Terminology

A term perhaps worth knowing more about:  “tropicalised”.  

This term is commonly used to describe alterations that effect the original gum on a stamp.

Tropicalised gum occurs when the original gum undergoes an alteration. This alteration can happen because of various factors, including

–         
softening and reforming: the gum may become soft and then harden again, often while a stamp is in a plastic mount or album.   In some case this may show as what might be termed a wrinkling of the gum.

–         
discoloration: the gum may change colour from its original state, for example  gums that show a yellowing colour can be quite commonly seen in early 1900 stamps.

–         
Interleaving adhesion: sometimes interleaving – that is the paper used between stamps in an album – adheres to the gum affecting its appearance. A common feature we might see are small pieces of black page remnants on the gum.

–         
fungal growth:  something we all have seen  from time to time and are more likely to  know if it by such terms as foxing, or toning is the condition where the stamp gum condition shows brown spotting and discolouration.   Conditions  such as high humidity, especially accompanied by poor storage can cause this type of change in gum condition. Perhaps also worthy of note here, some gums are more prone to being effected.  I won’t try to list them all as I will miss  some I am sure, but you might think of  mid 20^th century stamp issues from Papua New Guinea,  Malta,  Germany DDR, Rhodesia,  and many Eastern European countries just to  list a few.  No doubt you know many more.

 So, in summary, when a stamp  condition is  stated as tropicalised it is meaning the gum condition  has been altered from its original condition with most likely notable discolouration or other visible changes.