Painting Tips for Spring and Summer
How to Remove Mildew
To remove mildew from a painted surface, wash the surface with the following mixture
2/3 cup trisodium phosphate
1/3 cup detergent
1 quart chlorine bleach
3 quarts of warm water
Rinse the surface well with clean water after washing. Please wear appropriate safety equipment (rubber gloves and eye protection) and…..protect shrubbery and plains with plastic sheeting.
The maximum moisture content for any surface that is to be painted is 12-14%. Painting a surface that contains a higher level of moisture can lead to peeling problems. The only accurate way of determining moisture content is with an electronic moisture meter.
Too Many Coats
There is a limit to the number of coats of paint that a surface can support. As the paint thickness builds up over time and the coatings gets older, they lose their flexibility. As the substrate (surface) expands and contracts because of temperature fluctuations or moisture, the paint film is no longer flexible enough to move with the surface. Cracking or flaking of the coating usually results. It is not uncommon to put a coat of paint on a surface that appears sound only to have many layers of paint peel away. At this point the surface must be stripped.
Efflorescence is a white deposit that forms on masonry surfaces. Moisture moving through masonry will pick up water soluble salts which are left behind when moisture reaches the other side. The moister moving through the masonry can pass through a flat paint, but the efflorescence builds up behind the paint until it causes peeling. To solve the problem, the moisture migration must be stopped first and the efflorescence brushed off, before repainting is done.
Painting with dark colors on a hot day, or in direct sunlight can cause the paint on the surface to skin over and trap solvent in the film. As the solvent tries to escape, blisters can form in the paint. Repair of these blisters requires sanding and repainting.
Wood decks are commonly painted or stained after they have been constructed. After construction, the sides and bottom of the wood cannot be coated properly. Many failures on desk are caused by moisture entering the wood through the sides and bottom. Moisture seldom leaves these structures the way it entered. The sun shines on the coated surface and the moisture tries to come out through the paint or stain which causes peeling. To improve the resistance to moisture, the coating should be applied to all surfaces prior to construction.
Pressure-treated lumber is kiln-dried wood (usually spruce or yellow pine) that is pressure treated with chemical preservatives dispersed in water. To check if the wood is dry enough for stand or paint, put water drops on the surface. If it soaks in, it’s ready. When the wood is dry, it can be painted or stained like any other wood surface. Pressure-treated wood that is not painted or stained will weather, crack, and check as badly as untreated wood over time.
Wood that has been exposed to the sun for more than a month should be sanded before painting – especially if the wood has started to turn grey. Sunlight causes the wood fibers to “chalk” and erode unevenly. They then form a weak surface layer that has poor adhesion to the wood surface, which can cause the pain to peel. To see how much sun damage has been caused to the wood surface, press a piece of tape on the surface, rub the black of the tape to ensure good contact, and then strip off the tape. If there are a lot of wood fibers on the back of the tape, the wood needs sanding before painting.
To avoid lap marks when using exterior stains, try to work in the shade as much as possible. Paint only one or two boards at a time, making sure that the stain doesn't dry in the middle of a board during application. Complete the boards from side to side (horizontal siding), or top to bottom (vertical siding), before moving to the next board).
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