Uneven coatings on wood cause warping

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Material Information

Title:
Uneven coatings on wood cause warping
Series Title:
Technical note ;
Physical Description:
1 p. : ; 21 cm.
Language:
English
Creator:
Forest Products Laboratory (U.S.)
Publisher:
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory
Place of Publication:
Madison, Wis
Publication Date:
Edition:
Rev. Dec. 1952.

Subjects

Subjects / Keywords:
Wood finishing   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Additional Physical Form:
Also available on the World Wide Web.
General Note:
Caption title.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029720281
oclc - 60887174
System ID:
AA00024998:00001

Full Text
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T E C H N ICAL NOTE NUMBER D-12
UNITED STATES DEPARTMENT OF AGRICULTURE FORESa SERVICE
FOREST PRODUCTS LABORATORY
MADISON 5. WISCONSIN REVISED December 1952



UNEVEN COATINGS ON WOOD CAUSE WARPING


Unequal coatings on opposite surfaces of a wood article cause unequal
rates of change in moisture content and hence unequal shrinkage on the
two sides of the piece. The result is that the wood tends to cup or twist
out of shape.

Coatings of nearly equal moisture resistance should be applied to all
surfaces of wood products if the tendency to warp under changing atmos -
pheric conditions is tobe kept to a minimum. Tests at the Forest Prod-
ucts Laboratory show that no coating applied on wood entirely prevents
it from picking up or giving off moisture and, consequently, from swell-
ing and shrinking under the influence of varying atmospheric conditions.

Clear as well as pigmented coatings, regardless of type or composition,
merelydecrease the rate at whichthe moisture content changes in wood
occur In general, pigmented coatings, such as paint, are somewhat
more effective in retarding moisture changes than clear coatings, such
as varnish or shellac, and within practical limits the more coats applied,
the slower will be the moisture changes.

Inexpensive coatings can often be applied to the backs of furniture or
millwork that will be practically equal in moisture resistance to the
coatings on the exposed surfaces. These coatings for backs can usually
be applied in one or two coats, depending on the moisture resistance
required. (See Technical Note No. 181 for the relative moisture-excluding
effectiveness of some commonly used coatings.)



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