Obtaining Damaged Slides

Very often the amateur may come upon the opportunity to obtain significant quantities of prepared slides of a type that makes use of methods or materials that are not generally within the scope of ones own activities. Such slides may provide valuable objects for study. Regrettably, one may find that many slides prepared in professional circumstances only find their way onto the market at excessive cost or when damage sustained in one way or another has rendered them unsuitable for study.

Recently a quantity of slides were obtained by the author that consisted of serial sections from Leptonycteris sp. The exceptionally thin and expertly stained sections were mounted in series under rectangular 18x40mm or 24x50mm coverslips. All of the slides showed degradation of the mountant to a greater or lesser degree characteristic of repeated stress from heating and cooling.

Due to the visible damage 75 individual slides were had for the incredible price of ten United States dollars. One would be hard pressed to obtain a similar number of blank slips or coverslips for the same price.

Assessing the Damage

Visibly degraded mountant, black background.

Initial observation showed that the slip was in fine condition without chips or cracks which would greatly complicate the task of rehabilitation. Despite the significant degradation of the mountant the cover slip remained firmly in place, a good sign that the sections beneath would be intact. Running a fingernail over the cover is often all that is required to determine if the coverglass itself is similarly undamaged.

Visual inspection showed the mountant to be significantly degraded on most of the slides. Pronounced yellowing at the edges gave way to white patterns where mechanical damage had caused the mountant to crack to an extent that it was no longer in optical contact with the coverslip. In some instances the mountant had become brittle to the point that the coverslip had come off entirely. The areas occupied by the specimen were invariably damaged even in places where the surrounding mountant remained sound, as may be seen at the extreme right of the image at left.

Under the microscope one could observe the extensive cracking of the mountant shown below. Focusing on the specimen with a 16mm objective was nearly impossible as the depth of focus afforded by the objective ensured that the cracked mountant would intrude into the image plane. At higher levels of magnification one could optically section the image enough that the cracks were not immediately evident, but resolution was impaired to the point of near total occlusion of any detail.

Photomicrograph showing degraded mountant.