bouncing it on the bottom several times before squeezing out the solvent. Pour the used solvent into a re-sealable container and repeat rinsing the brush in the coffee can and pouring off the solvent after each time. When you're done, close the container with the used solvent and let it stand, undisturbed for several weeks. The paint will settle to the bottom of the container and the solvent can be poured off and used again.
About Primers and Sealers
Primers are special coatings designed to bond to bare surfaces creating a sound foundation for a finish paint. A sealer is a special primer that is absorbed into porous materials like wood or masonry to make them water-repellent. In addition to these, a combination primer/sealer is also available for blocking problem stains like smoke and water damage.
A sealer may be clear or it may have a white pigment added. Clear sealers are used for a natural finish on wood, brick, concrete and stone. Pigmented sealers are intended to go under a paint coat to guard against stains that may bleed from a surface through the finish. For example, any painted surface that has been damaged by water should be sealed to block the stain before any repair and re-coating is done.
A primer should be used any time you have a bare surface to paint. In fact, priming is one of the most important things you can do, aside from being sure the surface is clean, to ensure a lasting job. Primers are made to bond to both the substrate and the finish applied over them. To take advantage of this quality the top coating should be applied within a couple days of priming, after this time the primer tends to loose its effectiveness and would need to be applied again for the best possible result.
In general, different kinds of materials require different kinds of primers and some require a special coating, as with rusty iron, for a successful paint job. In addition, exterior and interior surfaces will require a product appropriate to those locations. Previously painted surfaces do not require priming if the existing finish is in good condition, but when peeling exposes bare wood, metal, etc., "spot-prime" these areas before finish coating.
Which Primer is Best?
So what is the best primer to use? It depends on the surface and the conditions it's under, i.e. inside or outside, damp or dry. Wood, whether inside or out should be coated with an alkyd or oil primer. Latex is not a good choice here because of the moisture issue. Wood will absorb and expel moisture through the pores constantly as the atmosphere changes. This is particularly true outside where rain and humidity, sun and wind affect the moisture content in the wood. If you use a water-based coating it will lose it's bond with the wood as the moisture moves in and out, causing it to peel off and take the top coat with it.
On newly finished drywall surfaces a high-build drywall primer is a very good choice if you have a lot of area to deal with and the joint compound has pits and scratches in the surface. These are made to fill in and level the little imperfections making them virtually invisible and it provides a good thick base coat making the finish paint cover easier. If, on the other hand, your joint compound finish is very smooth a standard drywall primer will do just fine, it tends to be a bit cheaper and thinner and spreads easier to seal the porous surface but it does require a thick finish coating for good coverage.
If you are only doing a drywall patch or other small space you don't need to buy a separate product to prime it, a general purpose latex primer or the flat latex you are using to touch up the patch will do just fine.
Plaster can be primed with latex or oil, but oil will do a better job of blocking stains that will often be present in old plaster. Latex is not a good choice when drywall or plaster has been wet. It will allow water stains to bleed right through and will not block other, residual contaminants that the water leaves behind. This can cause stains and bonding problems with repair compounds and finish coatings. Therefore an oil or shellac-based coating is required to prepare a water-damaged surface for repair and painting. Don't use oil on bare drywall, it will cause the paper fibers to bristle, creating a rough texture on the surface that's impossible to remove completely.
There are a couple of manufacturers that are now making paint that is both primer and finish coat in one. Is this a good idea? The jury is still out on this question but real life experience would indicate that a combination coating like this is not a good idea. A search of the internet will return many examples of these products failing to deliver the promised results. The whole idea of primer is to bond with the substrate surface. Finish paint on the other hand, is used to create a protective shell over a surface and it typically doesn't bond well to shiny or slick surfaces. To expect that one paint can penetrate and bond to a surface and give you a uniform, smooth finish, all in one coat is just overly optimistic, even with two coats. So if you want your paint job to last you should always cover bare surfaces with a real primer. Even using a so called all-in-one, and doing two coats, will not be the same as doing the job with an appropriate primer and following with a good finish coating.
a latex coating used to bond to usually un-paintable, slick surfaces like pvc, fiberglass, ceramic tile, glass and laminate.
is specifically made for new drywall. There are two types, standard drywall primer which is thinner and usually a little cheaper and high-build drywall primer made to fill in little imperfections like pits and scratches in joint compound.
used mainly on trim molding as a good foundation for an enamel finish because it tends to level and smooth the surface. Easily sanded between coats and bonds well with finish paint. Usually alkyd-based although latex is also available but it typically doesn't stand up as well. Alkyd should always be used under an oil or alkyd enamel top coat, but it will improve the finish of latex enamels as well.
Galvanized Metal Primer
is used on bare galvanized steel and then a compatible top coat is applied. It is recommended to use a primer and top coat made by the same manufacturer specifically for galvanized surfaces. Because galvanized metal is a specially treated material, it requires a specially formulated primer and top coat made to work together. These may be hard to find in home stores, but they will be available at a paint store.
may be interior or exterior and used for drywall, plaster, wood, aluminum, masonry and generally any surface except steel and iron. This is not very durable and will not work well on exterior surfaces as it tends to lose its bond when water comes in contact.
is clear and made especially for bare masonry especially brick where a natural finish is desired. If the surface is to be painted, a latex primer will do the job. Allow at least 1 month for new masonry to cure before priming or sealing.
very water resistant, Kilz® and Zinsser® BIN are two common brands you will find from local suppliers. An excellent choice for virtually any priming requirement except bare drywall. One of these should always be used for exterior wood surfaces instead of latex to prevent peeling due to water contact.
this is the best sealer you can use to block stains like water residue, rust, smoke and grease. It should be used to seal surfaces before repairing water damage to walls and ceilings. Oil primers work for this too, but if there's any concern about a particularly robust stain, you should use a shellac-based sealer for the best results. Zinsser® makes a shellac primer like this. It is quick drying and can be top coated in about an hour. Cleans-up with denatured alcohol. Because the solids in this coating settle out quickly, make sure to shake the can or stir it well just before using it. To avoid breathing the harsh fumes provide plenty of ventilation and wear a painter's respirator when using it inside on large surfaces.
are for iron and steel surfaces. These are usually red in color and contain red oxide pigment. Stopping rust formation after it has started is hard to do and will sometimes be impossible. Before apply a rust inhibiting primer to rusted metal, first remove all the loose rust and treat the area with naval jelly or a rust converter for the best possible result. See Stopping Rust for more.
are generally a poor choice for most sealing requirements because they don't stand up to water well. However, they are better for containing the tannin in redwood that can bleed through alkyd and shellac-based coatings.
About Wood Bleach
Bleaching is a process used to lighten wood color or to remove stain damage such as water or urine. There are basically three types of bleach used for these purposes: chlorine, oxalic acid and peroxide. Each of these is used for different types of situations and different types of stains.
When using one of these wear rubber gloves, eye protection and remove any wax or varnish from the surface before attempting to bleach out stains. The bleaching process will raise wood fibers so sanding will be necessary to smooth the surface after it has dried and before refinishing.
can be used for lightening a dye-based stain without changing the natural color of the wood. Dye stains are used to change the color of wood finishes but when you want to reverse this effect, a chlorine bleach will usually do the trick. These are available in different strengths from laundry bleach to pool sanitizer. Laundry bleach will work for this but use a pool bleach for the quickest and easiest results. These are available in a powdered form and are mixed with water just before applying.
Along with the usually hand and eye protection, wear a dust mask when using this chemical. Mix the powder into the water until no more will be absorbed and then apply the solution liberally to the wood. If the stain immediately lightens to your satisfaction, rinse it off with water and let it dry. If the stain remains, let the bleach sit on the surface, overnight if necessary until it lightens to your satisfaction. If the stain doesn't lighten enough, try a second application. Some dye stains may lighten completely with this treatment and some may only lighten to a certain extent.
- Works on Dye-Based Wood Stain
- Also removes: grape juice, tea and coffee stains
- Neutralize with distilled water
is used to remove water stains from wood and in deck cleaners to brighten graying. Wood is stained by water when it reacts with the tannins, leaving black and gray stains. Mix the oxalic acid crystals with hot water until no more will dissolve and apply the solution evenly over the whole area. Let the acid dry and apply another bath if necessary, if the stain remains after the solution dries apply another until the stain is gone.
Let the acid dry completely and then remove the residue with several rinses of distilled water, followed by a rinse with a baking soda and water solution to neutralize the acid.
- Works on Wood Water Stains
- Also removes: some blue and black inks
- Rinse with distilled water and neutralize with baking soda solution
is used to lighten a natural wood color. This is a two-part bleach using sodium hydroxide (Part A) and hydrogen peroxide (Part B), these two chemicals will only work to lighten wood when they are combined. The two parts can be mixed and then applied, or used one immediately after the other to optimize the potency of the bleaching effect.
When the two parts are mixed together the strength of the bleaching action dissipates very quickly. This makes it necessary to mix them just prior to applying and working very quickly to take full advantage of the bleaching effect. A better approach is to saturate the wood with Part A and then immediately follow with Part B to maximize the potency. Don't let the first solution sit on the wood too long before using the second, this may cause some woods to darken when the sodium hydroxide reacts with the tannins. One application is usually sufficient to lighten most woods but a second may be necessary to even out the finish color.
- Works to Lighten the Natural Wood Color
- Also removes: some pigmented stains
- Neutralize with vinegar and distilled water solution
About Wood Stains
Wood stains come in two basic types: pigmented and dye-based. These affect the color of wood grain in different ways, pigmented stains sit on top of the wood surface to coat it with a new color, dyes soak in and penetrate the pores to change the wood color from within.
Apply wood stain with a brush or rag and let it seep into the wood, after a few minutes, wipe the excess from the surface. Another coat can be applied to deepen the color. Most wood stains will require a clear protective coating when dry to finish the job, an exception to this is a stain and varnish in one that is made to serve both functions.
are made much like paint using binders to hold the pigment to the wood surface after it has dried. Because the pigment sits on the surface of the wood and doesn't soak in, it's best to have a semi-rough finish to grab and hold the color. For this reason these stains tend to produce an uneven finish adhering better to small nicks in the surface and not as well to the smoother areas.
Pigmented stains are available in oil and water bases. Oil stains tend to work better because they don't evaporate as fast and won't raise the wood fibers like water-based stains will. Oil stains are more toxic and require mineral spirits for cleanup, water-based stains can be cleaned up with soap and water.
are absorbed into the cells of wood to change the color, this makes for a more natural looking and even finish than can be achieved with pigmented stains. These stains come in two forms: powdered dye that mixes with water and a premixed solution of alcohol and dye. The powdered dye can be mixed in varying degrees to make deeper tones or to match a stain color.
are a mixture of oil stain and varnish resin intended to be a one-step wood finish. While these may save time and effort they do not produce a smooth, hard finish like traditional varnish and several coats are required for durable protection of the wood.
About Clear Coats
A clear coat is used to protect a painted, stained or natural wood finish and can be either an oil, a varnishes, or a blend of the two. Oils like linseed and tung oil can be used to build up a hard, protective finish, but to achieve this takes several applications that must dry completely between coats, and because the drying time can be as much as several days for each coat, it can take a very long time to complete the job. Varnish can do the same job with one coat and in a short period of 12 to 24 hours.
Oil finishes are made by pressing linseed or tung tree nuts to extract the fluid which can then be applied as a protective finish. Varnish and shellac are made by dissolving a plant or insect resin in solvent to make a spreadable fluid. After the coating is applied, the solvent evaporates and the resin remains to form a hard, smooth, protective finish. Some clear coats harden almost immediately after the solvent evaporates, others remain soft for a curing period before becoming hard. Exposing any of these to heat or sunlight will speed up the curing time.
Clear coats are usually completely clear but some, like orange shellac, will add a slight color to the finish. Clear finishes should not be shaken before applying, this would create air bubbles in the coating and in the finish, instead stir the coating gently just before application.
this is a water-borne clear coat with lower odor than solvent-borne varnish. Like polyurethane, acrylic is not absorbed and tends to sit on top of wood surfaces forming a hard shell. Acrylic cleans up with water and resists yellowing and UV damage.
this is a "modern" varnish made using plant-based oils dissolved in mineral spirits. Other ingredients are added to the mix to improve the durability and gloss-retention of the finish coat.
this is a wood finishing liquid made with linseed or tung oil and usually some pigment added for color, there is no solvent involved. This is a one-step wood finish that penetrate and dry quickly to a low-luster. An added advantage of an oil finish is that a clear protective coat is not required, in addition danish oil can serve as a first coat under an oil stain or paint.
Epoxy Clear Coat
this is a two-part coating that should be mixed just before application. These can't be stored, having a pot-life of a couple of hours, they must be applied immediately before they harden.
this is a very quick-drying, hard, clear coat typically used to finish furniture. Lacquer is made by dissolving lac beetle secretions in lacquer thinner, interestingly, shellac is made by dissolving the same resin in alcohol. Because lacquer evaporates so quickly it should be applied by spray for an even finish. In addition, lacquer is very flammable and should be used only in a controlled environment to avoid combustion.
Unlike other clear coats, lacquer and shellac remain soluble over the life of the coating and can be damaged or removed when the finish comes in contact with the original solvent or thinner containing elements of the original solvent.
A urethane-based clear coat that can be used in place of oil or alkyd varnishes. Polyurethane is not absorbed into the wood and over time it tends to separate from the surface causing blisters under the coating. This separation will be encouraged with impact or heavy pressure from furniture legs, making polyurethane a bad choice for floors unless it is "oil-modified" to make it more durable.
Polyurethane is not a good choice for exterior use because of it's extremely vulnerable to ultraviolet sunlight. UV absorbers are added to help mitigate this effect but even with these a polyurethane coating will not last when used outside.
this is made by dissolving lac beetle secretions in denatured alcohol. Fast drying and versatile, shellac can be used as a clear coat finish as well as a primer/sealer on interior surface. Shellac has long been the preferred finish for furniture and comes in two basic types: clear and amber or "orange shellac". Because it is vulnerable to water it should not be used where moisture may be a problem. Pigmented shellac is often used as a primer/sealer to block stains from ink, smoke, water, grease and food as well as to seal knots and sap in wood.
this varnish originated as a coating for the spar mast on ships. Its primary qualities are an ability to resist moisture and to remain flexible with movement, as with a spar. Spar varnish is not typically glossy and therefore not used for its appearance, but where protection of surfaces exposed to weather and movement is the main goal.
made from the tung tree, 6 or 7 coat of this oil can be used to build up a hard clear coat. Because it must be sanded between coats and each coat can take up to 3 days to dry, most people aren't inclined to use it. Products label tung oil available from local suppliers is not true tung oil but a thinned down varnish. These can be used just like Danish oil.
About Thinners and Solvents
A solvent is a fluid used to breakdown and dissolve paint and varnish. The solvent is mixed with paint binders and pigment to make a liquid coating that can be easily applied to a surface. Because the solvent evaporates as the paint dries, it is essentially a delivery system for the coating. Different types of paint coatings require different solvents for thinning and cleanup.
Most paints are intended to be used straight from the container, further thinning is usually not required or recommended. However, when it has been exposed to air for some time, thinning may become necessary to restore the viscosity of the coating. In addition, some oil or alkyds may "drag" when applied straight from the container and therefore will require thinning to make application easier. When using a sprayer, thinning will be necessary to increase the viscosity of the coating so it will pass through the equipment and onto the surface. Below is a list of thinners and solvent for the most commonly used household coatings, use the same product for cleaning equipment and spills.
this is a strong solvent used mainly for cleaning purposes. It can be used to dissolve superglue, nail polish, epoxies and spray foam insulation. Use a soaking bath to remove old paint from metal hardware. See these tips for restoring decorative hardware for more. Care should be taken when using acetone as it will dissolve many finishes on walls, trim and furniture. Nail polish remover contains a high level of acetone and may be used as a substitute in a pinch.
used as a solvent for shellac, some dye-based wood stains and shellac-based sealers. Denatured alcohol can be used as a fuel and to clean and purify many surfaces before applying adhesive. Also very effective at removing ballpoint ink stains. Because rubbing alcohol is about 70% denatured alcohol it may be used as a substitute, in a pinch.
use this product to speed drying of oil and alkyd products. Because it shortens drying time significantly the coating must be applied quickly. Only a small amount should be used to avoid altering the color.
used to dissolve lacquer paint. This solvent is very effective for removing ink stains from many surfaces and dissolving old paint from metal hardware when a soaking bath is used. Care should be taken when using lacquer thinner as it will dissolve many other finishes like ink, paint and furniture varnish. Both lacquer coatings and lacquer thinner evaporate very quickly and are highly flammable, avoid open flames and long exposure to fumes.
petroleum-based solvent used to thin alkyd and oil coatings. This may also be called white spirits or just paint thinner. Because it is virtually odorless it has replaced turpentine for this purpose.
this is a solvent derived from pine trees and used to make oil paints and varnishes. It has been replaced by mineral spirits for cleaning and thinning because the high odor makes it undesirable in most situations.
used to clean up and thin latex paint and other water-based coatings.
Which Paint for Household Surface
The following is a list of commonly painted surfaces and the coatings best suited for each.
Wash any chalky powder from the surface before finish painting with an acrylic exterior latex paint. On bare aluminum use an exterior latex primer. Don't use alkyd over bare aluminum, a chemical reaction will cause the coating to fail.
Prime unglazed brick with a latex or masonry primer and finish coat with a latex paint. Use a clear masonry sealer for a natural finish. Glazed brick has a hard smooth finish that will not hold a latex finish, use an adhesive primer or epoxy paint.
A faux finish can be applied to interior ceramic surfaces that won't see a lot of wear. Coat with an adhesive primer on ceramic tiles, etc. and then finish coat with an oil finish. There are also epoxy paints made for ceramic but they are harder to use.
Use a rubber-based paint to prime and finish coat cinder block. Elements in the block structure will cause it to reject all other coatings. Cinder block coatings my be hard to find at home stores but a paint store will usually have this product.
Allow new concrete to cure for at least 28 days before coating. Etch concrete floors with an etching product or muriatic acid (available from hardware stores) to clean and open the pores before coating with a paint made for concrete floors. Follow all label directions and observe these cautions and best practices when using muriatic acid. Whatever etching product you use, wear protective clothing, a respirator, and safety goggles to avoid contact with splashing acid.
Prime new drywall with a drywall primer or flat latex paint. A high-build drywall primer should be used to help hide new joint compound seams that have pits and scratches in the surface. Finish coat with any latex or alkyd-based coating. Never use alkyd or oil-base on bare drywall, it will raise the paper fibers and permanently ruin the drywall finish.
Exterior Wood Siding
Prime with an exterior oil or latex primer. Finish with latex or oil finish coating but don't use oil over latex primer or old latex finish paint.
Remove rust first with navel jelly and coat with a metal primer containing red oxide to help inhibit future rusting on iron and steel. Always use an oil or alkyd-based finish to repeal water on metal surfaces, the water in latex will encourage rust to form.
As a general coating, acrylic latex paint will usually adhere well to galvanized metal. There are a few specialty paints that will also work, see a list here. For the best results use a primer and paint made specifically for galvanized steel.
New galvanized metal for exterior uses has an oil coating that will repel any new coating. This oil must be removed using mineral spirits before any paint is applied. Clean residue left from the solvent using soap and water and let it dry before priming. The metal may be coated with a primer and top coat containing zinc. These bond with the zinc in the galvanized coating to create a durable finish. Other paints, with a few exceptions, will not bond with the zinc and peeling will result. It is recommended to use a primer and paint combination from the same manufacturer as these are designed to work together.
Glass is not usually painted but if a faux finish is to be applied use an adhesive primer. Wipe the surface with denatured alcohol before priming and then finish with any paint or glaze.
New masonry will require a curing time of about 1 month for the alkali to wash out before a coating is applied. Prime with a latex masonry primer and then use a latex paint to finish coat. Use a long nap roller and go over bare masonry repeatedly for good coverage. A slightly damp surface will make application easier on bare masonry.
Medium Density Fiberboard, use to make trim molding for interior applications. Use an oil primer and sand after it dries and before applying a finish coating of oil or latex enamel.
New plaster of paris must cure for 6 months before any coating is applied. Most modern wall repair compounds don't use plaster of paris so there's no need to wait before painting. Prime water-damaged plaster with an oil primer-sealer to block stains before repairing. Prime new wall patches with an oil and finish coat with any latex or oil coating.
Use specifically made coatings for plastic on outdoor furniture and other surfaces that see a lot of wear. Use an adhesive primer for plastics where a faux finish or other coating will be applied.
Prime with an adhesive primer and finish coat with any latex or oil coating or faux finish glaze.
Use a product made specifically for vinyl siding and don't use a dark color that will absorb a lot of sunlight. This will cause the surface to heat up and the vinyl to warp and pull away from the house.
Prime simulated wood paneling with an adhesive primer. This will ensure a good bond to the slick finish of most simulated wood. On natural wood paneling use an oil primer after a light sanding. Finish coat with any latex, oil or alkyd finish.
Wood Trim Molding
Prime bare wood with an alkyd enamel undercoat, then use latex or alkyd enamel as a finish coat. You could use a latex undercoat but for the most durable finish an alkyd works best.