Re: Why does instant Sanka coffee stain a cup more than regular sanka?

> Why does instant Sanka coffee stain a cup more than regular sanka?

This is a very interesting question, but first I must ask: What 
experiments have you done to convince yourself that instant coffee 
actually DOES stain a cup more that regular coffee?  

The reason I ask is that I always drink regular coffee, while my wife 
drinks instant.  I wash most of the dishes in my house, and I've never 
noticed any difference.

For the sake of argument, let's say however that your hypothesis is true.  
The instant coffee making process basically consists of making coffee and 
then taking the water out in such a way as to "instantize" the remaining 
solids so that they rapidly rehydrate when placed in water again.  There 
may be something about the drying process that make the color molecules 
(probably tannin's) more "sticky" and likely to stain.

One place to go, where you may be able to find our more would be this book:

Personal Author:  Sivetz, Michael.  
Title:  Coffee technology / Michael Sivetz, Norman W. Desrosier.  
Publication info:  Westport, Conn. : AVI Pub. Co., c1979.  

Good luck!