Insights
How a specification gets lost
Specification drift is rarely a decision. It is a series of small, individually defensible substitutions, each made by somebody with incomplete information and a deadline.
The pattern is consistent enough to be worth naming.
Published
It starts as a requirement and becomes a product name
The engineer knows the material has to tolerate a temperature and be compatible with a substrate. What gets written down is the name of the product that happened to satisfy both, because that is shorter.
From that point on, the requirement is invisible. Anyone comparing options is comparing them to a product name rather than to what the product was chosen for, and the reasoning is no longer available to be checked.
Then the grade falls off
Grades are the part most often lost in transcription, because they look like a suffix rather than a fact. Technical and reagent grades of the same substance share a name and a CAS number and are not interchangeable.
A purchase order that names the substance without the grade will eventually be filled with the cheaper one, correctly, by a supplier who was never told otherwise.
Then someone helpfully substitutes
A substitution offered in good faith — same substance, different supplier, better price, available sooner — is only assessable against the original requirement. Against a product name, it looks equivalent.
This is the step where the error becomes invisible, because the substitution was approved. Everybody did their job.
The fix is boring
Write down what the item has to do, not only what it is called. Keep the grade attached to the name everywhere the name appears. Require that any proposed equivalent be justified against the requirement rather than against the previous purchase.
None of this is sophisticated. It is just the part that gets skipped when procurement is treated as a transaction rather than as a record.