Initial heating of the phenol and formaldehyde (in the presence of an acid or base to get the reaction going) produced a shellac-like liquid good for coating surfaces like a varnish.
开始加热，酚和甲醛(需有酸或碱促使其反应进行)便产生了像紫胶样的液体，能像清漆一样涂于物体表面。
2
Base on the knots, application of shellac varnish resin parts closed, oily putty inlaying nailhole place application.