1136
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 22, No. 10
Resistance to Tackiness of Certain Paint, Varnish, and Lacquer Coatings on Interior o f Cedar-Lined Receptacles’ Frank Rabak BUREAU OF
P L A N T INDUSTRY.
U. s. DEPARTMENT OF AGRICULTURE, WASHINGTON, D. C.
ANUFACTURERS of metal cedar-lined safes and cedar chests used for the storage of clothing and furs for protection against moth damage are confronted with the serious objection of the trade to the stickiness or tackiness of the painted or varnished metal surfaces inside these receptacles, with possible resultant damage to the material stored in them. Investigation of the problem disclosed that the inside surfaces of the doors, hinges, locks, and jambs of the safes or chests lined with red cedar are coated at the time of manufacture with oil-base colors or varnishes of standard usage. These coated surfaces soon soften and become sticky, often with considerable resultant damage and expense to the articles stored in the receptacles. The cedar lining, which consists largely of the heartwood of red cedar, Juniperus uirginiana, was suspected of being the cause of the trouble, which was explained by the fact that the vapors of red cedar, which are concentrated within the interior and which consist of the volatile oil of cedar, act as a solvent for the oils in the coatings used on the inside metal surfaces, thus softening the same to a point of extreme stickiness or tackiness. It is evident that in order to correct the trouble certain types of protective coatings must be used that will resist softening in a concentrated atmosphere of cedar vapors. A small replica of a cedar-lined safe was constructed for use in testing numerous steel panels to be coated with various types of coatings, such as paints, varnishes, and lacquers, and then placed in the safe for observation. It was hoped that some inexpensive yet effective coating would thus be revealed which could be used instead of the usual paint or varnish to overcome the objectionable tackiness with its resultant damage to materials placed in the safe. A total of seventeen materials, representing several types of coatings, mostly products purchased in the open market, were chosen for the tests. Small steel panels were coated with the materials and when thoroughly dry were placed in the safe. The tests were conducted over a period of 18 months, examination of the panels being made at three intervals of approximately 2, 6, and 18 months. The accompanying table shows the results of the tests. Of the four general types of coatings-paints, varnishes, lacquers, and bronzes-those containing untreated drying oils in considerable quantities were found to be least effective, while all coatings free from drying oils as color vehicles or containing only very small quantities of drying oils were most effective. Flat paints, such as undercoat white, interior wall finish, and flat wall paint, all of which contain a minimum quantity of drying oils, were found very effective, being distinctly non-tacky after 18 months. These apparently afford a cheap yet effective coating for the interior metal surfaces of the safes. Enamels and varnishes, as well as asphaltum, it will be observed, were ineffective. The tackiness of these panels was attributed to the linseed oil used in the preparation of the products. Radiator bronze with a non-oil vehicle was found to be very effective in preventing the objectionable stickiness. The lacquers used were uniformly effective, with one exception, a panel
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Received July 9, 1930.
coated with black lacquer, the history of which was not known. Brushing or spraying lacquers of any desired color can a p parently be used with safety and effectiveness on the interior metal surfaces of the safes, combining ease of application, quick drying, and smooth attractive appearance. Flat paints, like those previously mentioned, are perhaps equally as effective and somewhat less expensive than lacquers, but produce a less attractive appearance and require more time to dry to a hard film. It is apparent from the above tests that the cedar vapors emanating from the cedar lining in the receptacles act as a slow solvent of the oil vehicle of certain coatings, softening the film to the point of extreme stickiness, much as would red cedar oil itself if i t were brushed on the coated surface. This is proved by the fact that flat paints made with turpentine, as the principal vehicle for carrying the pigment, and containing practically no oil, are not softened by the vapors. Likewise, radiator bronze, and lacquers with special vehicles or thinners, are unaffected because of the absence of appreciable quantities of oils in the f i l m of these products with their consequent insolubility in the cedar vapors. Tests on S t e e l Panels Coated w i t h Paints Varnishes, Lacquers, and Bronze Placed in C e d a r d i n e d S a f e
DESCRIPTION OF
COATINO
SECOND EXAMI- THIRD EXAMI-
FIRST BXAMI-
NATION NATION (JULY 29,1928) (Nov. 29,1928) PLACED I N CHEST MAY 21., 1928 - -
Gray lacquer
Non-tacky, no change Tacky Non-tacky. no change Brown enamel Tncky Auto color varnish Slightly tacky Gold radiator bronze Non-tackv. no change- ’ Clear lacquer Non-tacky, no change Coach varnish Very slightly tacky Asphaltum Non.tacky, no change Black lacquer Silver gray lacquer
NATION
(Nov. 29,1929)
Non-tacky, no change Very tacky Non-tacky, no change Very tacky Very tacky Non-tack\.. no change-’ Non tacky, nd change Slightly tacky
Non-tacky, no chnnge Tacky Non-tacky. no changeVery tacky Very tackv Non.tacky. no change Non-tacky, no change Tacky
Tacky
Very tacky
~
PLACED I N CHEST J U N E 16, l 9 l s
Interior wall finish (flat) Spar varnish
Non.tacky, no change Non-tacky. no change China wood oil paint Slightly tacky (white lead) Flat wall paint Non-tacky, no change Undercoat white Non-tacky, no paint (flat) change Hempseed oil paint Slightly tacky (lead carbonate) Tacky Safflower seed oil paint (lead carbonate) Linseed oil paint Non-tacky, no (white lead) change
N o n tacky, no
change Non-tacky, no change Very tacky
Non-tacky, no change Non-tacky, no change Very tacky
Non-tacky, no change Non-tacky. no change Very tacky
Non-tacky, no change Non-tacky, no change Very tacky
Very tacky
Very tacky
Slightly tacky
Tacky
It is unlikely that the stickiness or tackiness is due to a n exudation from the paint films or that condensation of cedar. vapors, followed by resinification, takes place on the metal surfaces, which has been claimed by some, since neither the flat painted surfaces nor the lacquered or bronzed surfaces exhibit the slightest sign of tackiness due to the condensation and residication of cedar-oil vapors on these surfaces. The Investigation of Atmospheric Pollution. Report on Observations in the Year Ended 31st March, 1928. Fourteenth Report. Department ot Scientific and Industrial Research. 67 pp. H. M. Stationery O f i c e , London. Price, 3 s. 6 d.
