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Molding samples from gels
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Photoelastic samples can also be cast from more common materials than [urethane](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/molding-urethane). For example gelatine is a very good photoelastic material, with a high photoelastic constant, which means a small stress induces a large photoelastic effect. [picture]
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Photoelastic samples can also be cast from more common materials than [urethane](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/molding-urethane). For example gelatin is a very good photoelastic material, with a high photoelastic constant, which means a small stress induces a large photoelastic effect. [picture]
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The different photoelastic gels
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Gelatine is most likely the most used photoelastic gel but many others like agar or konjac exist [[Tomlinson and Taylor](https://www.spiedigitallibrary.org/journals/Optical-Engineering/volume-54/issue-8/081208/Photoelastic-materials-and-methods-for-tissue-biomechanics-applications/10.1117/1.OE.54.8.081208.short?SSO=1)]
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Gelatin is most likely the most used photoelastic gel but many others like agar or konjac exist ([Tomlinson and Taylor](https://www.spiedigitallibrary.org/journals/Optical-Engineering/volume-54/issue-8/081208/Photoelastic-materials-and-methods-for-tissue-biomechanics-applications/10.1117/1.OE.54.8.081208.short?SSO=1))
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Making cross-linked gelatine discs
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Making cross-linked gelatin discs
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Gelatine discs can be molded in the same way as [urethane](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/molding-urethane) discs. To make gelatin discs, first dissolve gelatin in water. Depending on the required rigidity, the concentration of gelatin can be tuned. A typical concentration is 10 weight percent. It helps to first heat the water (e.g. to about 60 degrees Celsius) before adding the gelatin, to help dissolve it. The gelatin will set at a temperature around 35 degrees. After pouring the warm gelatin solution in the rubber molds, store the molds in the refridgerator for around 3 hours, to make sure the gels are fully set.
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Gelatin discs can be molded in the same way as [urethane](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/molding-urethane) discs. To make gelatin discs, first dissolve gelatin in water. Depending on the required rigidity, the concentration of gelatin can be tuned. A typical concentration is 10 weight percent. It helps to first heat the water (e.g. to about 60 degrees Celsius) before adding the gelatin, to help dissolve it. The gelatin will set at a temperature around 35 degrees. After pouring the warm gelatin solution in the rubber molds, store the molds in the refridgerator for around 3 hours, to make sure the gels are fully set.
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After removing the gels from the molds, place them in a 10 weight percent glutaraldehyde solution for about 2 hours. This cross-links the gels, so that they will no longer dissolve in water. Glutaraldehyde is toxic, so make sure to use gloves. Other cross-linkers do exist, but not all of them retain the photoelastic properties of the gelatin. Remove the gels from the glutaraldehyde solution, and wash them repeatedly with water, by leaving the gels in an excess amount of water for at least 12 hours. Repeat the washing procedure a few times to ensure all glutaraldehyde is washed away and diffused out of the gels.
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After removing the gels from the molds, place them in a 10 weight percent glutaraldehyde solution for about 2 hours. This crosslinks the gels, so that they will no longer dissolve in water. Glutaraldehyde is toxic, so make sure to use gloves. Other crosslinkers do exist, but not all of them retain the photoelastic properties of the gelatin. Remove the gels from the glutaraldehyde solution, and wash them repeatedly with water, by leaving the gels in an excess amount of water for at least 12 hours. Repeat the washing procedure a few times to ensure all glutaraldehyde is washed away and diffused out of the gels.
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[<go back to home](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/home) |
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