Introduction
In 2019, The Corning Museum of Glass (CMoG) performed a complimentary elemental analysis of UW Blaschka glass shards to determine the chemical composition of glass used by the Blaschkas in the mid-to-late 1800s. Five samples were given to the Corning Museum for analysis. These samples included clear shards from hollow glass bubbles, clear solid glass pieces, colored yellow beads, and a clear outer bulb with a colored inner bulb. The outer bulb was separated from the inner bulb for analysis.
Analysis
To conduct their analysis, scientists Jesse Kohl and Ela Bakowska at the Corning Museum of Glass performed a gentle cleaning of each of the samples provided by the University of Wisconsin-Madison. Following this cleaning, the samples were ground to a fine powder as preparation for analysis.
The following analytical techniques were used on the glass samples:
- Semi-quantitative analysis
- High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS)
- Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES)
- Quantitative determination of major and minor elements
- Flame Atomic Emission Spectroscopy (FE)
- Quantitative determination of K, Na, and Li
- Quadrupole Inductively Coupled Plasma Mass Spectrometry (Q-ICP-MS)
- Quantitative determination of minor, trace, and ultratrace elements
Findings
The analysis found that the glasses used by the Blaschkas in the mid-to-late 1800s were chemically similar to soda-lime (soft) glasses commercially available today. In addition, Lead (II) oxide (PbO) was identified as a source of the yellow color on the yellow beads provided by the UWZM.
2023 Update
In 2023, glassblower Aaron Kirchoff (Strong Force Glass) generously created two batches of glass rod based on the chemical composition of “Glass #1: Clear Hollow” from Corning’s 2019 ICP high resolution mass spectrometry analysis. The first batch excluded arsenic, known as a color blocker and fining agent, due to health and safety issues with the chemical.
The first one-pound batch of glass was a strong plum color, which Kirchoff determined was due to the manganese content of the glass in the absence of arsenic. Kirchoff believes that manganese was originally introduced to the batch to function as a decolorant of iron contamination from impure silica. It is believed that the silica mined 100-150 years ago was not as pure as silica mined today and likely contained higher amounts of iron contamination.
Based on the belief that silica today is purer than silica used in the 1800s, Kirchoff created a second one-pound batch of glass that omitted both manganese and arsenic. The resulting glass from this batch was clear in color, supporting the theory that manganese was used to combat discoloration from iron contamination.
This glass will be used in future research surrounding the recreation of Blaschka invertebrate models.
