[Nhcoll-l] crack formation in glass stoppered jars on display

[Simon Moore]

Hi Ian,

The cracking is caused through internal stresses in the glass that build up over years, especially in jars that are over 100 years old.

The cracks can be repaired, one jar surface at a time, using HXTAL resin which is a slow-setting (3 days) and liquid resin so that it has time to penetrate inside the cracks.

With all good wishes, Simon.

Simon Moore MIScT, RSci, FLS, ACR
Conservator of Natural Sciences and Cutlery Historian,
www.natural-history-conservation.com 




On 04 Jan 2017, at 23:19, Ian Hart <ihart at calacademy.org> wrote:

> We have had tadpoles (mounted on glass slides) on display in old ground-glass stoppered jars containing 10% formalin since September 2014. In the last 6 months (of 2016) two of these jars have developed (apparently) spontaneous cracks in the neck of the jar. Nothing could have struck the jars from without.
> 
> Has anyone experienced cracks like this? If so, were you able to find out what caused them?
> 
> We want to put the specimens back on display, but would like to rule out the display environment as a contributing factor to the cracking problem. The jars are on display in an illuminated cabinet. We do not have case temperature data for the time that the cracks occurred, but we have subsequently recorded a maximum daily temperature fluctuation in the case of 4.25 deg F (from 70.803 deg F to 75.075 deg F)
> 
> I would gratefully appreciate any relevant information you have to share on this subject.
> 
> --- 
> Ian Hart
> 
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