Iso din 9706

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Required These cookies are essential for the operation of the site and enable, for example, security-relevant functions. Confirm selection Select all. This problem is best set out by quoting from ISO itself:. The reason for this is that in the uses envisaged for the papers, some loss of brightness or slight yellowing is less important than retention of mechanical strength; a certain degree of discolouration can be tolerated before most printed material becomes illegible.

It was therefore considered that the added complication of specifying optical tests was unnecessary, especially as accelerated ageing tests would almost certainly be needed, including exposure to light. The lignin produces acids as it degrades, thereby introducing a destructive force into the paper.

Close questioning of the manufacturer reveals that the term acid free is used because they do not add any acids during the production process and add some Calcium Carbonate buffering.