Fired Products — Underglazes

Fired Products come in three types: underglazes, glazes, and overglazes.

  • Underglazes are basically colored slip and also come in three types which we will talk about today. They are painted onto greenware or bisque and fired (first firing–usually to cone 04). Then a glaze is applied over top, usually clear glaze, and fired again.
  • Glazes come in many types and are painted directly onto bisque before firing. This topic is for another day. All glazes need to be fired (second firing), usually to cone 06.
  • Overglazes include products that go over an already-glazed piece. They include metallics, Mother of Pearl, china paint, and decals. They are then fired again (third firing) to a cooler temperature (017-020).


Since we are Certified Duncan Teachers, we use primarily Duncan products which are referred to in this post. Mayco and other companies have similar products which can also be purchased at Ohio Ceramic Supply in Ravenna or other ceramic distributors around the country.

cuncan-cover-coat-picture.jpgCover Coats

This underglaze product had been around since before we started ceramics in 1970. It is primarily colored slip in a jar, that is made to use on greenware. Three coats are needed for complete coverage. Cover Coats can be used on bisque if you first paint on a wash of 50% color and 50% water. It provides more solid coverage that Concepts.

0001793_duncan-cover-coat-opaque-underglazes-tile-chartDuncan Cover Coat




This product has also been around for many years and is used for detailed decoration where you want a translucent effect, think of watercolors.

EZ stroke color chartDuncan EZ stroke



This product was designed for use in the current market where most people buy ready–to-paint bisque pieces. Concepts is painted directly onto bisque. It is not for use on greenware. The numbering system for Concepts is unique and makes choosing different shades quite easy. For example, light straw is 011, bright straw is 012, and dark straw is 013.  In most applications, Concepts can take the place of both Cover Coats and EZ strokes as one coat is translucent and three coats is opaque. However, you must take care if you want solid coverage as it is easy to get streaks.

Duncan concepts color chartDuncan Concepts

Color tile charts and underglaze descriptions are from the Duncan website. Today’s post is to familiarize you with the different types of underglaze and their uses.

Carol’s Carousel
Where having Fun is why we come!

Next up will be different projects and techniques with underglazes.

This entry was posted in Upcoming Workshops. Bookmark the permalink.

2 Responses to Fired Products — Underglazes

  1. Mary S says:

    If cover coats are from 1970s ,when did e – z strokes come out . and when did concepts get introduced?
    Ya. Someone has to ask .


    • You can probably get this information from one of the Duncan Ambassadors, e.g. Larry Knight or Dru Woodward. Cover Coats is opaque and EZ strokes is translucent. I have been using both forever and we started in 1970. booth are for greenware but can be used on bisque with certain instructions. Concepts was introduced when everyone started buying bisque.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s