Survey Methodology for a Collection of Technical Drawings

1 Introduction

Technical drawings constitute an important part of the archival legacy of the world, since they document the planning and the construction of all kinds of buildings, industrial facilities, machinery, vehicles, ships etc., depicting the technical progress but also the evolution of human ingenuity (Cook and Dennin 1994; Price 2010). They are of great evidential and informational value for the scientific community, but also for large and small corporations, the state, and the public (Schrock 1996; Van der Reyden, Tennison, and Tsai 1996). The importance and usefulness of architectural drawings extends indefinitely in the future, for the lifespan of the structures they depict, and often beyond that. Technical drawings are ubiquitous and plenty. They exist in archival organizations, technical corporations, state organizations, and private collections. Apart from evidential, intrinsic, artefactual, and cultural values, they are also often recognized to possess medium to high artistic value (Schrock 1996).

Technical drawings have been executed on various supports. Tracing (translucent) paper is the most prevalent. It was produced by three main processes (impregnation with resins and oils, overbeating, and sulfuric acid treatment), which defined the appellation of the final products (impregnated papers, overbeaten papers, and genuine parchment papers, respectively) and their properties (Homburger and Korbel 1998; Laroque 2000, 2004; Price 1995; Price 2010; Van der Reyden, Hofmann, and Baker 1993; Wilson 2015; Yates 1984). Tracing cloth, drawing paper and other substrates are also common (Price 2010). A large variety of media were also used, including India ink, iron-gall ink, pencil, crayons, ink washes, watercolors, and felt-tip markers (Price 2010). The need of construction and architecture firms for fast and accurate copy creation led to the introduction of a large variety of photoreproduction processes such as the blueprinting, diazo, Pellet, Van Dyke, and several others (Glück, Brückle, and Barkhofen 2012; Price 1995, 2010; Reed, Kissel, and Vigneau 1995). Original drawings and copies suffer from various types of damage, depending on their intrinsic vulnerabilities, handling, and conditions of storage (Cook and Dennin 1994; Hamill 1993; Wilson 2015; Yates 1984). Because of their size, large numbers, and the coexistence of various types of substrates, photoreproductions, and media in technical drawing collections with different needs and vulnerabilities, the management of such collection is not an easy task.

For the past 30 years, there has been an increasing interest in technical drawings (Alper 1992; Hamill 1993; Price 2010; Tait and Sterlini 1999; Wilson 2015). Important publications and projects have advanced our knowledge on the history, the construction, the materials, the deterioration, the copying processes, the conservation treatments, and the preservation of technical drawings (Glück, Brückle, and Barkhofen 2012; Kissel and Vigneau 1999; Price 2010; Reed, Kissel, and Vigneau 1995; Steiner 1999; Van der Reyden et al. 2011). They also advanced the awareness that they are fragile cultural objects of great importance that need to be preserved.

Greece follows that international trend, and a growing concern is apparent amongst the scientific community, the owners, and the curators of technical drawings collections for their study, documentation, and preservation. Nevertheless, a background search in Google Scholar with the terms “technical/architectural drawings” and “Greece/Greek” returned many results, some concerning ancient Greek architecture, but none of them relevant to the study and management of technical drawings collections in Greece. Relevant literature or lack thereof, personal knowledge, and anecdotal evidence indicate that despite the abundance of such collections in Greece and the increasing interest in them, very few relevant organized initiatives exist. Several organizations, private and public, are known to possess large numbers of technical drawings. However, their accurate numbers, their significance and value, and their condition are largely unknown.

In this paper, we present the survey of one of the collections of historical technical drawings owned by the Historical Archive of Athens Water Supply and Sewerage Company (EYDAP S.A.), aiming at the documentation of the condition of the collection, the determination of the technical specifications, and the cost estimation for its conservation. Apart from presenting an outline of the results of the survey, this publication mainly focusses on the methodology of the survey process itself. It describes the documentation step, which was planned to collect all the essential data necessary for the determination of the technical specifications and the cost estimation of the conservation of the collection. It also presents the process of the cost estimation step. We believe that the methodology described here can be useful and applicable to similar surveys concerning technical drawing collections, and with some adaptations to other archival collections.

2 Background

The Historical Archive of EYDAP preserves various collections of documents, which capture the long and evolving operation of the Company (through the “Hellenic Water Company S.A. of Athens and Piraeus” and the “Greater Athens Sewerage Organization”), and the relationship between the evolution of the water supplying and sewerage systems with the evolution of the Athenian society. The collections include paper documents (administrative, legal, technical drawings and projects), photographs, negatives, audiovisual material, and various objects, which are documented by use of the international metadata standard “Dublin Core”. The Archive applies the internationally suggested best practices for the preservation of the originals and employs a digitization program for the preservation of the digitized collections of historical and cultural value. The constant cooperation with academic institutions, archival organizations, and experts guarantees the effective management of the historical material through the use of best certified practices, which incorporate the required scientific knowledge and set the framework for access and exploitation of the archival material. Since 2018, the “Management Policy of the Historical Archive of EYDAP” is in effect, which sets the rules for the management (including documentation, acquisitions, and preservation) of the Archive and the public access to it.

The Historical Archive of EYDAP owns a large number of technical drawings, many of them related to emblematic infrastructure construction projects such as the Marathon Lake Dam (Figure 1). This publication concerns one of its historical collections, the YAMP (Projects and Specifications Archive Department) historical collection of technical drawings. The curator of the collection, during a quick first survey undertaken in 2017, provided us with the following information:

1. The collection comprises around 2600 important technical drawings dating from 1920 to 1970, with a few newer additions

2. About 70% of the drawings are originals on tracing cloth (Figure 2) or tracing paper, 20% originals on drawing or cartridge paper of various qualities, and 10% copies^[1] (most of them blueprints)

3. The most common size is A0 (approximately 1.20 × 0.84 m)

Figure 1:

Marathon Dam – Drainage system with Foundation Piles – Details of Contraction Joints. Drawing on tracing cloth. © 2021 EYDAP SA Historical Archive. Published with permission from EYDAP S.A.

Figure 2:

Tracing cloth (left), and verso (right). The pattern of the fabric is discernible on the recto. The verso is smooth and glossy.

That first survey (2017) showed that while the general preservation condition of the collection was good, a fair number of drawings suffered from small to medium mechanical damage (mostly tears). A large but unknown number of drawings had a stapled cardboard extension that served as a hanger. Biological damage was not detected.

The collection was stored in a large lobby at the EYDAP headquarters building, housed in four wooden drawer chests with a total of 53 drawers. The drawings were stored mostly flat, sorted in succession according to their accession number, with no dividers between them. Some of the drawers were jam-packed, which could cause mechanical damage to the drawings when the drawers were opened or closed. The environmental parameters were not monitored or controlled.

The documentation of the collection lacked important details. For most of the drawings, only the accession number and the title of the drawing were documented, while an undefined number of drawings were not documented at all. The survey of the collection was commissioned by EYDAP to the Department of Archival, Library & Information Studies, University of West Attica, Greece, and concerns the documentation of the condition of the collection, the determination of the technical specifications, and the cost estimation for its conservation. In this communication, we focus on the survey methodology.

3 Methodology

The survey team comprised two undergraduate students, both in the last semester of their studies, one studying Information Science and the other Conservation, which were trained for the needs of the project and supervised by professor Spiros Zervos. The survey was completed in about two months (October and November 2019), under the supervision of the team’s coordinator. Before the survey, an intern student from the Department of Archival, Library & Information Studies cataloged the collection in ISAD (International Standard Archival Description).

The project started with a thorough literature review, concerning most aspects of technical drawings documentation and management, such as construction, types of substrates, damage, photoreproduction techniques, conservation, and preservation. A lot of time and effort was dedicated to the training of the survey team in identifying the various kinds of drawing substrates, the photoreproduction techniques, the types and degree of damage, and possible conservation treatments. To that end, the contribution of several bibliographical sources must be acknowledged, such as the books authored by Price (2010) and Kissel and Vigneau (1999), the Preservation Self-Assessment Program (PSAP) website (Institute of Museum and Library Services n.d.) and others which will be cited below. Particularly useful was the “Flow-Chart for the Identification of Architectural Archives Reproductions of Drawings and Documents” (Kissel and Vigneau 1999; Reed, Kissel, and Vigneau 1995).

3.2 Cost Estimation

Two factors were considered paramount for the process of cost estimation: automation and parameterization. Automation was important because of the large number of the drawings and the necessary calculations. It can be accomplished fairly easily, since all spreadsheets offer functions that automatically execute basic and advanced calculations. Parameterization was also important because the cost estimation heavily depends on informed assumptions about the person-hours required for each kind of conservation treatment, a matter which is further complicated by differences in the extent and intensity of damage. Cost also depends on the remuneration of the personnel, which is related to the cost of person-hour, which can change. Through parameterization, miscalculations due to wrong assumptions can be very easily corrected by just modifying the relevant parameter.

In order to maximize the usefulness of this paper to practicing colleagues, we will elaborate on the details of both automation and parameterization. To that end, the structure of the spreadsheet will be briefly explained. The documentation fields were used as labels at the top of the spreadsheet. Every category was assigned a different background color for easy orientation in the huge spreadsheet. Each drawing was registered horizontally, constituting a record. Thus, each column of the spreadsheet corresponded to a documentation field, and each row to a drawing.

When documentation ended, the total number of various items, such as the drawings presenting a specific kind of damage, was calculated by use of Microsoft Excel^® formulas. These calculations were done vertically, that is, they applied on the contents of one column.

The next step was the determination of the person-hours required for the conservation of each drawing. To that end, more columns were added to the spreadsheet, each for the person-hours calculation for each type of conservation treatment, plus two for the removal of adhesive tapes and cardboard hangers, and one more for the documentation of the conservation treatments themselves. For every treatment and depending on the severity of the addressed damage, a different value was given to the required person-hours. Here enters parameterization. Instead of setting that value directly to the calculation formula, it was defined once in a different spreadsheet, and a reference to the cell containing the value was used for the calculation. This way, if the value was not realistic and needed to change, the change could be done in one place only instead of 2626 places, the total number of all drawings. Apart from that, parameterization reduces the possibility of errors and makes the whole effort easier to present and manage.

Table 3 summarizes the values of the person-hours required for each type of conservation treatment. Mending, filling gaps, and tape removal person-hours were related to the extent/intensity of the damage (scores 0–3). The rest of the conservation treatments were assigned specific values, independent of the damage scores. Because of the specific nature of the collection, the documented damage, and the conservation treatments (flattening, cleaning, and lamination), it was decided that there was no need for more complexity since significant variations in the required person-hours were not expected. Of course, under different circumstances, parameterization can apply to these conservation treatments as well.

Table 3:

Definitions of the parameters (person-hours), depending on the kind and the score of damage.

Conservation treatment	Score	Person-hours
Mending/filling of losses/tape removal	0	0
	1	0.3
	2	0.8
	3	2.5
Flattening		0.5
Cleaning		0.5
Lamination		2
Documentation		0.1
Cardboard hangers removal		0.2

Concerning the automation of the cost estimation process, some more complex formulas were created that checked if a specific treatment was recommended (by detecting an X in the corresponding cell), and then according to the score of the damage related to that specific treatment, the corresponding work-hours value was used for the calculation.

The assigned values of person-hours were decided after a market research, consultation with practicing paper conservators, and from the personal experience of the coordinator of the project. A medium range of treatment intensity was assumed, between minimal treatment and maximal intervention, which was implied in the project report by the detailed description of each treatment. By the same process, the cost of one person-hour was set. The cost of the materials was also set to 25% of the total cost of person-hours. Both were set as parameters, so that can be easily changed, and the final cost automatically recalculated.

By applying the above-described methodology, the total number of the drawings presenting a specific kind of damage and recommended for a specific conservation treatment, as well as the person-hours needed for the conservation of each drawing were determined (Figure 3), allowing for the cost estimation of the conservation treatment of the whole collection. In summary, 1634 items are scheduled to receive at least one, and a number of them will receive a combination of conservation treatments. The total number of unique treatments will be 2484 and the estimated total person hours 1096.

Figure 3:

Person hours and number of objects per treatment.

4 Brief Overview and Discussion of the Survey Results

A total of 2626 technical drawings were surveyed. The distribution of substrates and copying processes are presented in Figures 4 and 5.

Figure 4:

Distribution of substrates.

Figure 5:

Distribution of copying processes.

The most common media encountered in originals and in additions to photoreproductions included India ink, pencil, various colored inks, watercolors, and felt tip markers.

The general preservation condition of the collection is good. Only a small percentage of drawings suffer from medium to severe damage (scores 2 and 3). In the collection, 137 drawings were rolled and 99 were folded, these will be flattened and stored flat. The types and intensities/extent of damage are summarized in Figure 6.

Figure 6:

Types and intensities/extent of damage.

Most of the damage was manifested as tears and stains. Tracing papers were found to be in a worse condition than the other substrates, with a high percentage of tears and adhesive tapes. Tracing cloth suffered mostly from stains, with fewer cases of mechanical damage. As suggested in the literature, tracing cloth seems to be more durable than tracing paper (Price 2010). Concerning photoreproductions, tears were the main damage of blueprints and diazotypes. Mechanical damage seems to have been caused by poor storage conditions and careless handling. Biological damage, especially that caused by fungi, was not observed.

The average time for the documentation of each technical drawing was 8 min since it took 50 days and 7 workhours per day for a team of one archivist and one conservator to document 2626 drawings.

5 Recommendations

One of the objectives of the project was to suggest best practices for the management and preservation of the collection, which were included in the project report and are briefly outlined here. They pertain to policies, storage and handling of the collection, environmental conditions and personnel, and were based on the relevant literature (Glück, Brückle, and Barkhofen 2012; Hamburger 2004; Price 2010; Steiner 1999; Velensek et al. 2014), common sense, and personal experience.

Concerning preservation, it was stressed that the storage conditions of the collection were inappropriate, and that a new storage facility should be obtained, with appropriate environmental control and monitoring, new housing furniture, such as steel or aluminum plan chest drawer cabinets, and security installations. Concerning the storage practices, the use of archival paper or polyester sleeves and dividers between the drawings was advised.

The proposed conservation treatments, compiled from various bibliographic sources concerning the conservation of technical drawings (Alper 1992; Bedenikovic, Eyb-Green, and Baatz 2018; Cook and Dennin 1994; Ferrari et al. 2018; Flamm et al. 1990; Flieder et al. 1988; Glück, Brückle, and Barkhofen 2012; Hamill 1993; Homburger and Korbel 1998; Laroque 2000; Page 1997; Price 2010; Van der Reyden, Hofmann, and Baker 1993; Yates 1984; Zervos and Alexopoulou 2015), were presented in detail in the project report and will not be included in this article. Washing in water and deacidification were not recommended but were described in the report and left open as options. Literature, experience, and preliminary testing during the survey indicate that extreme caution must be exercised concerning the application of aqueous treatments or adhesives. Careful testing on an individual basis must precede all such applications. This, among others, is a basic precaution applicable to all the recommended conservation methods. The vulnerabilities of the several types of substrates, media and photoreproductions are also stressed in the report, and that the application of water on tracing cloth is out of the question.

6 Conclusions

Concluding this survey, several aspects of the applied methodology must be highlighted:

1. The sources from the literature, which greatly assisted the recognition and correct documentation of the different types of substrates and photoreproductions (Kissel and Vigneau 1999; Price 2010)

2. The importance of the preparation step, which entailed the choice and the accurate definition of the fields used for the documentation

3. The use of existing flowcharts or the creation of new ones for assisting the recognition of the different types of substrates and photoreproductions

4. The need for a trial application of the survey process, which enables optimization and troubleshooting

5. The use of accurately defined values (scores) for the classification of damage, which must be verbally described in detail and if possible, with images and sketches, to ensure uniformity of the results

6. The training of the survey team in recognizing the types of substrates and photoreproduction techniques, and also the types and intensity/extent of damage, as defined by the damage scores

7. The need for automation in the calculations, especially for the cost estimation, by using a spreadsheet and formulas

8. The need for parameterization in the cost estimation, by assigning values for the person-hours parameters and for the cost of person-hour and materials, outside the calculation spreadsheet, and referring to them in it

9. The previous two points require working knowledge of Microsoft Excel^® (or of a similar computer program), or collaboration with an IT specialist

10. The necessity to consult and cooperate with colleagues and the curator of the collection

The total amount of hours, as expected, depends on the values of the parameters in Table 3, and is particularly sensitive to changes in the value of person hours pertaining to damage category (score) 1, since this is the most common (Figure 6). An increase of that parameter from 0.3 to 0.5 increases the total person hours up to 14%. This fact indicates the importance of objectivity in the estimation of the parameters in Table 3, as well as the importance of parameterization.

Concerning the results of the survey, the distribution of the various substrates and photoreproductions were accurately determined. Tracing cloth and tracing paper were the most common substrates (60 and 21% of the 2626 drawings respectively) and from the 764 photoreproductions in total, 434 were diazotypes and 229 blueprints. The distribution of the scores of damages indicates that the condition of the collection is generally good. The most common types of damage are tears and stains. The results of the survey allowed for the cost estimation of the conservation of the collection. They will also be used for the proper storage of the collection, and for the compilation of the emergency plan of the Archive, according to the recommendations included in the project report.