TECHNICAL STUDIES IN THE FIELD OF THE FINE AI\. TS

Published for the Fogg Art Museum, Harvard University

EDITORIAL BOARD

Chairman of tlze- Advisory Committee: EDWARD W. FoRBES Managing Editor: GEORGE L. STOUT Business Managen WM~ W. BuFFUM

Assi.rtm~~ ;Editot"s: ALAN BuRROUGHS and RuTHERFORD J. GETTE.NS

· ·~ Advisory Committee

\V. G. CoNSTABLE, Courtauld Institute, University of Londort C. T. CuRRELL.Y, Royal Ontario Museum AI.EXANDER EIBNER, Research Institut.e for the Technique of Painting, Technical

High School, Munich PAUL GANZ, University of Basel · A. P. LAURIE, Royal Academy of Arts, London DENMAN W. Ross, Museum of Fine Arts, Boston, and Harvard University ALEXANDER ScoTT, Research Laboratory, British ~useum, London DANIEL V. THOMPSON, JR., Research Fellow of the American Council of Learned

Societies · · '• HENRI VERNE, National Museums of France and School of the Louvre -..:

M~mbers of the Advisory Committee gi':'e ~~luable. aid but are not responsible for the conduct of fECHNICAL STUDIES. Office of Pubhcatlon, Prmce and Lemon Sts., Lancaster, Pa. The Editors should be addressed at the Fogg Art Museum, Harvard University, Cambridge, Mass.; the Business Manager at Prince and Lemon Sts., Lancaster, Pa., or 6 54 Madison Ave., New York

Volume II January, 1934 Number 3

1CONTENTS

Something about Pastel Technic and its Perman.ence WALTER BECK I 19

Notes on rthe l\1edium of Flemish Painters ...... A. P. LAURIE 124 Notes on the Experi1nental Studies Made for the Prevention of

Mold Growth on Mural Paintings ........ ARAM H. HATCH 129 Early Restorations of Mediaeval Enamels ·

MARVIN CHAUNCEY Ross 139 A Chemical Investigation of an Alleged Ancient Greek Bronze

Statuette.· ... o .... 0 ••••••••••••••• ,. o. 0 EARLE R. CALEY 144 Notes

Dammat as a Picture Varnish ..... , ...... " .... MAXIMILIAN TocH 149 Ultra-Violet Rays as Aids to Restorers ........ R. ARcAmus LvoN t 53 Trisodium Phosphate Solutions Attack Marble ... ARTHUR H. KoPP 158

Book Reviews ............. · ... .. 0 ••••••••••••••••••• 0 ••••• 159 Abstracts, .................... . . . .... .. . . ..... : . . . . . . . . . . 160

Application for entry as second-class matter at Lancaster, Pa., post office, pending. Copyright, 1934, Fogg Art Museum .. Made in United States of America.

Issued quarterly $4.00 a year $1.25 a copy : Canada, $4.'15 a year Foreign, $4.50 ~ year

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ULTRA-VIOLET RAYS AS AIDS TO RESTORERS

It is not 1ny intention to delve into the technical side of the ultra­violet rays, but rather to show the practical use of them to the restorer; under certain conditions they are efficacious as indicators of the _ amount of previous restoration one n1ay encounter on the painting under examination. The use of the ultra-violet _rays is many times re­

stricted, however, by a too heavy layer of varnish. The fluorescence of the varnish in these cases is so active that one can not see the true condition of the paint film. It is to be admitted that the trained eye

can in most cases detect former restorations, but the eye does not keep a permanent record of what it sees. The photographic plate does make a record of the greatest value for the trained or for the inexperienced

workers in this field. If surface conditions permit of obtaining such a

record, it ~ill, moreover, help to show an owneror ~urator the actual state of the painting at. that time. Ultra-violet rays, Roe_ntgen rays, and chemical analyses are aids which no restor~r can afford to thrust lightly aside. The Roentgen rays are useful in\ the determination of authorship and as"indicators of the extent of damages under the re­painted areas, but they/ do not always give acclirate indications of the

extent of the repa~nt. Many times the glazes, which hide the original paint, have not enough.opacity to record on the sensitive film used in

making the radiographs. It is thus to be seen that these scientific aids

are not infallible, ~hd can only be successfully used .in conjunction with the trained eye.

Color filters, such as are used in the four-color reproduction proc­ess, are of great value in obtaining a better record of the Jluorescence

produ~ed i~ paintings by ultra-violet light. The following description and illustrations will show the value of the color filter for photography

under the ultra-violet rays, as well as for· exposures made with in­candescent light. Panchromatk plates were used with one exception.

A Corex (\., red-purple filter was used on the q~artz lamp.

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FIGURE I. A portrait of a pope attributed to Girolamo Genga (Fogg Art Museum, No. 19J2.62). .

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154 'liECJ?NICAI .. STUDIES

The painting which is shown in the illustrations is attri but eel to Girolamo Genga (1476-ISSI), U1nbrian School, and is part of the

Fogg Museum collection (No. I9J'2.62). The halftone reproduction

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FIGURE '2. Fluorescence in a detail of the Genga portrait, photographed on a par speed plate.

(Figure 1) is from a photograph ofthe painting under incandescent

light before any cleaning had been undertaken_. The retouchings are

so skillfully done that they are hardly visible to the eye, and the

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NoTES ISS

_values are so closely 1natched that even the sensitive plate of the camera does not record them-a deceptive type of restoration which is preferred by many collectors.

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FIGURE 3· The same area ·as that shown in Figure 2, and also under ultra-violet light, but photographed with a red :filter on the camera, and with a panchromatic :film.

When the painting was placed under the ultra-violet rays, the res­torations were plainly seen as they had taken on a deep, neutralized; blue-violet tone. The original paint film retained its local color ·to a

I 56 'fECHNICAL STUDIES

great degree, except for a slight fluorescence due to the thin filn1 of surface varnish 'which he~:d been extended over the whole painting. The dark tone of the fluorescence seemed to indicate that no color

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FIGURE 4• The lower half of the Genga portrait photographed like the detail in Figure 3·

filter would be needed and accordingly an exposure was made on a panchromatic film with practically no result as far as recording the definite demarcation of the restqrations. A par speed plate wa~ next used in order to check the effect of the fluorescence upon this type qf plate which is practically color-blind.

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NoTES 157

Figure 2 will show the result obtained; the arrow points to light areas which have reversed their tonal value. Under the ultra-violet rays they appeared a dark blue-violet,· although not so mqch neutral­

ized as n1ost of the other restorations. This reversal clearly indicated that by using the red color filter the blue tones would be recorded dark on the panchron1atic film. Figure 3 shows thi~ same area photographed under the ultra-violet rays with the red filter . before the lens. The dark tones of the fluorescence are now recorded· in their proper tonal value as seen by the eye wl~ile the painting is exposed to the ultra­violet ra_ys. The reversal of the light spots indicated by the arrow in Figure 2 is to be noticed. Figure 4 shows the lower half of the painting and is a vivid exampleof fluorescence excited by the ultra-violet rays.

Perha,ps a word here as to exposures inay help some worker in making this type of record. First, he must be sure to sharply focus the image with. the diaphragm wide open, and then~ to stop it down to not

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more thanf I r, for the more open the diaphragm, the more contrast to the exposure. A w·ell stopped-down djaph~an~ wili give detail in the

. lights as w~ll as the shadows but the. resultingnegative will lack the contrast which is obtained by the first type o(exposure. Timing will have to b~;governea by the amount of light whlch the diaphragm lets through, no matter what type of light is used. A- contrasty developer will also be found: to be of great aid in this 1 work because it will increase the contrast in the film and if rightly used will not plug the highlights t.oo muth. A little experience is all tJ\

1at is needed to obtain

the desired results. R .. i\RCADIUS ·LYoN

FOGG ART MUSEUM, HARVARD UNIVERSITY

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