For collectors EBAY, antique stores, and flea markets are popular places to find insulators.  There are many unscrupulous sellers that will alter the insulator colors to make them more attractive and thus more valuable.  There are a number of ways alteration can be done, but one of the most common is to use glass stains to coat the insulator to make it a different color.  When done well these stains can look very good and be hard to visually detect.  Scratching the glass with a sharp knife or razor will usually show the coating.  Many of the sellers actually admit to the staining process but do so in an obtuse way to confuse buyers.  Look for the following key phrases:

 Some examples are shown below

Group of stained insulators

Pink stain & crackle

purple stain

Cobalt heat stain


Key recommendation is to get educated -- there are many excellent books available as well as lots of insulator shows.  Shows are a great place to meet other collectors face to face and possibly find a local mentor.  There are also some more subtle methods of altering the color of insulators as can be seen in the link below


Artifically Induced Colors



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