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Finishing                                                           Finishing materials                       All About Oi...
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Finishing materials


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Finishing materials

  1. 1. Finishing Finishing materials All About Oil Based VarnishFor many amateur woodworkers or hobbyists who either cannot afford sprayequipment or do not have enough space in their shop to set up a spray booth tosafely spray finishes like lacquers, brushing on an oil based varnish is one of thebest choices for a topcoat finish. Oil based varnish does not dry very quickly,therefore it will take longer to complete a finishing project using varnish asopposed to lacquer, water based or other faster drying finishes. However, if youare an amateur or home woodworker, not a pro who has to worry about meetinga deadline, time should not be top priority, quality should. Varnish has very goodresistance against abrasion, wear, heat, solvents and water vapor. Other than itsslow drying time, which can also cause problems with dust getting trapped in thefinish before it dries, the only other disadvantage to oil based varnish is that ittends to yellow over time. The dust problem can be taken care of by setting up adust free finishing area in your shop and sealing it off with heavy plastic to reducethe amount of dust and sawdust in that area. The problem of yellowing cannot behandled as easily. First, most oil based varnishes are amber (yellowish) in colorto begin with. This is because the oils used to make the varnish are amber.Therefore, oil based varnishes tend to somewhat change the color of the raw orstained wood when they are applied. It is not a considerable change, and unlessapplied over a very light colored or white stain, it is satisfactory. In fact, ambervarnishes actually give darker woods like walnut and mahogany a warmerappearance. Non-amber or what are called water white finishes like somelacquers and water based finishes can leave a cold look on darker coloredwoods. However, if needed, there are a few water white varnishes available. Oneis called water white restoration varnish manufactured by H. Behlen & Bro.Nothing can really be done about yellowing of varnish over time and if you thinkabout it, all film finishes break down in one way or another over time and have tobe removed and replaced with a new finish. Tung oil yellows less over time thanother oils, therefore a varnish that contains tung oil will have a tendency to yellowless over time.Oil based varnish is manufactured by cooking certain oils that can cure withresins. Once this blend of cooked oil and resin is complete, solvents are added tomake it thin enough to apply and metallic dryers are added to help speed up thecuring time. Initially, linseed and tung oil were used by manufactures for thecuring oils and natural resins like pine and gum resins were used along withsolvents like gum turpentine and mineral spirits (to thin it out) and lead used forthe drier. These ingredients were not only used to make varnish, but also paint.With the exception of lead, you can sometimes still find some of theseingredients in todays oil based varnishes, but modern varnishes usually usesynthetic resins which are superior in strength and longevity and curing oils thatare less expensive to use in the manufacturing process along with a blend ofsolvents and metallic dryers like cobalt and zinc that do not cause healthproblems such as lead Wisdom Management Services (M) Sdn. Bhd. 1