A question came up today about when to use hard, medium, and low firing enamels.

Hard firing enamels are fired at a higher temperature as in the 1500’s degree range or longer in the kiln.

Medium firing enamels I think of using in 1400’s degree range, or at higher temp as 1500 degrees, but less time.

Low firing enamels maybe fired in the 1300’s or even in the 1400’s with less time.

The purpose of all this is to balance two things.

First the  expansion of the metal being used.

Second your technique being used.

Starting  with copper as it is used most commonly in enamels.

Copper oxidizes the fastest of the metals we use in enameling. We balance this by using medium firing enamels so they melt or fuse before the copper has time to oxide. And using higher temperatures. If it oxidizes the enamel is likely to flake off or just discolor, but many enameling on copper use the oxidation to get some beautiful colors.

Another way to balance this is to use finer grit of enamel. The finer grit will fuse quicker than a larger grit of enamel without allowing oxygen to get to the copper. Without oxidation the enamelist  achieves that beautiful gold or stunning golden orange copper color.

It is best to know the fusing points of all your enamels not only so you know which ones to apply as a base coat of enamel known as flux, which should be the hardest enamel, to avoid the lower layer to rise above the secondary layers as seen below.

1)

Low firing enamels vs high firing enamels

Above the flux was a lower firing enamel than the top coats. So as the top layers melted the flux rose up along the edges and the top layer of enamel puddled in the center.