" " wisno wood furniture finishing: Varnish for wood finishing

Tuesday, March 2, 2010

Varnish for wood finishing

Varnish

Varnish traditionally is the finishing material made from the development of the oil finish. Different with oil or wax finish, the varnish can form film layer and can provide better protection to the wood. Varnish is made of drying oil which is mixed and processed with additional resin and some other additives. Resin is the material that will serve to form a film layer. There are 3 types of resins are the most widely used to make varnish that are: alkyd, phenolic and urethane.
Alkyd resin is the most common used to make varnish because of the flexibility and simplicity. Phenolic resin will produce a varnish with harder film layer than alkyd resin. While the urethane resin in the varnish will produce the strongest film, the higher resistant to scratches, chemicals or heat compared varnish with other resin.
The oil that most often used is linseed oil or tung oil. The varnish composition is vary depending on the type and brand of varnish. Varnish that use oil in a large percentage is referred as long oil, it will produce the elastic film layer and more widely used for outdoor finish. While varnish with the smaller percentage of oil will dry faster and widely used for indoor finish.
The mixture of oil and resin then is added a mixture of solvents to dilute the varnish and make it can be applied easily. Solvent used to dissolve the mixture must be compatible with oil and resin used. The most common solvent used is a type of mineral spirits. Then the mixture of varnish is added with some additives materials to produce specific properties desired. Some additive materials that are often added to the varnish are: drier (additive material to speed up the drying time of varnish), flattening paste (the material to reduce and set up the gloss), u.v. stabilizers (material to protect the varnish from ultraviolet light, it is needed for outdoor finish varnish).
The varnish application 
Now the varnish is still widely used and available as the finishing materials. Varnish is used either alone or in combination with other finishing materials. There are several ways apply the varnish according to the finishing requirement and facilities available. 
  • Brushing varnish
Brush the varnish is one varnish applications most commonly used since the early time when varnish is started to be used as finishing material. This application is simple and does not require special equipment and facility. This process is already done long time ago when the spray gun is not available yet. Now brushing varnish still be done in some finishing shop where the finishing room and spray gun is not available. Varnish can be brushed with quite good result. Varnish is a material that requires relatively long time to dry, so the resulting surface can be quite even, with less brush marks.
Varnish with a brush application requires patience and proper technique. Apply a thin application in several times for maximum results. The application that is too thick will tend to produce uneven coatings and will increase the risk of sagging on the film. To obtain a thick film layer the several times application is needed. Usually 3 or 4 times application is needed to built enough film layer. Every new layer must be coat on when the previous layer is completely dry and well sanded.  
Apply 1 or 2 layer of varmint, then let it for about 2 or 3 hour to dry. Sand with # 360 or # 400 stearated sand paper then coat with another layer of varnish. Repeat this process until a smooth and even surface film is obtained.
  • Wiping varnish
Wiping is the other way of varnish applications that do not require special tools and room. Like the brushing application this system application also does not release dust spray to the air, so it does not spray booth. Varnish is padded evenly on the surface by using the rag. This application will produce a more even coating and will not leave brush lines as the application with a brush, but the resulting coating will be thinner than brush application. Varnish is applied by wiping is usually designed a little different and made a little thicker than the varnish is applied by brush As well as the application with a brush, this applications can be done in several times to produce the desired thickness film layer.
  • Spray application for varnish
At this time, the spray system is most widely method for applications finishing materials. Application varnish by spray is also more popular now. Like other finishing material the spray application is most practical, easy and fast with excellent result. The use of varnish as the finishing material now is mostly combined with other modern finishing materials such as stain, glaze other clear coating like nitrocellulose, polyurethane, acid curing or precatalyzed.


Gel Varnish - 85108 Pt Gel VarnishPrinting Ink and Overprint Varnish Formulations, 2nd Edition, Second Edition (Paint & Coatings)

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