Varnish, commonly known as varnish, is a commonly used transparent paint that does not contain pigments. Varnish is different from cooked oil, because resin, solvent and drier are added to polymerized oil, so its performance is much better than cooked oil.
Varnishes can be divided into short-oil, long-oil and medium-oil varnishes according to the weight ratio of resin to oil. The ratio of resin to oil is about 1:1, which is called short oil varnish. It dries quickly, and the paint film is hard and bright, but its weather resistance is poor, so it is only suitable for painting indoor woodware; when the ratio of resin to oil is greater than 1:3, It is called long-oil varnish. Its paint film is slow to dry, full of elasticity, and has good anti-atmospheric effect, but the paint film is soft and not resistant to friction. It is only suitable for painting outdoor woodware; if the content of resin and oil is within Between short oil and long oil, it is called medium oil varnish, its properties are also between long oil and short oil, and it can be applied to both indoor and outdoor woodware.
Other properties of the varnish are determined by the type and nature of the resin used.
For example, the calcium ester varnish made of lime rosin has a hard film, good gloss and fast drying, but poor water resistance. The ester varnish made of glycerin rosin has a water resistant film at the beginning of the film, but the drying property is not good and the gloss is also poor. It is not durable; the dynamic aldehyde varnish made of modified phenolic resin has low viscosity, fast drying of the paint film, good gloss, good water resistance and weather resistance of the paint film, but the paint film is easy to yellow; use alkyd resin The alkyd varnish produced has light color, is not easy to yellow, has good gloss retention, and has strong wear resistance and weather resistance; but it is not as convenient to brush as phenolic varnish, and its leveling property is poor. It is not suitable to brush again after a few minutes of brushing. Therefore, there should be certain operating skills.
The improved gold paint made of modified aldehyde resin, tung oil, asphalt and oil-soluble dyes is also called red palm phenolic transparent paint. It dries quickly, has good luster, and has a reddish brown color. It can replace wide paint and is used for Painting interior wooden furniture. The disadvantage is that the paint film sometimes has stickiness phenomenon, and it is easy to fade when exposed to direct sunlight for a long time; the decal varnish made of maleic anhydride rosin sidang and glycerin rosin cool has fast drying and good adhesion, and is suitable for pasting labels on light industrial products and patterns.
The nitro varnish synthesized with nitrocellulose and alkyd resin has the biggest advantages of fast drying, bright and hard coating, can be polished and polished, resistant to lake humidity, and has good mechanical strength, so it is used for the coating of high-grade wooden crystals. Pack. Its disadvantages are low solid content, troublesome construction procedures and high cost. Therefore, acrylic modified nitro varnishes have been used at present, which not only maintains the advantages of self-drying and quick-drying nitro varnishes, but also overcomes the shortcomings of thin coating film and poor protective performance.
