Why did my epoxy overheat and turn yellow?

Epoxy releases heat when curing. EcoPoxy makes recommendations for maximum project volumes and/or thicknesses to allow projects to shed heat efficiently and  prevent overheating and yellowing. If the recommended maximum pour depth and volume are exceeded, the epoxy will not be able to shed heat quickly enough, and the temperature will increase uncontrollably. Cure temperatures that reach 100°C (212°F) for extended periods are known to cause yellowing, and extremely high temperatures can cause epoxy to amber and form cracks. If a deeper pour is required for a project, it is recommended to pour multiple layers to build up to the desired final thickness.