Exterior Semi-Transparent Stains: Latex or Oil Exterior Semi-Transparent Stains: Latex or Oil

Fact: No matter what anyone tells you, wood will not "drink up" the oils in a stain and restore life to the siding. The wood is dead. Coat it for a good appearance and low maintenance with a longer lasting finish.

Semi Transparent Oil Stains are moderately pigmented and, thus, do not totally hide the wood grain. These stains penetrate the wood surface, are porous, and do not form a surface film like paint. As a result, they will not blister or peel even if moisture gets into the wood. Latex (water borne) stains are also available, but they do not penetrate the wood surface as do the oil based stains.

Stains are most effective on rough lumber or plywood surfaces. They are available in a variety of colors and are especially popular in the brown tones since they give a "natural or rustic wood appearance." They are not available in white. They are also an excellent finish for weathered wood. They are not effective when applied over a solid color stain or over old paint.

Semi-transparent Penetrating Stains may be brushed, padded or rolled on. Brushing will give better penetration and performance. These stains are generally thin and runny, so application can be messy. Lap marks will form if stains are improperly applied. Lap marks can be prevented by staining only a small number of boards or a panel at one time. This method prevents the front edge of the stained area from drying out before a logical stopping place is reached. Working in the shade is desirable because the drying rate is slower. One gallon will usually cover about 300 to 400 square feet of smooth surface and from 150 to 200 square feet of rough surface. For long life with penetrating oil-base stain on rough sawn or weathered lumber, use two coats and apply the second coat before the first is dry. Apply the first coat to a panel or area as you would to prevent lap marks. Then work on another area so that the first coat can soak into the wood for 20 to 60 minutes. Apply the second coat before the first coat has dried. (If the first coat dries completely, it will seal the wood surface so that the second coat cannot penetrate into the wood.) About an hour after applying the second coat, use a cloth or sponge to wipe off the excess stain that has not penetrated into the wood. Stain which did not penetrate will form an unsightly surface film and glossy spots. Avoid intermixing different brands or batches of stain. Stir stain thoroughly during application. Sponges or cloths that are wet with oil-base stain are particularly susceptible to spontaneous combustion. To prevent fires, bury them, immerse them in water, or seal them in an airtight container immediately after use. A two-coat wet system on rough wood may last as long as 10 years in certain exposures. If only one coat of penetrating stain is used on new wood, its expected life is 2 to 4 years, but succeeding coats will last longer.

Semi-transparent Penetrating Stains are relatively easy to refinish. Excessive scraping and sanding are not required. Simply use a stiff bristle brush to remove all surface dirt, dust, and loose wood fibers, and then apply a new coat of stain. The second coat of penetrating stain often lasts longer since it penetrates into small surface checks which open up as wood weathers.

Note: Steel wool and wire brushes should not be used to clean surfaces to be finished with semitransparent stains since small iron deposits may be left behind. Pentachlorophenol may cause iron remaining on the surface to corrode. The corrosion products may then react with certain wood extractives to form a dark-blue, unsightly discoloration which becomes sealed beneath the new finishing system. Pentachlorophenol was commonly used in some semitransparent penetrating stains and water-repellent preservatives before it became a restricted-use pesticide.

Unlike paints, semi-transparent penetrating oil-base stains cannot check and peel from plywood surfaces. These stains penetrate the wood and do not form a continuous film or coating like paint. Semitransparent penetrating stains allow most of the wood grain to show through, and the color can be controlled by pigments added to the stain. Penetrating stains also perform well on weathered surfaces. New, smooth surfaces may also be stained. Oil-base penetrating stains have a longer life expectancy when properly applied to rough sawn or weathered surfaces. Semitransparent stains may be brushed or rolled on. Brushing should give better penetration and performance especially on textured surfaces. These stains are generally thin and runny, so application can be a little messy. Lap marks will form if stains are improperly applied. Lap marks can be prevented by staining only a small number of boards or a panel at one time. Working in the shade is desirable because the drying rate is slower. The penetrating stain should be stirred frequently during application. One gallon will usually cover about 300 to 400 square feet of smooth surface and from 150 to 250 square feet of rough surface. For long life with penetrating base stain on rough sawn or weathered lumber, use two coats and apply the second coat before the first is dry. Apply the first coat to a panel or area as you would to prevent lap marks. Then work on another area so the first coat can soak into the wood for 20 to 60 minutes. Apply the second coat before the first coat has dried. (If the first dries completely, it may seal the wood surface so that the second coat cannot penetrate into the wood). About an hour after applying the second coat, use a cloth or sponge to wipe off the excess stain that has not penetrated into the wood. Stain which did not penetrate may form an unsightly surface film and glossy spots.

Note: Sponges or cloths that are wet with oil-base stain are particularly susceptible to spontaneous combustion. To prevent fires, bury them, immerse them in water, or seal them in an airtight container immediately after use. A two coat wet system on rough wood may last as long as 10 years. If only one coat of penetrating stain is used on new wood, its expected life is 2-4 years, but succeeding coats will last longer.

This article has been contributed in part by Michigan State University Extension

Got a New Project You're Proud of?

Post it on Your Projects!