There are now more and more cheap Chinese "black" ZWB1, ZWB2, ZWB3 Filters for reflected UV photography on the market, but CAVEAT:
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Klaus,
This obvious “fault line” is both amazing shocking for a scientific product!
It looks like the temperature of molten glass was lowered too fast and was uneven in cooling so waves occurred and were preserved like a frozen larva flow by a volcanoes!!
I have only seen that on very old windows!
China has problems like this with QC. I know a company that routinely buys from China gear parts then re-machine the surface accurately to finish them off so meet tolerances!
But there's another serious issue. While major beating MFRs might produce some of the most critical bearing assemblies in China for Western markets, the supply chains also have numerous independant “producers” and the steel may or may not meet specs of the original.
In my sculpture, going your “Schott/Hoya ONLY” way, I sourced by SKF bearings from Austria to make sure they would obey the safety standards needed for massive public art structures.
China should have a standard of approval we could rely on for high tech critical engineering, pharmaceutical and other parts!
Perhaps they do?
For cheap plastic bowls and chairs, using recycled scrap plastic shipped from around the world doesn’t matter! But for serious science, health and safety they are still unreliable.
Asher
