"I love making my own chocolate candies and use the
water bath method to melt chocolate. From time to time
the steam from the pot under the bowl gets in the chocolate
and then it seizes up and ruins. What causes this and
how can I repair the damage?"
Chocolate was once considered to be the food of the ancient
gods, so perhaps one can expect it might have some idiosyncrasies.
As you've found out, melting is one of them. Sometimes
chocolate melts to a satiny pool of liquid chocolate,
and sometimes it becomes a grainy mess.
Chocolate being melted, simply can't tolerate small drops
of water. In this case, the steam escaping from the bottom
of the double boiler is sufficient to make chocolate seize.
The same thing will happen if you cover the pan in which
chocolate is melting. Then moisture condenses on the inside
of the lid and drips down on the melting chocolate...
with the same result.
Once chocolate has seized it's not easy to coax it back
to liquid form. Sometimes whisking a tablespoon of warm
water into the chocolate works, then add more water a
teaspoon at a time until the chocolate is smooth. Or try
adding a few drops of vegetable oil or clarified butter
(as it's water content has been removed). This will sometimes
soften the seized chocolate enough that it will mix with
other ingredients. Resurrecting it is always worth a try!
When melting chocolate make sure the water in the bottom
of a double boiler is hot, but not boiling. Or consider
melting chocolate in a very heavy saucepan with a metal
ring placed on the element to insulate it from direct
heat. The temperature of the chocolate should not rise
about 115° F (46C), which is only as warm as tepid
water. A microwave set at only 50% power, and checking
it every 90 seconds, also works well. When it's "almost
melted" the carry-over heat held in the chocolate usually
finishes the job.
As strange as it seems, when larger amounts of water are
used, the dynamics of melting change so that chocolate
liquefies smoothly. When a recipe calls for melting bittersweet,
semisweet, or white chocolate WITH liquid, use a minimum
of 1 Tablespoon (15 ml) of water per ounce of chocolate.
For unsweetened chocolate some sources recommend using
at least 1 1/2 Tablespoons (20 ml) water per ounce.