Inclusion

An inclusion is a tiny piece of foreign material that was in the wood pulp slurry used to make paper. So, it is throughly imbedded in the paper and cannot be removed – don't even try.

It could be any impurity, but this is most commonly a dark bit of tree bark that could not be bleached out in the papermaking process. It is disfiguring to some degree and will affect the grading of very high quality stamps. Otherwise, it could be something to avoid when buying stamps or just something to live with. Then again, if you always resort to very high magnification and look hard enough, you will always find inclusions and flaws in wood pulp paper. You will never buy a single older stamp. Plus, there are issues that never free of impurities. Inclusions of one kind or another are sometimes a key to confirming certain issues. 



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