Chocolate – How to thin chocolate for dipping

I can think of at least three things that will cause chocolate to seize - which refers to when melted or melting chocolate suddenly becomes hard again:

• Using too high a heat. Double-boiler is the safest, but you can use a saucepan on very low heat.

• Sugar bloom and other impurities. You shouldn't get this with baker's chocolate, but if you use any lower-quality chocolate, this can seep into the melting chocolate and cause it to seize.

• Contact with moisture! Even a tiny amount will cause it to immediately seize, and it's difficult to recover at that point.

Sounds like you fell into traps #2 and #3 and possibly #1. I would not melt chocolate in margarine; I'd even be wary of melting it in butter, and find it strange that a recipe would call for that, because both butter and margarine contain water!

Melting chocolate in a liquid can actually help prevent seizing, but you have to use a lot of liquid and the liquid has to be completely melted before you start trying to melt the chocolate. It's better to use something like a vegetable oil which has no water content if this is what you're trying to do.

So, in summary:

• Definitely stay away from the margarine. Even if you need to use butter, make sure it's completely melted first and try to use only the fat (clarify it).

• If you can, melt the chocolate and clarify the butter separately and then whisk them together gradually afterward; not only will this help to prevent seizing, but if commenter @roux is correct and the problem isn't one of seizing, this will still help to guarantee that the chocolate melts evenly.

• Use the best quality chocolate you can find. Chipits are generally OK to melt on their own, but if they've been sweetened then this may contribute to seizing if other factors are present.

• Melt in a double-boiler or on very low heat.

Very simple: don't store your chocolate in the fridge. The ideal temperature for setting chocolate is 20°C. You can store it at less or more than that, but not too much. Setting in the fridge results in bad chocolate. Remember, when you work with chocolate, exact temperatures are extremely important.

Here a loose translation from a good article on chocolate/couverture coating:

This is the usual case. You only want a temperature difference of 12° to 13° between the chocolate and its environment as well as between the chocolate and the confect interior.

If the interior is colder than the room, the setting will happen "inside out". The cocoa butter film which gives a confect its shine will build on the inside, leaving the outside looking dull.

This is a really good case for some types of confect, but you can't do it with most types of filling (definitely not with strawberries). Cooling from the outside gives you a beautiful shine.

If you want to achieve a good shine, it is possible to put the confects in the fridge for a short time, but only after they have cooled to 20°C at room temperature. Don't let them fall to fridge temperature, take them out at 15°C. The continued cooling from the outside is beneficial.

This shouldn't happen. The temperature difference is too small, and the confect doesn't set quick enough. In this case, cocoa butter pools on the surface and creates a yellowish layer after it hardens.

When you make your confect, you should time the first piece. The setting should need 10 minutes. If it is less, you don't get all the possible shine. If it needs more, it will get grey or whitish yellow.