Chipping, Flaking, Scaling, Peeling Varnish

Chipping, Flaking, Scaling, Peeling Varnish

Varnish chip, flake, scale, and peel problems in varnishing.

Craftsman Style

¶ Chipping, Flaking, Scaling, Peeling Varnish. These defects are such as show a separation of one varnish coat from another, or of varnish from coats of paint or other color ground. These terms are used to describe different degrees of the same defect,thus, chipping means that the varnish film is coming off in small pieces; flaking means that the varnish film is coming off in larger pieces; peeling1 and scaling refer to still larger pieces of varnish coming off.

¶ These failures often follow cracking and are due sometimes to the same causes. The most common cause is the spreading of a hard, inelastic varnish over an elastic one, lack of uniformity of elasticity in the various coats of the finish. It all comes back to the principle which has no exceptions in varnishing, that from the surfacer to the finishing coats the elasticity of each coat should be increased progressively. And it takes a good finisher to know how to do this. The truth, of the principle, however, is easy to prove by simply reversing the method, by placing the long-oil elastic varnish on first and the short-oil, hard-drying varnish on top as a finishing coat. You can wager anything on the result as being chipping, flaking, scaling, cracking, etc. The only way to work strictly in accordance with the correct principle is to study the varnish you are using. Learn just what it is and what to expect from it. The manufacturer will be glad to advise you on these technical points. Various brands of varnish, even those sold under the same general names such as spar, cabinet, coach, etc., vary considerably in elasticity.

¶ A common cause of flaking is the use of japan color or oil ground color which contains too much binder under varnish. When a greasy surface is varnished without thoroughly cleaning off every trace of grease you may expect one of these difficulties. And when old varnish has been stripped off with liquid remover containing wax, the surface must be thoroughly washed with benzole, alcohol or turpentine to remove the wax film, if you would avoid flaking of the new varnish. And when lye, potash or caustic soda removers are used they are likely to leave some alkali on the surface. If not removed by washing well with dean water the varnish is very likely to flake off. The flaking, scaling, etc., of varnish in some cases is the result of using cheap liquid fillers and not wiping them off clean from the surface. They prevent the varnish coats from gaining a good anchorage on the wood fibre.

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