In this context, the Eutectic Effect is the result of silver combining with copper to form a new alloy, which has a lower melting temperature than either of the two original metals. This used to be considered an error, but is now made into a technique. Averill B. Shepps wrote the project in the book, which tells how to somewhat control how the new alloy is shaped. This control is based on enamels with Chromium in them (these inhibit the effect).
The project in the book says that some of the greens and maybe some browns have Chromium, but it is left to the reader to test which work for this purpose. These Thompson Enamel enamels, provided by Jean Tudor, have Chromium and thus should be tested firs (listed highest to lowest)t:
These Thompson Enamel enamels have Potassium Dichromate which is an inorganic compound that emits toxic chromium fumes upon heating. Potassium dichromate is highly corrosive and is a strong oxidizing agent. it is not clear if these work to inhibit the Eutectic Effect, but it is left to the reader to test. But be careful - use good ventilation as heating these enamels can release toxic fumes. These are listed with highest amount to lowest:
if you try any of these, I would appreciate if you contact me to discuss your results so I can post them here.