RESTORING THE PANAMA MURAL PAINTINGS ALBERTB. NEWMAN, COOPERUNION, NEW YORKCITY
During the construction of the Panzma Canal, the late General George W. Goethals, then Colonel and in charge of the project, commissioned Mr. W. B. Van Ingen, the mural painter, to execute a set of mural paintings telling the story of the construction. These paintings were to be placed on the curved side walls of the rotunda in the Government Administration Building, Balboa Heights, Canal Zone. Before executing the paintings in New York, Mr. Van Ingen spent about six months a t the canal site, studying the construction operations, making sketches and receiving criticisms and suggestions from Colonel Goethals. Finally the Colonel gave the word that the sketches were satisfying to him from the standpoint both of the scope of construction operations portrayed and of the correctness of detail, and the artist was authorized to proceed with the canvasses. He then produced a set of pictures achieving the rare combination of high artistic merit and engineering accuracy. If these pictures should he destroyed, they could not well be replaced, owing to the fact that much of the detail shown is now under water and the fact that the events shown have passed into history. Late in 1928, the Governor of the Canal Zone advised Mr. Van Ingen that the paintings had been attacked by the mold growths which are so prevalent in tropical regions, and requested him t o visit the Zone to discuss what measures might be taken to resto~ethe paintings to their original condition and t o protect them against future attacks. Before sailing from New York, Mr. Van Ingen discussed the matt& with the writer, and a number of tentative suggestions were made to assist him in discussing the matter more intelligently upon his arrival. The first fact to be considered was that the paintings were permanently attached to the walls. That eliminated consideration of any procedure which would involve fumigating with vapors toxic to the mold. The first off-hand suggestion was to apply a fungicidal wash, retouch any affected paint areas, and then to coat the clean surface with paraffin to which a small percentage of cresol had been added. It was realized that the use of cresol was open to objection on account of odor and low melting point, and that some other member of the phenol family having more suitable properties might be found. There was insufficient time to make a study of these matters. Mr. Van Ingen visited the Canal Zone during December and returned with cultures of the mold and with instructions to get the details of a procedure worked out with a view to negotiating a contract with the Government covering the restoration of the paintings. In a letter to Mr. Van Ingen, Dr. Lewis T.Bates, Chief of the Board of Health Laboratory of the Panama Canal, quotes from his laboratory records as follows: 873
874
JOURNAL OF CHEMICAL EDUCATION
.
APRIL,1930
Dec. 20. 1928 Mold .from Mural Paintings in Rotunda of Administration Building, Bnlboa ~leights,C. Z. Specimens removed under the direction and in the presence of Mr. W. B. Van Ingen, the artist who originally painted the pictures. These paintings have many areas showing considerable growth of mildew. I n most places the individual growths of the mildew are about the size of the head of a pin. They are white in color. They cannot he brushed off, they cannot be rubbed off, and they cannat be removed by gentle scraping. The only way t o remove them seems t o be by scraping with hard pressure taking off considerable paint a t the same time and by digging them out with the point of the scalpel. In this latter manner enough mold was removed t o inoculate four tubes of Sahoumud's media (two from the east wall and two from the west wall), and four plain agar slants (two from the east wall and two from the west wall). Two of the tubes of Sabouraud's media and two of the plain agar were delivered t o Mr. Van Ingen t o take to the United States. Two small tubes containing a small amount of the scrapings from each side were also delivered t o Mr. Van Ingen. I n a cover slip preparation of the mold examined under the microscope many ascospores could be seen.
The mold cultures were submitted by the artist to Dr. Charles Thom, Principal Mycologist of the Bureau of Chemistry and Soils, U. S. Department of Agriculture, a t Washington, who wrote the following: Several organisms were present in the cultures but mast of them were regarded as non-significant, merely incidentally present. One of these cultures, however, produced extensive growth covering the entire culture medium in our petri dishes, giving an extensive mycelium in the substratum and upon the surface of the substratum, hyphae colored brown or greenish brown. Thus f?r I have discovered no spores which would permit of botanical identification. The general group to which it would be assigned as a hyphomycete contains a series of species with the* brown heavy walls capable of growing in situations alternately wet and dry, capable of drying up without perishing and resuming activity whenever the moisture conditions become favorable. This organism suggests hy its habits and appearance, that i t belongs among this series of species, same of which one or two of my colleagues have already studied in connection with painted surfaces. Elimination of such or~anismsmay be reached by . (1) . . permanent dming . .of the substratum; (2) the penetration of the substratum by some substance whieh will not permit access t o the nutrients on the part of the mold; (3) the soaking or penetration of the substratum with some disinfectant or antiseptic which will remain there and become soluble in minute quantities every time there is access of moisture, thus tend t o prevent mold growth. Without first-hand experience with a paint problem in the tropics we are not in a position to settle which is the best line of procedure. ~
The writer thought that there must be many sources of information about work of this kind and, inasmuch as the nature of the problem was foreign to anything in his previous experience, he encouraged the artist to get what information he could from local museums of art and from publications in the art field. He obtained little information from persons whom he consulted in New York and the publications were of a sem-scientific nature requiring interpretation for one without chemical training. Owing
VOL. 7, No. 4
THE CHEMISTRY STUDENT
875
to these difficulties and on account of the connection of both the writer and the artist with the Cooper Union for the Advancement of Science and Art, the writer decided, somewhat reluctantly, to take the responsibility of guiding Mr. Van Ingen in establishing a procedure. It was definitely understood that the final procedure must be passed upon by the Governor, who had the advice of the scientists on the Canal Zone, before the actual work on the paintings should proceed. The canvasses were bought "unprepared" and the artist cdvered them on both sides with Valspar. Ordinary tubes of artists' oil colors were used, the pigments being zinc white and permanent colors. Four of the canvasses were approximately 10 X 20 feet each and the fifth was a frieze to be placed below the four paintings. The frieze was delivered in Panama in the spring of 1914, but the building had not been completed, and the frieze was rolled on a drum 3 feet in diameter and stored in a completed part of the building. The other canvasses were delivered and placed in the spring of 1915 without going into storage. I n 1928, the greatest mold growth was on the frieze. The bare walls were surfaced with Keene's Cement. The cement surface was given two coats of shellac, after which the canvasses were attached by means of a thick layer of white lead and dammar varnish. After placing, the face of the canvasses was coated with a solution of beeswax in turpentine, leaving a film of beeswax for the protective coating. In working out a procedure for the restoration and future protection of the paintings, it was obvious that the following general procedure would have to be followed: Cleaning the surface to remove superficial dirt; removing the beeswax film without damage to the paintings; killing the mold growths by the application of fungicide; removing the dead mold, followed by another fungicide wash to insure an aseptic surface; retouching by the artist, if and where necessary; applying a protective coating containing fungicide. Taking up these items in order, the details follow. It is well known among artists that paintings should he washed with saponin solution in preference to soap solution. This is mentioned by Laurie' and others. For the removal of the beeswax film, it is well known that a satisfactory procedure is to give the surface alternate applications of turpentine and alcohol. The turpentine is the solvent and the alcohol performs a restraining action on the turpentine, minimizing possible damage to the paint film. These methods are also discussed by Laurie.' The killing of the mold growths involved the selection of a fungicide. While considering the choice of a phenolic compound, our attention was "The Painter's Methods and Materials," A. P. Laurie, J. P. Lippincott Company, 1926.
A76
JOURXAL OF CHEMICAL EDUCATION
.
APRIL,1930
called to the work of Dr. Alexander S c ~ t t Director ,~ of Research of the He reported marked success in killing mold growths British Museum. on small paintings and prints by fumigating in a closed chamber with thymol vapor. In a personal letter to Mr. Van Ingen, Dr. Scott stated that, as far as he could trace, there had been no recurrence of mildew or mold on anything they had treated, and that nothing had occurred to weaken their faith in the thymol treatment when thoroughly applied. This statement was made after experience with the fumigating treatment covering about ten yeare. Morris3 carried out a coinprehensive set of mold growth experiments using varying concentrations of a large number of fungicidal substances upon cultures of molds procured from many different countries. Some of the molds were more sensitive to fungicides than others, but he reported that a concentration of 0.05% of thymol completely inhibited the growth of the hardiest mold culture in his collection. His work showed thymol to have a FlGnRE 1.-PHOTOGRAPH SHOWING A SHALL AREA phenol coefficient of 2.6. OF THE FRIEZE BEFORERESTORATION. THE VER- He also pointed out that TICAL CHALKLINEIS SIX INCHES LONGAND IS DIwhile, in general, subVIDED INTO INCHES stances effectiveas germicides are also effective as fungicides, the phenol coefficients of the same substances used for the two purposes may be widely different. This is borne out in the present case by a private communication received by Mr. Herman Yagoda, the writer's assistant in this work, from Dr. Oliver Kamm, of Parke, Davis and Company, in which he states that as a general thing thymol is considered as having a phenol coefficient of 25 to 30, depending
,
"The Cleaning and Restoration of Museum Exhibits," Alexander Scott, Third Report. H. M. Stationery Office, London, 1926. 3. Textile Inst., 18, T99 (1927).
VOL.7, NO.4
THE CHEMISTRI' STUDENT
877
upon the individual worker and the particular method used. In order to get an idea of the vapor concentration used by Scott, several points on the vapor-pressure curve of thymol were determined in our laboratory. The points were used in plotting the vapor-pressure curve, by means of Duhring's Rule,* using the known curve for o-cresol as a standard. This work showed that thymol has a vapor pressure of only about 1 mm. in the temperature ranxe . used by Scott. All of the evidence therefore pointed to the fungicidal effectivenessof thymol in very small concentrations. Even though we did not know the identity of the mold a t Panama, it was thought that we were justified in deducing that a 57& solution of thymol, a concentration 100 times as large as the minimum determined by Morris, would kill any mold. Alcohol was found to be a satisfactory solvent. For this step in the procedure, a 5% solution of thymol in alcohol was finally adopted. It was decided that the dead mold spots could be removed by going over them with alcoholic amFIGURE 2.-THE SAMEAREAOF THE FRIEZESHOWN IN FIGURE 1 AFTERRBSTORATION monia solution. Then, after washing axain with the alcoholic~thymolsolution, the artist could do whatever retouching he thought necessary. Thymol having been selected as the fungicide, it was thought desirable, as an extra precaution, to keep some of this substance permanently in contact with the paintings. A protective coating which would keep out atmospheric moisture, dirt, and mold spores, would also prevent the thymol from vaporizing and escaping. Paraffin seemed to be a suitable material, and, from the artist's standpoint, it possesses the notable property of producing ' "Principles of Cherdi'cal Engineering," Walker, Lewis, and McAdams, McGrawHill Book Company, 2nd edition, 1927.
878
JOURNAL OF CHEMICAL EDUCATION
APRIL. 1930
ROTUNDA DECORATIONS I N THE ADMINISTRATION BUILDING AT BALBOA. MIRA~LORES LOCKS UNDER CONSTRUCTION. A PORTION OR THE CIRCULAR FRIEZE IS VISIBLE . .
a dull, pleasing finish, and of being &sparent and colorless when applied i n thin films. Paraffin also conforms to t8e requirement of removability, being easily soluble in petroleum ether. If paraffin were to be selected, several questions would have to be answered. Should i t be applied in molten condition or in solution in a volatile solvent? If applied in solution, would the evaporation of the solvent leave a homogeneous or a porous film? How much thymol could he added to the paraffin without too much lowering of its melting range? If the solvent method should give'a homogeneous coating, tben that would he the more convenient method, but should the solution be applied with a brush or with a spray gun? What solvent should be chosen and what strength of paraffin-thymol solution should be applied in order to give a coating of proper thickness? All of these questions had to he answered by laboratory experimentation. On looking up paraffin solubilities, petroleum ether seemed to be a satisfactory solvent for experimental purposes. Several glass slides were coated with molten paraffin and others with paraffin solution. The paraffin films were tben examined under the microscope and no difference in homogeneity could be detected. Inssmuch as the films formed by the evaporation of solvent showed no porosity, it was immediately decided that the solvent method should be adopted. Furthermore, the slides coated by the solution
.VOL.7, NO. 4
THE CHEMISTRY STUDENT
LOCKGATESUNDER
879
EAECI'ION
method showed no brush marks, but those coated by the melting method resulted in thicker films and the brush marks were visible. Melting temperature experiments with paraffin contain:'ng various known percentages of thymol were carefully made, and it was found that the melting range of any given sample of paraffin was lowered 0.7"C. by adding 1% of thymol. Over a considerable range, the relationship of added thyrnol to melting range lowering was linear. Owing to the tropical climate, it was thought desirable to use not over 2% of added thymol, giving a lowering of only about 1.4'C. in the softening point of the paraffin. Using petroleum ether as a solvent for paraffin, atomizing experiments were made, but these all resulted in a rough surface, due to the entrainment of air bubbles and the rapid evaporation of the solvent. On the other hand, applying the solution with a brush left a smooth uniform film. Although the work would require coating about 1000 square feet, it was decided that the brush method was the only one that could be considered. Two solvents were considered, petroleum ether and benzene. Solubility determinations showed that, a t room temperature, paraffin was soluble to the extent of about 19% in petroleum ether and of about 12% in benzene. Experiments on vertical surfaces showed that the rapid vaporization of petroleum ether as compared with benzene made the former more easily applied. The benzene solution had a tendency to run down the surface
880
JOURNAL On CHEMICAL EDUCATION
.
A P ~ 1930 ,
I
CUCARACHA SLIDEAND CULEBRA CUT DURING
CONSTRUCTION
DAYS
before the film had an opportunity to form, while the petroleum ether vaporized almost instantly. In the course of the experimentation with petroleum ether, it was found that a s o h i o n which had been allowed to stand for several days gave, when applied to a surface, a sticky film which did not harden immediately, finally turning into a surface rougher than that made from fresh solutions. It was therefore concluded that fresh paraffin solutions should be made up each day. By weighing glass slides and cellophane strips before and after application of paraffin films, it was determined that the film thickness when deposited from an almost saturated solution was about 0.0001 inch. It was obvious that, by using nearly saturated solutions, as many coats as desired could be superimposed upon each other, as the first coat would not be dissolved in the nearly saturated solution used in applying the second coat, etc. The question as to how many coats were desirable was left for future decision after the first coat had been applied. On looking into the question of the different grades of paraffin on the market, i t was decided to specify the refined product having a melting range of 56-5S°C. This material has the highest melting range of the four grades readily available on the market. Following is a summary of the procedure finally recommended. Wash the surface of the paintings with a solution of saponin in water. Remove the beeswax finish by alternate applications of turpentine and alcohol, being
VOL. 7, No. 4
THE CHEMISTRY STUDENT
88 1
careful not to damage the painted surface. Wash the surface with a 5% solution of thymol in alcohol. Remove the mold spots by applying a weak solution of ammonia in alcohol. Rewash the entire surface with the solution of thymol in alcohol. Retouch any damaged paint areas. Brush on a solution of paraffin and thymol in petroleum ether, containing 17-18y0 paraffin and 2% tbymol based on the paraffin. Apply a second coat if it seems desirable. When this procedure was laid before the Governor, a question was raised as to the maximum temperature of the rotunda and the possibility that the paraffin-thymol coating might soften a t this temperature. In order to satisfy every one on this point, a recording thermometer was placed near the paintings and a continuous record taken for a week. Glass slides coated with the paraffin-thymol were suspended near the pictures and kept there during the same period. The mzximum temperature recorded was 90°F. and no softening of the films could be detected. Then the entire procedure was adopted and authority was given for the work to proceed. After the paintings had been cleaned, it became apparent that no retouching was needed. With this exception, the work was camed out strictly in accord with the outlined procedure. An unexpected result was the freshening of the coloring of the paintings. The restoration of the paintings was completely successful. Only time will tell whether or not they have been protected against future mold attack, hut i t is felt that every reasonable precaution has been taken. If a t some future time there should be a recurrence of mold growth, i t would be an easy matter to wash off the paraffin 8lm by the use of petroleum ether or gasoline. Then the mold could be destroyed and removed by the methods outlined above, after which a fresh coating of paraffin could be applied. All of this work could now be handled in a routine manner by skilled labor. Mr. Van Ingen holds a letter from the Governor expressing his satisfaction with the results obtained. The writer desires to express his appreciation of the faithful and capable assistance rendered by Mr. Herman Yagoda, who camed out the experimental work in New York and who assisted Mr. Van Ingen in executing tbe work a t Balboa Heights.
Reform of Nomenclature of Organic Chemistry. The Division of Chemistry and Chemical Technology of the National Research Council is circulating a report of the Commission of the International Union of Pure and Applied Chemistry on the Reform of the Nomenclature of Organic Chemistry and is seeking comments a"d criticisms of the proposed rules. I t is expected that the rules will be further considered at the meeting of the Union at LiPge in 1930. Any criticisms or suggestions should be sent to the chairman of the American committee, Austin M. Patterson, Xenia, Ohio.-Ind. Eng. Chenz., News Ed.
