The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California

Coloring Finishing And Painting Wood

The chemical theory of the use of driers as oxygen carriers or catalysts does not seem to take all the reactions into account, and it is evident that part of the phenomena are to some extent physical. There seems to be a greater activity or reaction in a drying film at its surface than elsewhere, and it is probable that a portion of the drier moves to the surface and forms a greater concentration of drying forces just at the place of contact of the air with the film.

The cobalt driers which are sometimes found on the market or which are made in factories are cobalt acetate, cobaltous oxide, cobalt resinate, and cobalt linoleate. Until quite recently cobalt linoleate was the only cobalt drier commonly used, but now combinations of cobalt with some of the other organic-oil acids are considered excellent driers.

The lead salts and compounds used as driers are: litharge, which is lead oxide (PbO); red lead, which is called the sesquioxide ; lead acetate, , also called white sugar of lead; lead borate, ; lead resinate, ; lead oleate, ; and lead linoleate, .

The various manganese driers that can be used are: manganese dioxide (MnO2); manganese borate in dry form (MnB2O4); managanese sulphate (MnSO4 + 4H2O); and occasionally manganese chloride (MnC2 + 4H2O). Besides these, the linoleates, resinates, and tungates of nianaganese are also used as driers. The manganese driers discolor varnishes but little, being much superior to the lead driers in this respect. The lightest in color of all of the manganese driers are the sulphate and the borate; consequently, these salts are often selected as driers for very pale varnishes.

Umber, a ferric oxide containing manganese oxide and clay, receives its drying properties from the manganese content mainly; therefore, it should be considered as a manganese drier rather than an iron drier. Manganese driers are superior to lead driers in resistance to moisture; and, partly for this reason, they are used in connection with lead driers in water-proof varnishes.

For use in paint mixtures manufacturers often select an oleate of lead and manganese which contains about two parts of lead to five parts of manganese. In fact, oleates or resinates made from the two metals just named are commonly used in driers. Driers containing both metals in compounds are often preferred to those made from one of the metals alone, because manganese driers are said to expand in drying while lead driers react differently and are thought to contract.

Concentrated driers may contain as much as twelve per cent of metallic drying-salts when compounded in liquid form, while weaker driers sometimes are manufactured with only two per cent.

Painters' japans are liquid mixtures of driers, and usually contain a varnish-gum or resin in addition to the other ingredients ordinarily found in driers. The gums used in japan-driers are among the cheapest of the varnishresins such as rosin especially, and sometimes shellac, and kauri.