thanks, your response makes a lot of sense.
And a big thanks for the link, really interesting. So someone dared to try it and turning the eggs is maybe not as dangerous as most expect.
and i also have something to say about metals: i would stay away from metals. Aluminium is less noble than iron, under certain conditions it rusts and corrodes much faster than iron. Im not a chemist, but what will a bunch of aluminium compounds in direct contact with the eggs do? If nothing serious, at least some local discoloration. Zinc has the same problem. Metal with permanent high moisture.... there is a reason why people have gold teeth, to really be safe when metals touch your eggs you must go for noble metals, or at least a silver coating. Then again, plastics can also spew harmful toxins especially as they decompose. Like PET additives are now under suspicion of causing male fertility issues in humans. Or like certain tubs that can mess up sex ratios when breeding mice or rats in them. The way to handle this is to buy stuff designed for pets, and hoping the manufacturers take that purpose into account when selecting the plastic materials used. Or try to use more natural materials.
p.s.: send an email to http://www.ms-reptilien.de , you know, Stefan Broghammers company, they breed in southern Germany, maybe they can hook you up.