Why no hammered copper coins? Just silver and gold?
I've enjoyed the hammered gold and silver coins posted by many people here including @Weiss and @BillJones. One thing I never thought too much about was why I never saw hammered copper coins. Initially, I thought it was just that copper was not valued enough to be coined, but upon reading the following from Notre Dame, it seems there were technical problems with hammering copper which were resolved by the introduction of the screw press.
Why can't copper be hammered?
A Brief History of British Regal Copper Production during the Seventeenth and Eighteenth Centuries
On Thursday August 1, 1672, Charles II demonetized tokens and announced the government would begin making copper small change coins in a proclamation entitled "A Proclamation for making currant His Majestie's Farthings and Half-pence of Copper, and forbidding all others to be used" (printed in Peck, pp. 605-607). For centuries the crown had produced and continued to mint silver pennies, but they had never issued coppers. With the change from hammer coinage to the use of the screw press the king hoped to be able to profitably make a sufficient number of standardized small change coppers for the country.