HILDEGARD HOMBURGER BARBARA KORBEL - Architectural Drawings on Transparent Paper - Modifications of Conservation Treatments

Oct 28, 2026

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Conservation treatments for twentieth-century German architect Hugo Häring’s architectural drawings on transparent papers are examined as a case study in paper conservation. The text explains how damage emerges from both use and the intrinsic properties of different papers, and describes preparatory assessment of dirt, discoloration, brittleness, creasing, tears, and losses. It outlines transparent-paper production methods—impregnated, acid-treated vegetable parchment, and overbeaten fibers—and connects material identification to choosing treatment approaches such as isinglass use, pulp filling for tears, and hard-soft sandwich flattening.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages9

Reading Time23 min

AccessFree to download

Architectural drawings on transparent paper

Material properties and conservation challenges

Production methods for transparent paper

Impregnated and prepared tracing/vellum papers

Genuine vegetable parchment paper

Paper from overbeaten fibers

Imitation parchment, natural tracing, and glassine paper

HILDEGARD HOMBURGER BARBARA KORBEL Architectural Drawings on Transparent Paper Modifications of Conservation Treatments Drawings on transparent paper are a common working medium for architects. Damage arises through use but it is also related to the particular qualities of the papers. Through the conservation of twentieth-century German architect Hugo Häring’s architectural drawings, known paper conservation methods have been further developed. Methods we will discuss include the use of isinglass, the application of paper pulp to tears, and flattening in what will be called a “hard-soft”sandwich. Hugo Häring (1882-1958) was a member of “Der Ring,” an important architect group in Berlin . Famous architects like Mies van der Rohe, Walter Gropius and Hans Poelzig were also members. Häring developed the idea of “organic architecture”and built several important buildings of which the Gut Garkau, a farm building near the city of Lübeck, is the most famous. The designs of Gut Garkau and the hospital Gaffre Guinle in Rio de Janeiro are part of the estate of Hugo Häring which is kept in the collection of the Akademie der Künste, Berlin (figs. 1-2) . The drawings on tracing paper from this estate were chosen for conservation treatment. They dated mainly from the 1920s. The Fig. 1. Gut Garkau, before treatment: pressure sensitive tape, tears and losses. Fig. 2. Hospital Gaffre Guinle Rio de Janeiro, before treatment: creases, tears and losses. The Book and Paper Group Annual 18 1999 26 The Book and Paper Group Annual Vol. 18 1999 designs are drawn in chalk, ink, and pencil on vegetable parchment paper and impregnated transparent paper. Prior to treatment, all the drawings were slightly dirty and had the expected damage for such papers. The impregnated paper was badly discolored, the vegetable parchment slightly stained. The paper was brittle and creased and had numerous tears with pressure-sensitive tape attached to therecto and verso. Many of the drawings had losses ofvarying size. When working with these papers it was necessary to identify the different types of transparent paper and their special qualities. Therefore, the different production methods will be brieﬂy introduced. PRODUCTION METHODS Paper consists of a network of ﬁbers. The single cellulose fibers, which themselves are transparent , are surrounded by air. Falling light is scattered by this air and that is why paper is opaque. In order for the paper to be transparent the air has to be displaced by a material which has an refractive index similar to cellulose. The light is then transmitted rather than scattered. In the history of papermaking, three well-known methods were developed in order to achieve transparent paper: impregnating, acid treating, and overbeating. Each method is brieﬂy discussed here. Impregnated Paper/Prepared Tracing Paper/Vellum Paper For many centuries paper was impregnated with materials that had a similar index of refraction such as linseed oil, poppy-seed oil, starch, varnish etc. (Mills 1986; Flieder et al. 1988). Today starch, mineral oils, and synthetic resins are used to raise the transparency of paper (Van der Reydenet al. 1993) . Genuine Vegetable Parchment Paper From the middle of the nineteenth century, paper was made transparent through treatment with acid, mainly sulfuric acid. Through the effect of the strong acid, a coating of colloidal cellulose is produced on the fibers which is insoluble in water, fills out the pores in the paper, and makes the paper translucent and similar to parchment. An alkaline neutralization bath follows the acid treatment. Then the paper is calendered so the remaining air in the paper continues to be reduced. As a result of the acid treatment the paper reduces in size and becomes a high quality, strong paper with especially tear-resistant qualities in wet situations and a matte surface. Until the nineteenth century, paper pulp was made mainly from cotton and/or linen ﬁbers; lat

FAQs

What kinds of damage are described for the transparent drawings before treatment?

The drawings are described as slightly dirty, with discoloration of impregnated paper, staining of vegetable parchment, brittleness, creases, tears with pressure-sensitive tape, and losses of varying size.

Why is identifying the transparent-paper type necessary for conservation?

Different types of transparent paper have distinct production methods and special qualities, so conservation choices depend on correctly identifying the paper material.

Which production methods for transparent paper are discussed?

The text discusses three main methods: impregnating, acid treating, and overbeating of paper fibers, each briefly explaining how transparency is achieved.

Oct 28, 2026

Upload by Aran