Pablo, Might I ask how you came by your enamels and what you are
trying to do w/ what you have? The way you have worded your
questions it sounds almost like you stumbled across a random jar of
enamels and decided to take it out for a spin. Have you worked w/
enamels at all? What type of jewelry do you do? Have you done any
research or reading on enamels? Your questions have a large number of
variables. Size of piece, type of enamel, what effect you are
looking for, what metal you are working w/, along w/ several other
questions. There are a number of resources on the web for enameling
including the archives from ganoskin. I would suggest you review
the archives from this list, and do some web searches for enamel.
Also, if you have any access to enameling books to borrow or even
purchase I would recommend you glance at them.
If you wish to answer some of the above questions, it will help
considerably in providing you w/ what you need to do what you want.