Robert L. Feller

DARKENING OF PAPER FOLLOWING EXPOSURE TO VISIBLE AND NEAR-ULTRAVIOLET RADIATION

AbstractIn a series of experiments using three different sources of visible and ultraviolet radiation, post-irradiation darkening at room temperature of water-leaf papers made from various pulps is shown to be chiefly influenced by the content of lignin and by the pH of the test sheets.

Changes in Solubility and Removability of Varnish Resins With Age

AbstractA series of mixtures based on cyc1ohexane, toluene and acetone have been employed to investigate the solvent power needed to remove various varnish resins in the course of photochemical deterioration. Under ordinary conditions of exposure, dammar and mastic resins tend to reach a maximum degree of oxidation at which time mixtures of no greater solvent power than 60/40 v/v toluene/acetone are needed to remove the aged coatings. Polycyc1ohexanone polymers tend to lose their solubility more slowly than the two natural resins but may in time require solvents of higher solvent power to remove them. In contrast, the two highly stable polymers, polyviny1acetate and Acryloid ®B-72 essentially maintain their solubility and removability in the solvents in which they were originally soluble, mixtures of lower solvent power than toluene.An investigation of the actual percentage of the resins dissolved by the various solvent mixtures indicates that, in the case of po1yviny1acetate and Acryloid ®B-72, solubilit...

Determination of the Specific Rate Constant for the Loss of a Yellow Intermediate During the Fading of Alizarin Lake

AbstractIn the course of photochemically-induced fading, alizarin lake mixed with a photochemically-inert titanium white in a poly(vinylacetate) vehicle apparently passes through a yellow intermediate stage. A simple graphical method is described which permitted calculation of the specific rate constant for the first-order rate of fading of the yellow intermediate.

Aspects of Chemical Research in Conservation: The Deterioration Process

AbstractBefore safe and effective practices in conservation care and treatment can be introduced, the chemist is called upon to address numerous aspects of the proposed innovations. The effort to p...

A Note on the Exposure of Dammar and Mastic Varnishes to Fluorescent Lamps

The oxidation of these traditional varnishes has been noted by Mills and Werner (1), Thomson (2), and the author (3). In studying the effect of light on them, one would wish to know just what effects are easily detected and how much exposure is necessary to bring them about. A gain in weight and a loss of solubility are readily observed. The results of preliminary experiments are herewith reported.

Studies of the Effect of Light on Protective Coatings Using Aluminum Foil as a Support: Determination of Ratio of Chain Breaking to Cross-Linking

A convenient demonstration of this procedure can be arranged by using some of the new feltor nylon-tipped writing tools. Some of these have permanent color inks; some, water-soluble inks (e.g., Esterbrook Felt-Riter pens). If two such pens, one with permanent ink and one with water-soluble ink, are both used to mark a small piece of paper or cloth, the water mark can be removed completely without touching the permanent color mark. The paper or cloth is hung in a sealed glass jar with a few milliliters of water in the bottom. In a few weeks at room temperature, or less time (a few days) at elevated temperatures (say 150?F on a hot plate), the water-soluble ink will be completely removed and the permanent color markings will be unchanged. s or cloth may be su ported on another sheet of paper. oce s may be a c lerated by heating the container l although one must first be certain that n compoi soluble at r om temperature becomes soluble at an e te perature. Before risking any museum object to this treatment one must be very sure of the relative solubilities of all of the various components of the object. The usual method of removing soluble matter on the surface of objects by employing cotton swabs wetted with the solvent is a safer procedure in the sense that exposure to the solvent is very short and trials can be made at the edges. Even if this traditional procedure is to be used, the solubility test described above should be employed because it requires less material and because it gives the operator more confidence that he has found the proper solvent.

The Use of an Electrically-Conducting Glass Panel as a Heating Surface

An advertisement seen some time ago, describing the use of electrically-conducting glass to eliminate ice from windows in airplanes, prompted the National Gallery of Art Research Project at Mellon Institute to consider the application of such panels as a heating surface in the conservation laboratory. With the current interest in heated metal tables and composition-rubber blankets, the thought immediately occurred that the ability to see through the heating surface and to watch the work as it was dried and pressed into shape would be of an advantage in certain problems.