Clear glass allows you to see the colour and clarity of the wine. Glass also has the advantage of being a very poor conductor of heat, so the wine doesn’t warm up too quickly when you grasp the glass. Metal-brass, silver or gold—conducts heat rather too well. Red wine is usually served several degrees warmer that white wine, so a glass for red wine should probably have a well-rounded bottom to provide warming contact between the hand and the wine, if it is needed.
White wine is usually served chilled, so a long stemmed glass will keep the hands away from the wine. The actual bowl of the glass could also be tapered down to a point.
The white wine glass is traditionally slightly smaller than the red wine glass, because with an equal measure of wine in both glasses the red wine has some space left over for the bouquet to gather in.
For sparkling wine use a champagne flute, tall and slim, with only a very small surface area. This way the bubbles will last longer.
It is not necessary to provide separate glasses for the red and white wines (unless the drinker will be having both of course). An all-purpose wine glass works perfectly well for any wine, white or red.
A wine glass—and especially a red wine glass—should never be filled right to the brim. This doesn’t allow the drinker to nose the wine properly without dunking his or her nose in it.
Select a wine glass big enough to give a generous helping when it is about two-thirds full. Finally glasses break—for this reason keep your very expensive glasses for rare and dignified occasions.