Apparently they did have documentation for how to manufacture FOGBANK, but when they rebuilt the manufacturing pipeline the end product didn't pass the tests.
After some debugging they realized that back in the 70s, one of the raw materials had been purified to a lower standard than today, and one of the contaminants actually turned out to be crucial to the process. Once they knew that, they could start intentionally adding that contaminant and track the concentration of it.
Apparently they did have documentation for how to manufacture FOGBANK, but when they rebuilt the manufacturing pipeline the end product didn't pass the tests.
After some debugging they realized that back in the 70s, one of the raw materials had been purified to a lower standard than today, and one of the contaminants actually turned out to be crucial to the process. Once they knew that, they could start intentionally adding that contaminant and track the concentration of it.