This paper presents objectives and realization of conservation treatment of three 18th century bound herbaria from Polish collections: the herbarium of Izabela Czartoryska, 1746 (National Museum in Cracow), the herbarium of Johann Friedrich Zeidler, 1732 (Library of the University of Life Sciences in Lublin), and a herbarium by Matthias Boretius and/or Andreas Helwing, 1725-45 (Herbarium of the University of Warsaw). All three items count among the oldest surviving herbaria in Poland.
Although they were created in the same time period, herbaria present different styles and techniques. Their poor condition before treatment prevented any research and safe handling. As valuable historical documents, they also required careful treatment planning, regarding their scientific, historical, and possible exhibition values.
Ethical considerations included the strategy for detached and loose plants, choosing the right adhesive to re-attach specimens, and adjusting paper conservation procedures to the delicate and deteriorated structure of herbaria. In the cases of Zeidler’s and Boretius/Helwing’s herbaria, most of the treatment was executed without disassembling the blocks.
In herbaria of Czartoryska and Zeidler recognizable fragments of specimens were attached to the pages where they were mounted previously, and the rest of plant remains were put in the envelopes. The envelopes were not attached to the pages but were put in transparent enclosures. The adhesives used to mount the plants and repair the paper were chosen, basing on the test of adhesives concerning the safety for DNA material.
In the case of Boretius/Helwing’s herbarium, loose plant specimens were spread throughout the tightly sewn block and most of them were deformed and broken. The decision made with the curator was to remove the specimens, mount them on the new sheets, and treat the album separately to keep it empty as the archival record.
Another challenges were treatment of iron gall ink corrosion and consolidation of paint layer on some specimens in Zeidler’s herbarium.
These conservation treatments were a part of the project „Heritage preservation and ethnobotany. Analysis of the influence of conservation treatment on genetic material of historic herbaria“ (project no. 2014/13/N/HS2/03118) funded by the National Science Centre in Poland.