Tuesday, May 6, 2014

Surface Preparation Hand Tools 02 -Painting and Decorating-02


If using oil based paint pour solvent into a paint tray and stroke brushes or rollers back and forth until the solvent dripping from them is clear. Moreover the oil based paint can be cleaned from the tools by using
White spirit
Turpentine and substitutes


White spirit also known as Stoddard solvent or mineral spirits, is a paraffin-derived clear, transparent liquid which is a common organic solvent used in painting and decorating. It is a mixture of aliphatic and alicyclic C7 to C12 hydrocarbons with a maximum content of 25% of C7 to C12 aromatic hydrocarbons. It is a mixture of aliphatic and alicyclic C7 to C12 hydrocarbons with a maximum content of 25% of C7 to C12 aromatic hydrocarbons. White spirit is the most widely used solvent in the paint industry. In households, white spirit is commonly used to clean paint brushes after decorating. Its paint thinning properties enable brushes to be cleaned (by preventing the paint from hardening and ruining the bristles), enabling them to be reused.

Turpentine substitute, also known as Mineral turpentine is an inexpensive petroleum-based replacement for the vegetable-based turpentine. It is commonly used as a paint thinner for thinning oil-based paint and cleaning brushes, and as an organic solvent in other applications.
Mineral turpentine is a hydrotreated light distillate of petroleum, and consists of a complex mixture of highly refined hydrocarbon distillates mainly in the C9-C16 range. The material is a colourless transparent liquid at room temperature, and immiscible to water. The liquid is highly volatile and the vapours are flammable. It can be a very dangerous inhalant.
Mineral turpentine has a characteristic unpleasant odour. Chemical manufacturers have developed a low odour version of mineral turpentine which contains less of the highly volatile shorter hydrocarbons.
The water based paint can be cleaned from tools using cold water. Remove water based paints with soap and wearer, working the bristles or nap until the water runs clear.


When brushes and roller cover are clean, use a spinner tool to remove excess solvent or water. Make sure to wipe clean and dry. When the tools are dry return them to the original wrappers and hand securely separately.

Oil-based (also known as solvent-based) coatings, such as paints, stains, and varnishes are amongst the oldest organic coating materials; in China, they have been known for more than 2000 years. Oil paints consist natural drying oils (e.g. linseed  oil, China wood or tung oil, and soybean oil) which undergo autoxiadative polymerization in the presence of catalytic dries and atmospheric oxygen. Further constituents may include hard resins that general react with the drying oils at elevated temperature (230-2800C) to form oleo resinous binders. On account of the air sensitivity of the oils, heating mainly takes place under an inert gas atmosphere.
Conventional dispersion equipments (e.g. ball, roller or sand mills) are suitable for producing oil paints.

Oil based coatings are relatively environmentally friendly as long as hazardous solvents and toxic pigments (e.g. red lead or zinc chromate) are not used. The oil used in such paints have a low viscosity. They are therefore particularly suitable for priming coas o manually derusted steel surfaces since they wet and penetrate the residual layers of rust well, resulting in thorough coverage.
Oil based coatings are easily applied by conventional methods (e.g brushing, roller coating, spraying and dipping)
Oil-based coatings contain resins, solvents, pigments and additives. These coatings are harmful
to the environment because they contain petroleum distillates and pigments which, when
evaporated, can increase volatile organic compound (VOC) levels in the air.

Oil-based coatings can have adverse effects on your health if not used properly. If used in poorly
ventilated areas, the vapors from these products can irritate eyes, skin, and lungs, causing
headaches and nausea. The vapors can also contribute to respiratory problems, muscle
weakness and liver and kidney damage.

Oil-based coatings can also harm the environment if not disposed of properly. Never pour paint
down a storm drain or sewer system. This can pollute groundwater, rivers and streams.

Water based paints are synthetic resins and pigments, plus coalescing agents, that are kept dispersed in water by surfactants. They dry by evaporation of the water, the coalescing agents cause the particles of resin to fuse together as the water evaporates to form a continuous coating.  It has a binder that is dissolved in water. In general, water-based paints are less toxic and contain fewer volatile organic compounds (VOCs) than solvent-based (also called oil-based or alkyd) paints. It is also known latex paint.

water based paints are based on acrylic, urethane, polyvinyl acetate (PVA) or epoxy dispersions. Acrylic emulsions are used in exterior applications where their non-yellowing characteristics as well as excellent weatherbility are outstanding. Water  based urethanes are suited to uses where good flexibility and toughness are important , such as leather and polymer coatings, but their major drawback is their high cost. PVA and epoxies give good weathering resistance. Water based paints take longer to dry than many organic solvent based paints, and give a surface finish that is less good.

Water based paints must be protected from freezing and applied at a minimum temperature of 10 c. humidity and temperature control are critical for the drying time. A heat cure is sometime necessary. Pigments must be compatible with water. Metallic particles are usually coated before being mixed into the paint to prevent chemical reaction with water. Many conventional binders (alkyls, acrylics and expodies) can be made water soluble by chemically attaching polar groups such as carboxyl, hydroxyl and amide. Dispersions are very small particles of binders, less than 0.1 microns diameter, dispersed in water. Emulsions or latex differ from dispersions by having much larger particle sixe on the order of 0.1 micron or more. They are made by precipitation in water and therefore do not need to be dispersed mechanically.

Saturday, May 3, 2014

Surface Preparation Hand Tools 01 -Painting and Decorating-01


Proper surface preparation is essential for the success of any protective coating scheme. The importance of removing oil, grease, old coatings and surface contaminants (such as mill scale and rust on steel, laitance on concrete and zinc salts on galvanised surfaces) cannot be over emphasised.

The performance of any paint coating is directly dependent upon the correct and thorough preparation of the surface prior to coating. The most expensive and technologically advanced coating system will fail if the surface preparation is incorrect or incomplete.

Loosely adhering mill scale, rust and old paint coatings may be removed from steel by hand wire brushing, sanding, scraping and chipping. However, these methods are incomplete, and always leave a layer of tightly adhering rust on the steel surface.

Basic Surface Preparation hand Tools

Scraper
putty knife
dust brush
shave hook
chisel knife
nail punch
filling
knife/spatula




Scraper

A scraper is a single-edged tool used to scrape metal from a surface. This may be required where a surface needs to be trued, corrected for fit to a mating part, needs to retain oil (usually on a freshly ground surface), or even to give a decorative finish.

The task of scraping has been the bane of most engineering apprentices, however its versatility and appropriateness far outweighs the hard work it requires, or is perceived to require. Its effective use requires skill and concentration. An often overlooked advantage of scraping is the ability to take the tool to the work piece. When the work piece weighs several tons and towers over the worker, the apprentice's solution of chucking it on the mill is impractical, if not impossible. A skilled craftsman can wield a scraper and produce work that is the envy of his peers. This takes more time than the usual methods.

Putty Knife
Sometimes referred to as a spackle knife, the putty knife is a scraping tool that is constructed in a manner that is similar to the kitchen spatula. Distinguished by a flat blade that is equipped with a sturdy handle, the putty knife can be used in a number of different construction and home repair projects. Putty knives are available in two distinct types, with each type being geared toward specific applications.

The stiff blade style of putty knife is constructed with a solid metal blade that is somewhat thick and does not bend easily. This type of putty knife is ideal for use in any job where there is a need for a rigid tool. One example of a task that the stiff blade putty knife is uniquely suited for is scraping. The scraper action can help to remove paint or wall paper, or as a means of ridding just about any smooth surface from a foreign element.

Dust brush
It is a tool with bristles wire or other filaments. This can be used to keep surfaces clean and free of debris. It generally consists of a handle or block to which the filaments are affixed either parallel or perpendicular, depending on the way the brush is to be gripped during use.







Shave hook
It is used for cleaning and preparing lead cable sheath and sleeves for soldering and wiping joints.
and Consists of a flat hardened steel blade riveted to a shank fitted with a plastic handle. The Blade has a sharp, beveled cutting edge which is circular in shape at one end and is brought to straight sided point at opposite end. Shave Hooks feature hardened and tempered steel blades, riveted to shanks which run through the full length of the specially shaped handle.





Chisel knife
It is a tool for checking the adhesion of the paintings on their substrate.
A knife with a square edge, usually 1 ½ in. (3.8 cm) or less in width, used to scrape off paint or wallpaper in areas where a wider-edged stripping knife would not be suitable. Traditional tradesmans quality tool with one piece through tang tempered stainless steel blade for strength and durability, complete with hardwearing rosewood scales handle.





Nail Punch
A nail punch, also called a nail set, is used to drive the head of a nail flush with or below a surface. A pin punch is a similar tool used to drive pins for affixing a fixture to a rotating shaft. Nail and pin punches have a body by which the punch is held, with a flat ended cylindrical section whose diameter suits the object to be driven.



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