COOS HEAD fUTIBER E P1YWOOD CO. A R G o

From

Our

P.Cl. Box 3O5 - Wilmingron, Cqlif. QUALITY & SER,VICE

Mills qt Coos Boy ond Wqrehouse ond Yqrd ot Berth 135, Wilmington

,Wtt PRNilNG OF WOOD SIDING

By John Reno, Utilization Director, The Pacific Lumber Company

: Mill priming of siding is receiving much publicity and some of it is misleading.

', .In the first place, the term "mill priming" is being given to mill treatments with water-repellent preservatives. This is not correct since these treatments do not remove the need for priming with paint.

The most widely used mill treatment is dipping into a clear water-repellent preservative solution like Nelsonite 30P5, Penta WR, Woodlife or'Woodtox, or into Lifeprime White which is a liquid somewhat like Woodlife to which a small amount of white pigment has been added. Vacuum impregnation with these products has.also been done.

These types of mill treatment protect the siding against paint blistering and staining caused by rain water which gets back of the siding. Almost equal protection against rain water can be had by generously applying these and similar products by brush to the backs and ends of siding just pefore putting the siding on the house.

- As mentioned previously, these types of treatment do not take the place of a prime coat of paint or reduce the number of coats of paint needed to do a good paint job. The United States Forest Products Laboratorv still recommends three coats of paint whether or not th,! siding is treated with a water-repellent preservative. The treatment does not add to the life of the paint job, except that it protects against rain-caused paint blistering.

The ORIGINAI Crystol Cleqr Plostic Spor, a nnish especiqtly recommended for qtl types of wood. Accenls, beoutifies ond retqins the originql color. Suiroble for interior or exterior use.

Coll or wrile us for triol order. We guqro,nfee you won'i be disoppoinled.

Security Patnt

MANUFACTUR,ING CO.

162l No,Indiqnq Slreet, Los Argeles 63

Tefephone: ANgelus l-0359

The next question is: Does paint 'blistering due to rain water occur often enough to warrant the extra cost of mill treating with a water-repellent preservative ? Or, is the promotional value of being able to say that siding is treated against rain-caused paint blistering great enough to cause one to pay more for mill-treated siding?

Treating with a water-repellent preservative offers very little protection against paint blistering and staining caused by the movement of water vapor through the walls from high humidity inside a house. The only real orotection against this trouble is the use of a vapor barrier on the warm side of the exterior walls.

Mill priming with a regular paint is very risky. This is so because it is necessarv that the second and third coats of paint be of a type that will work satisfactorily with the prime coat. As a matter of fact, the only real safe way is to use a priming paint and a finishing paint made by the same manufacturer. Since there are five popular types of white house paints and scores of paint manufacturers, you can see that mill priming with a regular paint presents a real danger.

So-called back priming on the job with regular paint as practiced today is a waste of money. However, back and